Merge pull request #134 from launchbadge/derives

Add derives to support custom types

Cargo.toml

@@ -92,6 +92,10 @@ required-features = [ "mysql" ]
 name = "mysql-raw"
 required-features = [ "mysql" ]
 
+[[test]]
+name = "mysql-derives"
+required-features = [ "mysql", "macros" ]
+
 [[test]]
 name = "postgres"
 required-features = [ "postgres" ]
@@ -105,12 +109,9 @@ name = "postgres-types"
 required-features = [ "postgres" ]
 
 [[test]]
-name = "mysql-types"
-required-features = [ "mysql" ]
+name = "postgres-derives"
+required-features = [ "postgres", "macros" ]
 
 [[test]]
-name = "derives"
-required-features = [ "macros" ]
-
-[profile.release]
-lto = true
+name = "mysql-types"
+required-features = [ "mysql" ]

sqlx-core/src/database.rs

@@ -9,7 +9,7 @@ use crate::types::TypeInfo;
 /// A database driver.
 ///
 /// This trait encapsulates a complete driver implementation to a specific
-/// database (e.g., MySQL, Postgres).
+/// database (e.g., **MySQL**, **Postgres**).
 pub trait Database
 where
     Self: Sized + Send + 'static,
@@ -29,21 +29,54 @@ where
     /// The Rust type of table identifiers for this database.
     type TableId: Display + Clone;
 
-    type RawBuffer;
+    /// The Rust type used as the buffer when encoding arguments.
+    ///
+    /// For example, **Postgres** and **MySQL** use `Vec<u8>`; however, **SQLite** uses `Vec<SqliteArgumentValue>`.
+    type RawBuffer: Default;
 }
 
+/// Associate [`Database`] with a `RawValue` of a generic lifetime.
+///
+/// ---
+///
+/// The upcoming Rust feature, [Generic Associated Types], should obviate
+/// the need for this trait.
+///
+/// [Generic Associated Types]: https://www.google.com/search?q=generic+associated+types+rust&oq=generic+associated+types+rust&aqs=chrome..69i57j0l5.3327j0j7&sourceid=chrome&ie=UTF-8
 pub trait HasRawValue<'c> {
+    /// The Rust type used to hold a not-yet-decoded value that has just been
+    /// received from the database.
+    ///
+    /// For example, **Postgres** and **MySQL** use `&'c [u8]`; however, **SQLite** uses `SqliteValue<'c>`.
     type RawValue;
 }
 
+/// Associate [`Database`] with a [`Cursor`] of a generic lifetime.
+///
+/// ---
+///
+/// The upcoming Rust feature, [Generic Associated Types], should obviate
+/// the need for this trait.
+///
+/// [Generic Associated Types]: https://www.google.com/search?q=generic+associated+types+rust&oq=generic+associated+types+rust&aqs=chrome..69i57j0l5.3327j0j7&sourceid=chrome&ie=UTF-8
 pub trait HasCursor<'c, 'q> {
     type Database: Database;
 
+    /// The concrete `Cursor` implementation for this database.
     type Cursor: Cursor<'c, 'q, Database = Self::Database>;
 }
 
+/// Associate [`Database`] with a [`Row`] of a generic lifetime.
+///
+/// ---
+///
+/// The upcoming Rust feature, [Generic Associated Types], should obviate
+/// the need for this trait.
+///
+/// [Generic Associated Types]: https://www.google.com/search?q=generic+associated+types+rust&oq=generic+associated+types+rust&aqs=chrome..69i57j0l5.3327j0j7&sourceid=chrome&ie=UTF-8
 pub trait HasRow<'c> {
     type Database: Database;
 
+    /// The concrete `Row` implementation for this database.
     type Row: Row<'c, Database = Self::Database>;
 }

sqlx-core/src/mysql/protocol/row.rs

@@ -126,6 +126,7 @@ impl<'c> Row<'c> {
                     | TypeId::LONG_BLOB
                     | TypeId::CHAR
                     | TypeId::TEXT
+                    | TypeId::ENUM
                     | TypeId::VAR_CHAR => {
                         let (len_size, len) = get_lenenc(&buffer[index..]);
 

sqlx-core/src/mysql/protocol/type.rs

@@ -39,6 +39,9 @@ type_id_consts! {
     pub const VAR_CHAR: TypeId = TypeId(253); // or VAR_BINARY
     pub const TEXT: TypeId = TypeId(252); // or BLOB
 
+    // Enum
+    pub const ENUM: TypeId = TypeId(247);
+
     // More Bytes
     pub const TINY_BLOB: TypeId = TypeId(249);
     pub const MEDIUM_BLOB: TypeId = TypeId(250);

sqlx-core/src/mysql/types/mod.rs

@@ -85,6 +85,7 @@ impl TypeInfo for MySqlTypeInfo {
             | TypeId::TINY_BLOB
             | TypeId::MEDIUM_BLOB
             | TypeId::LONG_BLOB
+            | TypeId::ENUM
                 if (self.is_binary == other.is_binary)
                     && match other.id {
                         TypeId::VAR_CHAR
@@ -92,7 +93,8 @@ impl TypeInfo for MySqlTypeInfo {
                         | TypeId::CHAR
                         | TypeId::TINY_BLOB
                         | TypeId::MEDIUM_BLOB
-                        | TypeId::LONG_BLOB => true,
+                        | TypeId::LONG_BLOB
+                        | TypeId::ENUM => true,
 
                         _ => false,
                     } =>

sqlx-core/src/postgres/mod.rs

@@ -21,7 +21,7 @@ mod row;
 mod sasl;
 mod stream;
 mod tls;
-mod types;
+pub mod types;
 
 /// An alias for [`Pool`][crate::Pool], specialized for **Postgres**.
 pub type PgPool = crate::pool::Pool<PgConnection>;

sqlx-core/src/postgres/row.rs

@@ -11,6 +11,7 @@ use crate::row::{ColumnIndex, Row};
 
 /// A value from Postgres. This may be in a BINARY or TEXT format depending
 /// on the data type and if the query was prepared or not.
+#[derive(Debug)]
 pub enum PgValue<'c> {
     Binary(&'c [u8]),
     Text(&'c str),

sqlx-core/src/postgres/types/mod.rs

@@ -11,8 +11,11 @@ mod bool;
 mod bytes;
 mod float;
 mod int;
+mod record;
 mod str;
 
+pub use self::record::{PgRecordDecoder, PgRecordEncoder};
+
 #[cfg(feature = "chrono")]
 mod chrono;
 
@@ -57,6 +60,10 @@ impl PgTypeInfo {
             _ => None,
         }
     }
+
+    pub fn oid(&self) -> u32 {
+        self.id.0
+    }
 }
 
 impl Display for PgTypeInfo {

sqlx-core/src/postgres/types/record.rs

@@ -0,0 +1,309 @@
+use crate::decode::Decode;
+use crate::encode::{Encode, IsNull};
+use crate::io::Buf;
+use crate::postgres::protocol::TypeId;
+use crate::postgres::{PgTypeInfo, PgValue, Postgres};
+use crate::types::Type;
+use byteorder::BigEndian;
+use std::convert::TryInto;
+
+pub struct PgRecordEncoder<'a> {
+    buf: &'a mut Vec<u8>,
+    beg: usize,
+    num: u32,
+}
+
+impl<'a> PgRecordEncoder<'a> {
+    pub fn new(buf: &'a mut Vec<u8>) -> Self {
+        // reserve space for a field count
+        buf.extend_from_slice(&(0_u32).to_be_bytes());
+
+        Self {
+            beg: buf.len(),
+            buf,
+            num: 0,
+        }
+    }
+
+    pub fn finish(&mut self) {
+        // replaces zeros with actual length
+        self.buf[self.beg - 4..self.beg].copy_from_slice(&self.num.to_be_bytes());
+    }
+
+    pub fn encode<T>(&mut self, value: T) -> &mut Self
+    where
+        T: Type<Postgres> + Encode<Postgres>,
+    {
+        // write oid
+        let info = T::type_info();
+        self.buf.extend(&info.oid().to_be_bytes());
+
+        // write zeros for length
+        self.buf.extend(&[0; 4]);
+
+        let start = self.buf.len();
+        if let IsNull::Yes = value.encode_nullable(self.buf) {
+            // replaces zeros with actual length
+            self.buf[start - 4..start].copy_from_slice(&(-1_i32).to_be_bytes());
+        } else {
+            let end = self.buf.len();
+            let size = end - start;
+
+            // replaces zeros with actual length
+            self.buf[start - 4..start].copy_from_slice(&(size as u32).to_be_bytes());
+        }
+
+        // keep track of count
+        self.num += 1;
+
+        self
+    }
+}
+
+pub struct PgRecordDecoder<'de> {
+    value: PgValue<'de>,
+}
+
+impl<'de> PgRecordDecoder<'de> {
+    pub fn new(value: Option<PgValue<'de>>) -> crate::Result<Self> {
+        let mut value: PgValue = value.try_into()?;
+
+        match value {
+            PgValue::Binary(ref mut buf) => {
+                let _expected_len = buf.get_u32::<BigEndian>()?;
+            }
+
+            PgValue::Text(ref mut s) => {
+                // remove outer ( ... )
+                *s = &s[1..(s.len() - 1)];
+            }
+        }
+
+        Ok(Self { value })
+    }
+
+    pub fn decode<T>(&mut self) -> crate::Result<T>
+    where
+        T: Decode<'de, Postgres>,
+    {
+        match self.value {
+            PgValue::Binary(ref mut buf) => {
+                // TODO: We should fail if this type is not _compatible_; but
+                //       I want to make sure we handle this _and_ the outer level
+                //       type mismatch errors at the same time
+                let _oid = buf.get_u32::<BigEndian>()?;
+                let len = buf.get_i32::<BigEndian>()? as isize;
+
+                let value = if len < 0 {
+                    T::decode(None)?
+                } else {
+                    let value_buf = &buf[..(len as usize)];
+                    *buf = &buf[(len as usize)..];
+
+                    T::decode(Some(PgValue::Binary(value_buf)))?
+                };
+
+                Ok(value)
+            }
+
+            PgValue::Text(ref mut s) => {
+                let mut in_quotes = false;
+                let mut in_escape = false;
+                let mut is_quoted = false;
+                let mut prev_ch = '\0';
+                let mut eos = false;
+                let mut prev_index = 0;
+                let mut value = String::new();
+
+                let index = 'outer: loop {
+                    let mut iter = s.char_indices();
+                    while let Some((index, ch)) = iter.next() {
+                        match ch {
+                            ',' if !in_quotes => {
+                                break 'outer Some(prev_index);
+                            }
+
+                            ',' if prev_ch == '\0' => {
+                                break 'outer None;
+                            }
+
+                            '"' if prev_ch == '"' && index != 1 => {
+                                // Quotes are escaped with another quote
+                                in_quotes = false;
+                                value.push('"');
+                            }
+
+                            '"' if in_quotes => {
+                                in_quotes = false;
+                            }
+
+                            '\'' if in_escape => {
+                                in_escape = false;
+                                value.push('\'');
+                            }
+
+                            '"' if in_escape => {
+                                in_escape = false;
+                                value.push('"');
+                            }
+
+                            '\\' if in_escape => {
+                                in_escape = false;
+                                value.push('\\');
+                            }
+
+                            '\\' => {
+                                in_escape = true;
+                            }
+
+                            '"' => {
+                                is_quoted = true;
+                                in_quotes = true;
+                            }
+
+                            ch => {
+                                value.push(ch);
+                            }
+                        }
+
+                        prev_index = index;
+                        prev_ch = ch;
+                    }
+
+                    eos = true;
+
+                    break 'outer if prev_ch == '\0' {
+                        // NULL values have zero characters
+                        // Empty strings are ""
+                        None
+                    } else {
+                        Some(prev_index)
+                    };
+                };
+
+                let value = index.map(|index| {
+                    let mut s = &s[..=index];
+
+                    if is_quoted {
+                        s = &s[1..s.len() - 1];
+                    }
+
+                    PgValue::Text(s)
+                });
+
+                let value = T::decode(value)?;
+
+                if !eos {
+                    *s = &s[index.unwrap_or(0) + 2..];
+                } else {
+                    *s = "";
+                }
+
+                Ok(value)
+            }
+        }
+    }
+}
+
+macro_rules! impl_pg_record_for_tuple {
+    ($( $idx:ident : $T:ident ),+) => {
+        impl<$($T,)+> Type<Postgres> for ($($T,)+) {
+            #[inline]
+            fn type_info() -> PgTypeInfo {
+                PgTypeInfo {
+                    id: TypeId(2249),
+                    name: Some("RECORD".into()),
+                }
+            }
+        }
+
+        impl<'de, $($T,)+> Decode<'de, Postgres> for ($($T,)+)
+        where
+            $($T: crate::types::Type<Postgres>,)+
+            $($T: crate::decode::Decode<'de, Postgres>,)+
+        {
+            fn decode(value: Option<PgValue<'de>>) -> crate::Result<Self> {
+                let mut decoder = PgRecordDecoder::new(value)?;
+
+                $(let $idx: $T = decoder.decode()?;)+
+
+                Ok(($($idx,)+))
+            }
+        }
+    };
+}
+
+impl_pg_record_for_tuple!(_1: T1);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2, _3: T3);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2, _3: T3, _4: T4);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2, _3: T3, _4: T4, _5: T5);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2, _3: T3, _4: T4, _5: T5, _6: T6);
+
+impl_pg_record_for_tuple!(_1: T1, _2: T2, _3: T3, _4: T4, _5: T5, _6: T6, _7: T7);
+
+impl_pg_record_for_tuple!(
+    _1: T1,
+    _2: T2,
+    _3: T3,
+    _4: T4,
+    _5: T5,
+    _6: T6,
+    _7: T7,
+    _8: T8
+);
+
+impl_pg_record_for_tuple!(
+    _1: T1,
+    _2: T2,
+    _3: T3,
+    _4: T4,
+    _5: T5,
+    _6: T6,
+    _7: T7,
+    _8: T8,
+    _9: T9
+);
+
+#[test]
+fn test_encode_field() {
+    let value = "Foo Bar";
+    let mut raw_encoded = Vec::new();
+    <&str as Encode<Postgres>>::encode(&value, &mut raw_encoded);
+    let mut field_encoded = Vec::new();
+
+    let mut encoder = PgRecordEncoder::new(&mut field_encoded);
+    encoder.encode(&value);
+
+    // check oid
+    let oid = <&str as Type<Postgres>>::type_info().oid();
+    let field_encoded_oid = u32::from_be_bytes(field_encoded[4..8].try_into().unwrap());
+    assert_eq!(oid, field_encoded_oid);
+
+    // check length
+    let field_encoded_length = u32::from_be_bytes(field_encoded[8..12].try_into().unwrap());
+    assert_eq!(raw_encoded.len(), field_encoded_length as usize);
+
+    // check data
+    assert_eq!(raw_encoded, &field_encoded[12..]);
+}
+
+#[test]
+fn test_decode_field() {
+    let value = "Foo Bar".to_string();
+
+    let mut buf = Vec::new();
+    let mut encoder = PgRecordEncoder::new(&mut buf);
+    encoder.encode(&value);
+
+    let mut buf = buf.as_slice();
+    let mut decoder = PgRecordDecoder::new(Some(PgValue::Binary(buf))).unwrap();
+
+    let value_decoded: String = decoder.decode().unwrap();
+    assert_eq!(value_decoded, value);
+}

sqlx-core/src/sqlite/arguments.rs

@@ -9,7 +9,7 @@ use libsqlite3_sys::{
 };
 
 use crate::arguments::Arguments;
-use crate::encode::Encode;
+use crate::encode::{Encode, IsNull};
 use crate::sqlite::statement::Statement;
 use crate::sqlite::Sqlite;
 use crate::sqlite::SqliteError;
@@ -63,7 +63,9 @@ impl Arguments for SqliteArguments {
     where
         T: Encode<Self::Database> + Type<Self::Database>,
     {
-        value.encode(&mut self.values);
+        if let IsNull::Yes = value.encode_nullable(&mut self.values) {
+            self.values.push(SqliteArgumentValue::Null);
+        }
     }
 }
 

sqlx-macros/src/derives.rs

@@ -1,108 +0,0 @@
-use quote::quote;
-use syn::{parse_quote, Data, DataStruct, DeriveInput, Fields, FieldsUnnamed};
-
-pub(crate) fn expand_derive_encode(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
-    match &input.data {
-        Data::Struct(DataStruct {
-            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
-            ..
-        }) if unnamed.len() == 1 => {
-            let ident = &input.ident;
-            let ty = &unnamed.first().unwrap().ty;
-
-            // extract type generics
-            let generics = &input.generics;
-            let (_, ty_generics, _) = generics.split_for_impl();
-
-            // add db type for impl generics & where clause
-            let mut generics = generics.clone();
-            generics.params.insert(0, parse_quote!(DB: sqlx::Database));
-            generics
-                .make_where_clause()
-                .predicates
-                .push(parse_quote!(#ty: sqlx::encode::Encode<DB>));
-            let (impl_generics, _, where_clause) = generics.split_for_impl();
-
-            Ok(quote!(
-                impl #impl_generics sqlx::encode::Encode<DB> for #ident #ty_generics #where_clause {
-                    fn encode(&self, buf: &mut <DB as sqlx::Database>::RawBuffer) {
-                        sqlx::encode::Encode::encode(&self.0, buf)
-                    }
-                    fn encode_nullable(&self, buf: &mut <DB as sqlx::Database>::RawBuffer) -> sqlx::encode::IsNull {
-                        sqlx::encode::Encode::encode_nullable(&self.0, buf)
-                    }
-                    fn size_hint(&self) -> usize {
-                        sqlx::encode::Encode::size_hint(&self.0)
-                    }
-                }
-            ))
-        }
-        _ => Err(syn::Error::new_spanned(
-            input,
-            "expected a tuple struct with a single field",
-        )),
-    }
-}
-
-pub(crate) fn expand_derive_decode(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
-    match &input.data {
-        Data::Struct(DataStruct {
-            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
-            ..
-        }) if unnamed.len() == 1 => {
-            let ident = &input.ident;
-            let ty = &unnamed.first().unwrap().ty;
-
-            // extract type generics
-            let generics = &input.generics;
-            let (_, ty_generics, _) = generics.split_for_impl();
-
-            let mut impls = Vec::new();
-
-            if cfg!(feature = "postgres") {
-                let mut generics = generics.clone();
-                generics.params.insert(0, parse_quote!('de));
-                generics
-                    .make_where_clause()
-                    .predicates
-                    .push(parse_quote!(#ty: sqlx::decode::Decode<'de, sqlx::Postgres>));
-
-                let (impl_generics, _, where_clause) = generics.split_for_impl();
-
-                impls.push(quote!(
-                    impl #impl_generics sqlx::decode::Decode<'de, sqlx::Postgres> for #ident #ty_generics #where_clause {
-                        fn decode(value: <sqlx::Postgres as sqlx::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
-                            <#ty as sqlx::decode::Decode<'de, sqlx::Postgres>>::decode(value).map(Self)
-                        }
-                    }
-                ));
-            }
-
-            if cfg!(feature = "mysql") {
-                let mut generics = generics.clone();
-                generics.params.insert(0, parse_quote!('de));
-                generics
-                    .make_where_clause()
-                    .predicates
-                    .push(parse_quote!(#ty: sqlx::decode::Decode<'de, sqlx::MySql>));
-
-                let (impl_generics, _, where_clause) = generics.split_for_impl();
-
-                impls.push(quote!(
-                    impl #impl_generics sqlx::decode::Decode<'de, sqlx::MySql> for #ident #ty_generics #where_clause {
-                        fn decode(value: <sqlx::MySql as sqlx::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
-                            <#ty as sqlx::decode::Decode<'de, sqlx::MySql>>::decode(value).map(Self)
-                        }
-                    }
-                ));
-            }
-
-            // panic!("{}", q)
-            Ok(quote!(#(#impls)*))
-        }
-        _ => Err(syn::Error::new_spanned(
-            input,
-            "expected a tuple struct with a single field",
-        )),
-    }
-}

sqlx-macros/src/derives/attributes.rs

@@ -0,0 +1,291 @@
+use proc_macro2::Ident;
+use syn::punctuated::Punctuated;
+use syn::token::Comma;
+use syn::{Attribute, DeriveInput, Field, Lit, Meta, MetaNameValue, NestedMeta, Variant};
+
+macro_rules! assert_attribute {
+    ($e:expr, $err:expr, $input:expr) => {
+        if !$e {
+            return Err(syn::Error::new_spanned($input, $err));
+        }
+    };
+}
+
+macro_rules! fail {
+    ($t:expr, $m:expr) => {
+        return Err(syn::Error::new_spanned($t, $m));
+    };
+}
+
+macro_rules! try_set {
+    ($i:ident, $v:expr, $t:expr) => {
+        match $i {
+            None => $i = Some($v),
+            Some(_) => fail!($t, "duplicate attribute"),
+        }
+    };
+}
+
+#[derive(Copy, Clone)]
+pub enum RenameAll {
+    LowerCase,
+}
+
+pub struct SqlxContainerAttributes {
+    pub transparent: bool,
+    pub postgres_oid: Option<u32>,
+    pub rename_all: Option<RenameAll>,
+    pub repr: Option<Ident>,
+}
+
+pub struct SqlxChildAttributes {
+    pub rename: Option<String>,
+}
+
+pub fn parse_container_attributes(input: &[Attribute]) -> syn::Result<SqlxContainerAttributes> {
+    let mut transparent = None;
+    let mut postgres_oid = None;
+    let mut repr = None;
+    let mut rename_all = None;
+
+    for attr in input {
+        let meta = attr
+            .parse_meta()
+            .map_err(|e| syn::Error::new_spanned(attr, e))?;
+        match meta {
+            Meta::List(list) if list.path.is_ident("sqlx") => {
+                for value in list.nested.iter() {
+                    match value {
+                        NestedMeta::Meta(meta) => match meta {
+                            Meta::Path(p) if p.is_ident("transparent") => {
+                                try_set!(transparent, true, value)
+                            }
+
+                            Meta::NameValue(MetaNameValue {
+                                path,
+                                lit: Lit::Str(val),
+                                ..
+                            }) if path.is_ident("rename_all") => {
+                                let val = match &*val.value() {
+                                    "lowercase" => RenameAll::LowerCase,
+
+                                    _ => fail!(meta, "unexpected value for rename_all"),
+                                };
+
+                                try_set!(rename_all, val, value)
+                            }
+
+                            Meta::List(list) if list.path.is_ident("postgres") => {
+                                for value in list.nested.iter() {
+                                    match value {
+                                        NestedMeta::Meta(Meta::NameValue(MetaNameValue {
+                                            path,
+                                            lit: Lit::Int(val),
+                                            ..
+                                        })) if path.is_ident("oid") => {
+                                            try_set!(postgres_oid, val.base10_parse()?, value);
+                                        }
+                                        u => fail!(u, "unexpected value"),
+                                    }
+                                }
+                            }
+
+                            u => fail!(u, "unexpected attribute"),
+                        },
+                        u => fail!(u, "unexpected attribute"),
+                    }
+                }
+            }
+            Meta::List(list) if list.path.is_ident("repr") => {
+                if list.nested.len() != 1 {
+                    fail!(&list.nested, "expected one value")
+                }
+                match list.nested.first().unwrap() {
+                    NestedMeta::Meta(Meta::Path(p)) if p.get_ident().is_some() => {
+                        try_set!(repr, p.get_ident().unwrap().clone(), list);
+                    }
+                    u => fail!(u, "unexpected value"),
+                }
+            }
+            _ => {}
+        }
+    }
+
+    Ok(SqlxContainerAttributes {
+        transparent: transparent.unwrap_or(false),
+        postgres_oid,
+        repr,
+        rename_all,
+    })
+}
+
+pub fn parse_child_attributes(input: &[Attribute]) -> syn::Result<SqlxChildAttributes> {
+    let mut rename = None;
+
+    for attr in input {
+        let meta = attr
+            .parse_meta()
+            .map_err(|e| syn::Error::new_spanned(attr, e))?;
+
+        match meta {
+            Meta::List(list) if list.path.is_ident("sqlx") => {
+                for value in list.nested.iter() {
+                    match value {
+                        NestedMeta::Meta(meta) => match meta {
+                            Meta::NameValue(MetaNameValue {
+                                path,
+                                lit: Lit::Str(val),
+                                ..
+                            }) if path.is_ident("rename") => try_set!(rename, val.value(), value),
+
+                            u => fail!(u, "unexpected attribute"),
+                        },
+                        u => fail!(u, "unexpected attribute"),
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+
+    Ok(SqlxChildAttributes { rename })
+}
+
+pub fn check_transparent_attributes(input: &DeriveInput, field: &Field) -> syn::Result<()> {
+    let attributes = parse_container_attributes(&input.attrs)?;
+
+    assert_attribute!(
+        attributes.transparent,
+        "expected #[sqlx(transparent)]",
+        input
+    );
+
+    #[cfg(feature = "postgres")]
+    assert_attribute!(
+        attributes.postgres_oid.is_none(),
+        "unexpected #[sqlx(postgres(oid = ..))]",
+        input
+    );
+
+    assert_attribute!(
+        attributes.rename_all.is_none(),
+        "unexpected #[sqlx(rename_all = ..)]",
+        field
+    );
+
+    assert_attribute!(attributes.repr.is_none(), "unexpected #[repr(..)]", input);
+
+    let attributes = parse_child_attributes(&field.attrs)?;
+
+    assert_attribute!(
+        attributes.rename.is_none(),
+        "unexpected #[sqlx(rename = ..)]",
+        field
+    );
+
+    Ok(())
+}
+
+pub fn check_enum_attributes<'a>(input: &'a DeriveInput) -> syn::Result<SqlxContainerAttributes> {
+    let attributes = parse_container_attributes(&input.attrs)?;
+
+    assert_attribute!(
+        !attributes.transparent,
+        "unexpected #[sqlx(transparent)]",
+        input
+    );
+
+    Ok(attributes)
+}
+
+pub fn check_weak_enum_attributes(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<SqlxContainerAttributes> {
+    let attributes = check_enum_attributes(input)?;
+
+    #[cfg(feature = "postgres")]
+    assert_attribute!(
+        attributes.postgres_oid.is_none(),
+        "unexpected #[sqlx(postgres(oid = ..))]",
+        input
+    );
+
+    assert_attribute!(attributes.repr.is_some(), "expected #[repr(..)]", input);
+
+    assert_attribute!(
+        attributes.rename_all.is_none(),
+        "unexpected #[sqlx(c = ..)]",
+        input
+    );
+
+    for variant in variants {
+        let attributes = parse_child_attributes(&variant.attrs)?;
+
+        assert_attribute!(
+            attributes.rename.is_none(),
+            "unexpected #[sqlx(rename = ..)]",
+            variant
+        );
+    }
+
+    Ok(attributes)
+}
+
+pub fn check_strong_enum_attributes(
+    input: &DeriveInput,
+    _variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<SqlxContainerAttributes> {
+    let attributes = check_enum_attributes(input)?;
+
+    #[cfg(feature = "postgres")]
+    assert_attribute!(
+        attributes.postgres_oid.is_some(),
+        "expected #[sqlx(postgres(oid = ..))]",
+        input
+    );
+
+    assert_attribute!(attributes.repr.is_none(), "unexpected #[repr(..)]", input);
+
+    Ok(attributes)
+}
+
+pub fn check_struct_attributes<'a>(
+    input: &'a DeriveInput,
+    fields: &Punctuated<Field, Comma>,
+) -> syn::Result<SqlxContainerAttributes> {
+    let attributes = parse_container_attributes(&input.attrs)?;
+
+    assert_attribute!(
+        !attributes.transparent,
+        "unexpected #[sqlx(transparent)]",
+        input
+    );
+
+    #[cfg(feature = "postgres")]
+    assert_attribute!(
+        attributes.postgres_oid.is_some(),
+        "expected #[sqlx(postgres(oid = ..))]",
+        input
+    );
+
+    assert_attribute!(
+        attributes.rename_all.is_none(),
+        "unexpected #[sqlx(rename_all = ..)]",
+        input
+    );
+
+    assert_attribute!(attributes.repr.is_none(), "unexpected #[repr(..)]", input);
+
+    for field in fields {
+        let attributes = parse_child_attributes(&field.attrs)?;
+
+        assert_attribute!(
+            attributes.rename.is_none(),
+            "unexpected #[sqlx(rename = ..)]",
+            field
+        );
+    }
+
+    Ok(attributes)
+}

sqlx-macros/src/derives/decode.rs

@@ -0,0 +1,212 @@
+use super::attributes::{
+    check_strong_enum_attributes, check_struct_attributes, check_transparent_attributes,
+    check_weak_enum_attributes, parse_child_attributes, parse_container_attributes,
+};
+use super::rename_all;
+use quote::quote;
+use syn::punctuated::Punctuated;
+use syn::token::Comma;
+use syn::{
+    parse_quote, Arm, Data, DataEnum, DataStruct, DeriveInput, Field, Fields, FieldsNamed,
+    FieldsUnnamed, Stmt, Variant,
+};
+
+pub fn expand_derive_decode(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
+    let attrs = parse_container_attributes(&input.attrs)?;
+    match &input.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
+            ..
+        }) if unnamed.len() == 1 => {
+            expand_derive_decode_transparent(input, unnamed.first().unwrap())
+        }
+        Data::Enum(DataEnum { variants, .. }) => match attrs.repr {
+            Some(_) => expand_derive_decode_weak_enum(input, variants),
+            None => expand_derive_decode_strong_enum(input, variants),
+        },
+        Data::Struct(DataStruct {
+            fields: Fields::Named(FieldsNamed { named, .. }),
+            ..
+        }) => expand_derive_decode_struct(input, named),
+        Data::Union(_) => Err(syn::Error::new_spanned(input, "unions are not supported")),
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(..),
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "structs with zero or more than one unnamed field are not supported",
+        )),
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "unit structs are not supported",
+        )),
+    }
+}
+
+fn expand_derive_decode_transparent(
+    input: &DeriveInput,
+    field: &Field,
+) -> syn::Result<proc_macro2::TokenStream> {
+    check_transparent_attributes(input, field)?;
+
+    let ident = &input.ident;
+    let ty = &field.ty;
+
+    // extract type generics
+    let generics = &input.generics;
+    let (_, ty_generics, _) = generics.split_for_impl();
+
+    // add db type for impl generics & where clause
+    let mut generics = generics.clone();
+    generics.params.insert(0, parse_quote!(DB: sqlx::Database));
+    generics.params.insert(0, parse_quote!('de));
+    generics
+        .make_where_clause()
+        .predicates
+        .push(parse_quote!(#ty: sqlx::decode::Decode<'de, DB>));
+    let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+    let tts = quote!(
+        impl #impl_generics sqlx::decode::Decode<'de, DB> for #ident #ty_generics #where_clause {
+            fn decode(value: <DB as sqlx::database::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
+                <#ty as sqlx::decode::Decode<'de, DB>>::decode(value).map(Self)
+            }
+        }
+    );
+
+    Ok(tts)
+}
+
+fn expand_derive_decode_weak_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let attr = check_weak_enum_attributes(input, &variants)?;
+    let repr = attr.repr.unwrap();
+
+    let ident = &input.ident;
+    let ident_s = ident.to_string();
+
+    let arms = variants
+        .iter()
+        .map(|v| {
+            let id = &v.ident;
+            parse_quote!(_ if (#ident :: #id as #repr) == value => Ok(#ident :: #id),)
+        })
+        .collect::<Vec<Arm>>();
+
+    Ok(quote!(
+        impl<'de, DB: sqlx::Database> sqlx::decode::Decode<'de, DB> for #ident where #repr: sqlx::decode::Decode<'de, DB> {
+            fn decode(value: <DB as sqlx::database::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
+                let value = <#repr as sqlx::decode::Decode<'de, DB>>::decode(value)?;
+
+                match value {
+                    #(#arms)*
+
+                    _ => Err(sqlx::Error::Decode(format!("invalid value {:?} for enum {}", value, #ident_s).into()))
+                }
+            }
+        }
+    ))
+}
+
+fn expand_derive_decode_strong_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let cattr = check_strong_enum_attributes(input, &variants)?;
+
+    let ident = &input.ident;
+    let ident_s = ident.to_string();
+
+    let value_arms = variants.iter().map(|v| -> Arm {
+        let id = &v.ident;
+        let attributes = parse_child_attributes(&v.attrs).unwrap();
+
+        if let Some(rename) = attributes.rename {
+            parse_quote!(#rename => Ok(#ident :: #id),)
+        } else if let Some(pattern) = cattr.rename_all {
+            let name = rename_all(&*id.to_string(), pattern);
+
+            parse_quote!(#name => Ok(#ident :: #id),)
+        } else {
+            let name = id.to_string();
+            parse_quote!(#name => Ok(#ident :: #id),)
+        }
+    });
+
+    Ok(quote!(
+        impl<'de, DB: sqlx::Database> sqlx::decode::Decode<'de, DB> for #ident where &'de str: sqlx::decode::Decode<'de, DB> {
+            fn decode(value: <DB as sqlx::database::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
+                let value = <&'de str as sqlx::decode::Decode<'de, DB>>::decode(value)?;
+                match value {
+                    #(#value_arms)*
+
+                    _ => Err(sqlx::Error::Decode(format!("invalid value {:?} for enum {}", value, #ident_s).into()))
+                }
+            }
+        }
+    ))
+}
+
+fn expand_derive_decode_struct(
+    input: &DeriveInput,
+    fields: &Punctuated<Field, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    check_struct_attributes(input, fields)?;
+
+    let mut tts = proc_macro2::TokenStream::new();
+
+    if cfg!(feature = "postgres") {
+        let ident = &input.ident;
+
+        // extract type generics
+        let generics = &input.generics;
+        let (_, ty_generics, _) = generics.split_for_impl();
+
+        // add db type for impl generics & where clause
+        let mut generics = generics.clone();
+        generics.params.insert(0, parse_quote!('de));
+
+        let predicates = &mut generics.make_where_clause().predicates;
+
+        for field in fields {
+            let ty = &field.ty;
+
+            predicates.push(parse_quote!(#ty: sqlx::decode::Decode<'de, sqlx::Postgres>));
+            predicates.push(parse_quote!(#ty: sqlx::types::Type<sqlx::Postgres>));
+        }
+
+        let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+        let reads = fields.iter().map(|field| -> Stmt {
+            let id = &field.ident;
+            let ty = &field.ty;
+
+            parse_quote!(
+                let #id = decoder.decode::<#ty>()?;
+            )
+        });
+
+        let names = fields.iter().map(|field| &field.ident);
+
+        tts.extend(quote!(
+            impl #impl_generics sqlx::decode::Decode<'de, sqlx::Postgres> for #ident #ty_generics #where_clause {
+                fn decode(value: <sqlx::Postgres as sqlx::database::HasRawValue<'de>>::RawValue) -> sqlx::Result<Self> {
+                    let mut decoder = sqlx::postgres::types::PgRecordDecoder::new(value)?;
+
+                    #(#reads)*
+
+                    Ok(#ident {
+                        #(#names),*
+                    })
+                }
+            }
+        ));
+    }
+
+    Ok(tts)
+}

sqlx-macros/src/derives/encode.rs

@@ -0,0 +1,223 @@
+use super::attributes::{
+    check_strong_enum_attributes, check_struct_attributes, check_transparent_attributes,
+    check_weak_enum_attributes, parse_child_attributes, parse_container_attributes,
+};
+use super::rename_all;
+use quote::quote;
+use syn::punctuated::Punctuated;
+use syn::token::Comma;
+use syn::{
+    parse_quote, Data, DataEnum, DataStruct, DeriveInput, Expr, Field, Fields, FieldsNamed,
+    FieldsUnnamed, Stmt, Variant,
+};
+
+pub fn expand_derive_encode(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
+    let args = parse_container_attributes(&input.attrs)?;
+
+    match &input.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
+            ..
+        }) if unnamed.len() == 1 => {
+            expand_derive_encode_transparent(&input, unnamed.first().unwrap())
+        }
+        Data::Enum(DataEnum { variants, .. }) => match args.repr {
+            Some(_) => expand_derive_encode_weak_enum(input, variants),
+            None => expand_derive_encode_strong_enum(input, variants),
+        },
+        Data::Struct(DataStruct {
+            fields: Fields::Named(FieldsNamed { named, .. }),
+            ..
+        }) => expand_derive_encode_struct(input, named),
+        Data::Union(_) => Err(syn::Error::new_spanned(input, "unions are not supported")),
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(..),
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "structs with zero or more than one unnamed field are not supported",
+        )),
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "unit structs are not supported",
+        )),
+    }
+}
+
+fn expand_derive_encode_transparent(
+    input: &DeriveInput,
+    field: &Field,
+) -> syn::Result<proc_macro2::TokenStream> {
+    check_transparent_attributes(input, field)?;
+
+    let ident = &input.ident;
+    let ty = &field.ty;
+
+    // extract type generics
+    let generics = &input.generics;
+    let (_, ty_generics, _) = generics.split_for_impl();
+
+    // add db type for impl generics & where clause
+    let mut generics = generics.clone();
+    generics.params.insert(0, parse_quote!(DB: sqlx::Database));
+    generics
+        .make_where_clause()
+        .predicates
+        .push(parse_quote!(#ty: sqlx::encode::Encode<DB>));
+    let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+    Ok(quote!(
+        impl #impl_generics sqlx::encode::Encode<DB> for #ident #ty_generics #where_clause {
+            fn encode(&self, buf: &mut DB::RawBuffer) {
+                sqlx::encode::Encode::encode(&self.0, buf)
+            }
+            fn encode_nullable(&self, buf: &mut DB::RawBuffer) -> sqlx::encode::IsNull {
+                sqlx::encode::Encode::encode_nullable(&self.0, buf)
+            }
+            fn size_hint(&self) -> usize {
+                sqlx::encode::Encode::size_hint(&self.0)
+            }
+        }
+    ))
+}
+
+fn expand_derive_encode_weak_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let attr = check_weak_enum_attributes(input, &variants)?;
+    let repr = attr.repr.unwrap();
+
+    let ident = &input.ident;
+
+    Ok(quote!(
+        impl<DB: sqlx::Database> sqlx::encode::Encode<DB> for #ident where #repr: sqlx::encode::Encode<DB> {
+            fn encode(&self, buf: &mut DB::RawBuffer) {
+                sqlx::encode::Encode::encode(&(*self as #repr), buf)
+            }
+
+            fn encode_nullable(&self, buf: &mut DB::RawBuffer) -> sqlx::encode::IsNull {
+                sqlx::encode::Encode::encode_nullable(&(*self as #repr), buf)
+            }
+
+            fn size_hint(&self) -> usize {
+                sqlx::encode::Encode::size_hint(&(*self as #repr))
+            }
+        }
+    ))
+}
+
+fn expand_derive_encode_strong_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let cattr = check_strong_enum_attributes(input, &variants)?;
+
+    let ident = &input.ident;
+
+    let mut value_arms = Vec::new();
+    for v in variants {
+        let id = &v.ident;
+        let attributes = parse_child_attributes(&v.attrs)?;
+
+        if let Some(rename) = attributes.rename {
+            value_arms.push(quote!(#ident :: #id => #rename,));
+        } else if let Some(pattern) = cattr.rename_all {
+            let name = rename_all(&*id.to_string(), pattern);
+
+            value_arms.push(quote!(#ident :: #id => #name,));
+        } else {
+            let name = id.to_string();
+            value_arms.push(quote!(#ident :: #id => #name,));
+        }
+    }
+
+    Ok(quote!(
+        impl<DB: sqlx::Database> sqlx::encode::Encode<DB> for #ident where str: sqlx::encode::Encode<DB> {
+            fn encode(&self, buf: &mut DB::RawBuffer) {
+                let val = match self {
+                    #(#value_arms)*
+                };
+                <str as sqlx::encode::Encode<DB>>::encode(val, buf)
+            }
+
+            fn size_hint(&self) -> usize {
+                let val = match self {
+                    #(#value_arms)*
+                };
+                <str as sqlx::encode::Encode<DB>>::size_hint(val)
+            }
+        }
+    ))
+}
+
+fn expand_derive_encode_struct(
+    input: &DeriveInput,
+    fields: &Punctuated<Field, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    check_struct_attributes(input, &fields)?;
+
+    let mut tts = proc_macro2::TokenStream::new();
+
+    if cfg!(feature = "postgres") {
+        let ident = &input.ident;
+        let column_count = fields.len();
+
+        // extract type generics
+        let generics = &input.generics;
+        let (_, ty_generics, _) = generics.split_for_impl();
+
+        // add db type for impl generics & where clause
+        let mut generics = generics.clone();
+        let predicates = &mut generics.make_where_clause().predicates;
+
+        for field in fields {
+            let ty = &field.ty;
+
+            predicates.push(parse_quote!(#ty: sqlx::encode::Encode<sqlx::Postgres>));
+            predicates.push(parse_quote!(#ty: sqlx::types::Type<sqlx::Postgres>));
+        }
+
+        let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+        let writes = fields.iter().map(|field| -> Stmt {
+            let id = &field.ident;
+
+            parse_quote!(
+                // sqlx::postgres::encode_struct_field(buf, &self. #id);
+                encoder.encode(&self. #id);
+            )
+        });
+
+        let sizes = fields.iter().map(|field| -> Expr {
+            let id = &field.ident;
+            let ty = &field.ty;
+
+            parse_quote!(
+                <#ty as sqlx::encode::Encode<sqlx::Postgres>>::size_hint(&self. #id)
+            )
+        });
+
+        tts.extend(quote!(
+            impl #impl_generics sqlx::encode::Encode<sqlx::Postgres> for #ident #ty_generics #where_clause {
+                fn encode(&self, buf: &mut std::vec::Vec<u8>) {
+                    let mut encoder = sqlx::postgres::types::PgRecordEncoder::new(buf);
+
+                    #(#writes)*
+
+                    encoder.finish();
+                }
+
+                fn size_hint(&self) -> usize {
+                    #column_count * (4 + 4) // oid (int) and length (int) for each column
+                        + #(#sizes)+* // sum of the size hints for each column
+                }
+            }
+        ));
+    }
+
+    Ok(tts)
+}

sqlx-macros/src/derives/mod.rs

@@ -0,0 +1,32 @@
+mod attributes;
+mod decode;
+mod encode;
+mod r#type;
+
+pub(crate) use decode::expand_derive_decode;
+pub(crate) use encode::expand_derive_encode;
+pub(crate) use r#type::expand_derive_type;
+
+use self::attributes::RenameAll;
+use std::iter::FromIterator;
+use syn::DeriveInput;
+
+pub(crate) fn expand_derive_type_encode_decode(
+    input: &DeriveInput,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let encode_tts = expand_derive_encode(input)?;
+    let decode_tts = expand_derive_decode(input)?;
+    let type_tts = expand_derive_type(input)?;
+
+    let combined = proc_macro2::TokenStream::from_iter(
+        encode_tts.into_iter().chain(decode_tts).chain(type_tts),
+    );
+
+    Ok(combined)
+}
+
+pub(crate) fn rename_all(s: &str, pattern: RenameAll) -> String {
+    match pattern {
+        RenameAll::LowerCase => s.to_lowercase(),
+    }
+}

sqlx-macros/src/derives/type.rs

@@ -0,0 +1,156 @@
+use super::attributes::{
+    check_strong_enum_attributes, check_struct_attributes, check_transparent_attributes,
+    check_weak_enum_attributes, parse_container_attributes,
+};
+use quote::quote;
+use syn::punctuated::Punctuated;
+use syn::token::Comma;
+use syn::{
+    parse_quote, Data, DataEnum, DataStruct, DeriveInput, Field, Fields, FieldsNamed,
+    FieldsUnnamed, Variant,
+};
+
+pub fn expand_derive_type(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
+    let attrs = parse_container_attributes(&input.attrs)?;
+    match &input.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
+            ..
+        }) if unnamed.len() == 1 => {
+            expand_derive_has_sql_type_transparent(input, unnamed.first().unwrap())
+        }
+        Data::Enum(DataEnum { variants, .. }) => match attrs.repr {
+            Some(_) => expand_derive_has_sql_type_weak_enum(input, variants),
+            None => expand_derive_has_sql_type_strong_enum(input, variants),
+        },
+        Data::Struct(DataStruct {
+            fields: Fields::Named(FieldsNamed { named, .. }),
+            ..
+        }) => expand_derive_has_sql_type_struct(input, named),
+        Data::Union(_) => Err(syn::Error::new_spanned(input, "unions are not supported")),
+        Data::Struct(DataStruct {
+            fields: Fields::Unnamed(..),
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "structs with zero or more than one unnamed field are not supported",
+        )),
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => Err(syn::Error::new_spanned(
+            input,
+            "unit structs are not supported",
+        )),
+    }
+}
+
+fn expand_derive_has_sql_type_transparent(
+    input: &DeriveInput,
+    field: &Field,
+) -> syn::Result<proc_macro2::TokenStream> {
+    check_transparent_attributes(input, field)?;
+
+    let ident = &input.ident;
+    let ty = &field.ty;
+
+    // extract type generics
+    let generics = &input.generics;
+    let (_, ty_generics, _) = generics.split_for_impl();
+
+    // add db type for clause
+    let mut generics = generics.clone();
+    generics.params.insert(0, parse_quote!(DB: sqlx::Database));
+    generics
+        .make_where_clause()
+        .predicates
+        .push(parse_quote!(#ty: sqlx::types::Type<DB>));
+
+    let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+    Ok(quote!(
+        impl #impl_generics sqlx::types::Type< DB > for #ident #ty_generics #where_clause {
+            fn type_info() -> DB::TypeInfo {
+                <#ty as sqlx::Type<DB>>::type_info()
+            }
+        }
+    ))
+}
+
+fn expand_derive_has_sql_type_weak_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let attr = check_weak_enum_attributes(input, variants)?;
+    let repr = attr.repr.unwrap();
+    let ident = &input.ident;
+
+    Ok(quote!(
+        impl<DB: sqlx::Database> sqlx::Type<DB> for #ident
+        where
+            #repr: sqlx::Type<DB>,
+        {
+            fn type_info() -> DB::TypeInfo {
+                <#repr as sqlx::Type<DB>>::type_info()
+            }
+        }
+    ))
+}
+
+fn expand_derive_has_sql_type_strong_enum(
+    input: &DeriveInput,
+    variants: &Punctuated<Variant, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let attributes = check_strong_enum_attributes(input, variants)?;
+
+    let ident = &input.ident;
+    let mut tts = proc_macro2::TokenStream::new();
+
+    if cfg!(feature = "mysql") {
+        tts.extend(quote!(
+            impl sqlx::Type< sqlx::MySql > for #ident {
+                fn type_info() -> sqlx::mysql::MySqlTypeInfo {
+                    // This is really fine, MySQL is loosely typed and
+                    // we don't nede to be specific here
+                    <str as sqlx::Type<sqlx::MySql>>::type_info()
+                }
+            }
+        ));
+    }
+
+    if cfg!(feature = "postgres") {
+        let oid = attributes.postgres_oid.unwrap();
+        tts.extend(quote!(
+            impl sqlx::Type< sqlx::Postgres > for #ident {
+                fn type_info() -> sqlx::postgres::PgTypeInfo {
+                    sqlx::postgres::PgTypeInfo::with_oid(#oid)
+                }
+            }
+        ));
+    }
+
+    Ok(tts)
+}
+
+fn expand_derive_has_sql_type_struct(
+    input: &DeriveInput,
+    fields: &Punctuated<Field, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let attributes = check_struct_attributes(input, fields)?;
+
+    let ident = &input.ident;
+    let mut tts = proc_macro2::TokenStream::new();
+
+    if cfg!(feature = "postgres") {
+        let oid = attributes.postgres_oid.unwrap();
+        tts.extend(quote!(
+            impl sqlx::types::Type< sqlx::Postgres > for #ident {
+                fn type_info() -> sqlx::postgres::PgTypeInfo {
+                    sqlx::postgres::PgTypeInfo::with_oid(#oid)
+                }
+            }
+        ));
+    }
+
+    Ok(tts)
+}

sqlx-macros/src/lib.rs

@@ -151,19 +151,28 @@ pub fn query_file_as(input: TokenStream) -> TokenStream {
     async_macro!(db, input: QueryAsMacroInput => expand_query_file_as(input, db))
 }
 
-#[proc_macro_derive(Encode)]
+#[proc_macro_derive(Encode, attributes(sqlx))]
 pub fn derive_encode(tokenstream: TokenStream) -> TokenStream {
     let input = syn::parse_macro_input!(tokenstream as syn::DeriveInput);
-    match derives::expand_derive_encode(input) {
+    match derives::expand_derive_encode(&input) {
         Ok(ts) => ts.into(),
         Err(e) => e.to_compile_error().into(),
     }
 }
 
-#[proc_macro_derive(Decode)]
+#[proc_macro_derive(Decode, attributes(sqlx))]
 pub fn derive_decode(tokenstream: TokenStream) -> TokenStream {
     let input = syn::parse_macro_input!(tokenstream as syn::DeriveInput);
-    match derives::expand_derive_decode(input) {
+    match derives::expand_derive_decode(&input) {
+        Ok(ts) => ts.into(),
+        Err(e) => e.to_compile_error().into(),
+    }
+}
+
+#[proc_macro_derive(Type, attributes(sqlx))]
+pub fn derive_type(tokenstream: TokenStream) -> TokenStream {
+    let input = syn::parse_macro_input!(tokenstream as syn::DeriveInput);
+    match derives::expand_derive_type_encode_decode(&input) {
         Ok(ts) => ts.into(),
         Err(e) => e.to_compile_error().into(),
     }

src/lib.rs

@@ -40,6 +40,9 @@ pub use sqlx_core::sqlite::{self, Sqlite, SqliteConnection, SqlitePool};
 #[doc(hidden)]
 pub extern crate sqlx_macros;
 
+#[cfg(feature = "macros")]
+pub use sqlx_macros::Type;
+
 #[cfg(feature = "macros")]
 mod macros;
 

src/types.rs

@@ -0,0 +1,6 @@
+//! Traits linking Rust types to SQL types.
+
+pub use sqlx_core::types::*;
+
+#[cfg(feature = "macros")]
+pub use sqlx_macros::HasSqlType;

tests/derives.rs

@@ -1,77 +0,0 @@
-use sqlx::decode::Decode;
-use sqlx::encode::Encode;
-
-#[derive(PartialEq, Debug, Encode, Decode)]
-struct Foo(i32);
-
-#[test]
-#[cfg(feature = "postgres")]
-fn encode_with_postgres() {
-    use sqlx_core::postgres::Postgres;
-
-    let example = Foo(0x1122_3344);
-
-    let mut encoded = Vec::new();
-    let mut encoded_orig = Vec::new();
-
-    Encode::<Postgres>::encode(&example, &mut encoded);
-    Encode::<Postgres>::encode(&example.0, &mut encoded_orig);
-
-    assert_eq!(encoded, encoded_orig);
-}
-
-#[test]
-#[cfg(feature = "mysql")]
-fn encode_with_mysql() {
-    use sqlx_core::mysql::MySql;
-
-    let example = Foo(0x1122_3344);
-
-    let mut encoded = Vec::new();
-    let mut encoded_orig = Vec::new();
-
-    Encode::<MySql>::encode(&example, &mut encoded);
-    Encode::<MySql>::encode(&example.0, &mut encoded_orig);
-
-    assert_eq!(encoded, encoded_orig);
-}
-
-#[test]
-#[cfg(feature = "mysql")]
-fn decode_mysql() {
-    decode_with_db();
-}
-
-#[test]
-#[cfg(feature = "postgres")]
-fn decode_postgres() {
-    decode_with_db();
-}
-
-#[cfg(feature = "postgres")]
-fn decode_with_db()
-where
-    Foo: for<'de> Decode<'de, sqlx::Postgres> + Encode<sqlx::Postgres>,
-{
-    let example = Foo(0x1122_3344);
-
-    let mut encoded = Vec::new();
-    Encode::<sqlx::Postgres>::encode(&example, &mut encoded);
-
-    let decoded = Foo::decode(Some(sqlx::postgres::PgValue::Binary(&encoded))).unwrap();
-    assert_eq!(example, decoded);
-}
-
-#[cfg(feature = "mysql")]
-fn decode_with_db()
-where
-    Foo: for<'de> Decode<'de, sqlx::MySql> + Encode<sqlx::MySql>,
-{
-    let example = Foo(0x1122_3344);
-
-    let mut encoded = Vec::new();
-    Encode::<sqlx::MySql>::encode(&example, &mut encoded);
-
-    let decoded = Foo::decode(Some(sqlx::mysql::MySqlValue::Binary(&encoded))).unwrap();
-    assert_eq!(example, decoded);
-}

tests/mysql-derives.rs

@@ -0,0 +1,43 @@
+use sqlx::MySql;
+use sqlx_test::test_type;
+use std::fmt::Debug;
+
+// Transparent types are rust-side wrappers over DB types
+#[derive(PartialEq, Debug, sqlx::Type)]
+#[sqlx(transparent)]
+struct Transparent(i32);
+
+// "Weak" enums map to an integer type indicated by #[repr]
+#[derive(PartialEq, Copy, Clone, Debug, sqlx::Type)]
+#[repr(i32)]
+enum Weak {
+    One = 0,
+    Two = 2,
+    Three = 4,
+}
+
+// "Strong" enums can map to TEXT or a custom enum
+#[derive(PartialEq, Debug, sqlx::Type)]
+#[sqlx(rename_all = "lowercase")]
+enum Color {
+    Red,
+    Green,
+    Blue,
+}
+
+test_type!(transparent(
+    MySql,
+    Transparent,
+    "0" == Transparent(0),
+    "23523" == Transparent(23523)
+));
+
+test_type!(weak_enum(
+    MySql,
+    Weak,
+    "0" == Weak::One,
+    "2" == Weak::Two,
+    "4" == Weak::Three
+));
+
+test_type!(strong_color_enum(MySql, Color, "'green'" == Color::Green));

tests/postgres-derives.rs

@@ -0,0 +1,86 @@
+use sqlx::Postgres;
+use sqlx_test::test_type;
+use std::fmt::Debug;
+
+// Transparent types are rust-side wrappers over DB types
+#[derive(PartialEq, Debug, sqlx::Type)]
+#[sqlx(transparent)]
+struct Transparent(i32);
+
+// "Weak" enums map to an integer type indicated by #[repr]
+#[derive(PartialEq, Copy, Clone, Debug, sqlx::Type)]
+#[repr(i32)]
+enum Weak {
+    One = 0,
+    Two = 2,
+    Three = 4,
+}
+
+// "Strong" enums can map to TEXT (25) or a custom enum type
+#[derive(PartialEq, Debug, sqlx::Type)]
+#[sqlx(postgres(oid = 25))]
+#[sqlx(rename_all = "lowercase")]
+enum Strong {
+    One,
+    Two,
+
+    #[sqlx(rename = "four")]
+    Three,
+}
+
+// TODO: Figure out a good solution for custom type testing
+// Records must map to a custom type
+// Note that all types are types in Postgres
+// #[derive(PartialEq, Debug, sqlx::Type)]
+// #[sqlx(postgres(oid = 12184))]
+// struct PgConfig {
+//     name: String,
+//     setting: Option<String>,
+// }
+
+test_type!(transparent(
+    Postgres,
+    Transparent,
+    "0" == Transparent(0),
+    "23523" == Transparent(23523)
+));
+
+test_type!(weak_enum(
+    Postgres,
+    Weak,
+    "0::int4" == Weak::One,
+    "2::int4" == Weak::Two,
+    "4::int4" == Weak::Three
+));
+
+test_type!(strong_enum(
+    Postgres,
+    Strong,
+    "'one'::text" == Strong::One,
+    "'two'::text" == Strong::Two,
+    "'four'::text" == Strong::Three
+));
+
+// TODO: Figure out a good solution for custom type testing
+// test_type!(record_pg_config(
+//     Postgres,
+//     PgConfig,
+//     // (CC,gcc)
+//     "(SELECT ROW('CC', 'gcc')::pg_config)"
+//         == PgConfig {
+//             name: "CC".to_owned(),
+//             setting: Some("gcc".to_owned()),
+//         },
+//     // (CC,)
+//     "(SELECT '(\"CC\",)'::pg_config)"
+//         == PgConfig {
+//             name: "CC".to_owned(),
+//             setting: None,
+//         },
+//     // (CC,"")
+//     "(SELECT '(\"CC\",\"\")'::pg_config)"
+//         == PgConfig {
+//             name: "CC".to_owned(),
+//             setting: Some("".to_owned()),
+//         }
+// ));

tests/postgres-types.rs

@@ -1,5 +1,11 @@
-use sqlx::Postgres;
-use sqlx_test::test_type;
+use sqlx::decode::Decode;
+use sqlx::encode::Encode;
+use sqlx::postgres::types::PgRecordEncoder;
+use sqlx::postgres::{PgQueryAs, PgTypeInfo, PgValue};
+use sqlx::{Cursor, Executor, Postgres, Row, Type};
+use sqlx_core::postgres::types::PgRecordDecoder;
+use sqlx_test::{new, test_type};
+use std::sync::atomic::{AtomicU32, Ordering};
 
 test_type!(null(
     Postgres,
@@ -87,3 +93,188 @@ mod chrono {
             )
     ));
 }
+
+#[cfg_attr(feature = "runtime-async-std", async_std::test)]
+#[cfg_attr(feature = "runtime-tokio", tokio::test)]
+async fn test_prepared_anonymous_record() -> anyhow::Result<()> {
+    let mut conn = new::<Postgres>().await?;
+
+    // Tuple of no elements is not possible
+    // Tuple of 1 element requires a concrete type
+    // Tuple with a NULL requires a concrete type
+
+    // Tuple of 2 elements
+    let rec: ((bool, i32),) = sqlx::query_as("SELECT (true, 23512)")
+        .fetch_one(&mut conn)
+        .await?;
+
+    assert_eq!((rec.0).0, true);
+    assert_eq!((rec.0).1, 23512);
+
+    // Tuple with an empty string
+    let rec: ((bool, String),) = sqlx::query_as("SELECT (true,'')")
+        .fetch_one(&mut conn)
+        .await?;
+
+    assert_eq!((rec.0).1, "");
+
+    // Tuple with a string with an interior comma
+    let rec: ((bool, String),) = sqlx::query_as("SELECT (true,'Hello, World!')")
+        .fetch_one(&mut conn)
+        .await?;
+
+    assert_eq!((rec.0).1, "Hello, World!");
+
+    // Tuple with a string with an emoji
+    let rec: ((bool, String),) = sqlx::query_as("SELECT (true,'Hello, 🐕!')")
+        .fetch_one(&mut conn)
+        .await?;
+
+    assert_eq!((rec.0).1, "Hello, 🐕!");
+
+    Ok(())
+}
+
+#[cfg_attr(feature = "runtime-async-std", async_std::test)]
+#[cfg_attr(feature = "runtime-tokio", tokio::test)]
+async fn test_unprepared_anonymous_record() -> anyhow::Result<()> {
+    let mut conn = new::<Postgres>().await?;
+
+    // Tuple of no elements is not possible
+    // Tuple of 1 element requires a concrete type
+    // Tuple with a NULL requires a concrete type
+
+    // Tuple of 2 elements
+    let mut cursor = conn.fetch("SELECT (true, 23512)");
+    let row = cursor.next().await?.unwrap();
+    let rec: (bool, i32) = row.get(0);
+
+    assert_eq!(rec.0, true);
+    assert_eq!(rec.1, 23512);
+
+    // Tuple with an empty string
+    let mut cursor = conn.fetch("SELECT (true, '')");
+    let row = cursor.next().await?.unwrap();
+    let rec: (bool, String) = row.get(0);
+
+    assert_eq!(rec.1, "");
+
+    // Tuple with a string with an interior comma
+    let mut cursor = conn.fetch("SELECT (true, 'Hello, World!')");
+    let row = cursor.next().await?.unwrap();
+    let rec: (bool, String) = row.get(0);
+
+    assert_eq!(rec.1, "Hello, World!");
+
+    // Tuple with a string with an emoji
+    let mut cursor = conn.fetch("SELECT (true, 'Hello, 🐕!')");
+    let row = cursor.next().await?.unwrap();
+    let rec: (bool, String) = row.get(0);
+
+    assert_eq!(rec.1, "Hello, 🐕!");
+
+    Ok(())
+}
+
+#[cfg_attr(feature = "runtime-async-std", async_std::test)]
+#[cfg_attr(feature = "runtime-tokio", tokio::test)]
+async fn test_prepared_structs() -> anyhow::Result<()> {
+    let mut conn = new::<Postgres>().await?;
+
+    //
+    // Setup custom types if needed
+    //
+
+    static OID_RECORD_EMPTY: AtomicU32 = AtomicU32::new(0);
+    static OID_RECORD_1: AtomicU32 = AtomicU32::new(0);
+
+    conn.execute(
+        r#"
+DO $$ BEGIN
+    CREATE TYPE _sqlx_record_empty AS ();
+    CREATE TYPE _sqlx_record_1 AS (_1 int8);
+EXCEPTION
+    WHEN duplicate_object THEN null;
+END $$;    
+    "#,
+    )
+    .await?;
+
+    let type_ids: Vec<(i32,)> = sqlx::query_as(
+        "SELECT oid::int4 FROM pg_type WHERE typname IN ('_sqlx_record_empty', '_sqlx_record_1')",
+    )
+    .fetch_all(&mut conn)
+    .await?;
+
+    OID_RECORD_EMPTY.store(type_ids[0].0 as u32, Ordering::SeqCst);
+    OID_RECORD_1.store(type_ids[1].0 as u32, Ordering::SeqCst);
+
+    //
+    // Record of no elements
+    //
+
+    struct RecordEmpty {}
+
+    impl Type<Postgres> for RecordEmpty {
+        fn type_info() -> PgTypeInfo {
+            PgTypeInfo::with_oid(OID_RECORD_EMPTY.load(Ordering::SeqCst))
+        }
+    }
+
+    impl Encode<Postgres> for RecordEmpty {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            PgRecordEncoder::new(buf).finish();
+        }
+    }
+
+    impl<'de> Decode<'de, Postgres> for RecordEmpty {
+        fn decode(_value: Option<PgValue<'de>>) -> sqlx::Result<Self> {
+            Ok(RecordEmpty {})
+        }
+    }
+
+    let _: (RecordEmpty, RecordEmpty) = sqlx::query_as("SELECT '()'::_sqlx_record_empty, $1")
+        .bind(RecordEmpty {})
+        .fetch_one(&mut conn)
+        .await?;
+
+    //
+    // Record of one element
+    //
+
+    #[derive(Debug, PartialEq)]
+    struct Record1 {
+        _1: i64,
+    }
+
+    impl Type<Postgres> for Record1 {
+        fn type_info() -> PgTypeInfo {
+            PgTypeInfo::with_oid(OID_RECORD_1.load(Ordering::SeqCst))
+        }
+    }
+
+    impl Encode<Postgres> for Record1 {
+        fn encode(&self, buf: &mut Vec<u8>) {
+            PgRecordEncoder::new(buf).encode(self._1).finish();
+        }
+    }
+
+    impl<'de> Decode<'de, Postgres> for Record1 {
+        fn decode(value: Option<PgValue<'de>>) -> sqlx::Result<Self> {
+            let mut decoder = PgRecordDecoder::new(value)?;
+
+            let _1 = decoder.decode()?;
+
+            Ok(Record1 { _1 })
+        }
+    }
+
+    let rec: (Record1, Record1) = sqlx::query_as("SELECT '(324235)'::_sqlx_record_1, $1")
+        .bind(Record1 { _1: 324235 })
+        .fetch_one(&mut conn)
+        .await?;
+
+    assert_eq!(rec.0, rec.1);
+
+    Ok(())
+}

tests/postgres.rs

@@ -1,12 +1,13 @@
 use futures::TryStreamExt;
 use sqlx::postgres::{PgPool, PgQueryAs, PgRow};
-use sqlx::{postgres::PgConnection, Connect, Connection, Executor, Row};
+use sqlx::{Connection, Executor, Postgres, Row};
+use sqlx_test::new;
 use std::time::Duration;
 
 #[cfg_attr(feature = "runtime-async-std", async_std::test)]
 #[cfg_attr(feature = "runtime-tokio", tokio::test)]
 async fn it_connects() -> anyhow::Result<()> {
-    let mut conn = connect().await?;
+    let mut conn = new::<Postgres>().await?;
 
     let value = sqlx::query("select 1 + 1")
         .try_map(|row: PgRow| row.try_get::<i32, _>(0))
@@ -21,7 +22,7 @@ async fn it_connects() -> anyhow::Result<()> {
 #[cfg_attr(feature = "runtime-async-std", async_std::test)]
 #[cfg_attr(feature = "runtime-tokio", tokio::test)]
 async fn it_executes() -> anyhow::Result<()> {
-    let mut conn = connect().await?;
+    let mut conn = new::<Postgres>().await?;
 
     let _ = conn
         .execute(
@@ -55,7 +56,7 @@ CREATE TEMPORARY TABLE users (id INTEGER PRIMARY KEY);
 #[cfg_attr(feature = "runtime-async-std", async_std::test)]
 #[cfg_attr(feature = "runtime-tokio", tokio::test)]
 async fn it_can_return_interleaved_nulls_issue_104() -> anyhow::Result<()> {
-    let mut conn = connect().await?;
+    let mut conn = new::<Postgres>().await?;
 
     let tuple =
         sqlx::query("SELECT NULL::INT, 10::INT, NULL, 20::INT, NULL, 40::INT, NULL, 80::INT")
@@ -89,7 +90,7 @@ async fn it_can_return_interleaved_nulls_issue_104() -> anyhow::Result<()> {
 #[cfg_attr(feature = "runtime-async-std", async_std::test)]
 #[cfg_attr(feature = "runtime-tokio", tokio::test)]
 async fn it_can_work_with_transactions() -> anyhow::Result<()> {
-    let mut conn = connect().await?;
+    let mut conn = new::<Postgres>().await?;
 
     conn.execute("CREATE TABLE IF NOT EXISTS _sqlx_users_1922 (id INTEGER PRIMARY KEY)")
         .await?;
@@ -141,7 +142,7 @@ async fn it_can_work_with_transactions() -> anyhow::Result<()> {
             .await?;
     }
 
-    conn = connect().await?;
+    conn = new::<Postgres>().await?;
 
     let (count,): (i64,) = sqlx::query_as("SELECT COUNT(*) FROM _sqlx_users_1922")
         .fetch_one(&mut conn)
@@ -210,7 +211,7 @@ async fn pool_smoke_test() -> anyhow::Result<()> {
 #[cfg_attr(feature = "runtime-async-std", async_std::test)]
 #[cfg_attr(feature = "runtime-tokio", tokio::test)]
 async fn test_describe() -> anyhow::Result<()> {
-    let mut conn = connect().await?;
+    let mut conn = new::<Postgres>().await?;
 
     let _ = conn
         .execute(
@@ -239,10 +240,3 @@ async fn test_describe() -> anyhow::Result<()> {
 
     Ok(())
 }
-
-async fn connect() -> anyhow::Result<PgConnection> {
-    let _ = dotenv::dotenv();
-    let _ = env_logger::try_init();
-
-    Ok(PgConnection::connect(dotenv::var("DATABASE_URL")?).await?)
-}