parser: reject illegal raw identifiers in attribute access

askama_parser/src/expr.rs

@@ -42,61 +42,47 @@ struct Allowed {
 
 fn check_expr<'a>(expr: &WithSpan<'a, Expr<'a>>, allowed: Allowed) -> Result<(), ParseErr<'a>> {
     match &expr.inner {
-        Expr::Var(name) => {
+        &Expr::Var(name) => {
             // List can be found in rust compiler "can_be_raw" function (although in our case, it's
             // also used in cases like `match`, so `self` is allowed in this case).
-            if (!allowed.super_keyword && *name == "super") || matches!(*name, "crate" | "Self") {
+            if (!allowed.super_keyword && name == "super") || matches!(name, "crate" | "Self") {
-                Err(winnow::error::ErrMode::Cut(ErrorContext::new(
+                Err(err_reserved_identifier(name))
-                    format!("`{name}` cannot be used as an identifier"),
+            } else if !allowed.underscore && name == "_" {
-                    expr.span,
+                Err(err_underscore_identifier(name))
-                )))
-            } else if !allowed.underscore && *name == "_" {
-                Err(winnow::error::ErrMode::Cut(ErrorContext::new(
-                    "reserved keyword `_` cannot be used here",
-                    expr.span,
-                )))
             } else {
                 Ok(())
             }
         }
-        Expr::IsDefined(var) | Expr::IsNotDefined(var) => {
+        &Expr::IsDefined(var) | &Expr::IsNotDefined(var) => {
-            if *var == "_" {
+            if var == "_" {
-                Err(winnow::error::ErrMode::Cut(ErrorContext::new(
+                Err(err_underscore_identifier(var))
-                    "reserved keyword `_` cannot be used here",
-                    expr.span,
-                )))
             } else {
                 Ok(())
             }
         }
         Expr::Path(path) => {
-            if let [name] = path.as_slice() {
+            if let &[name] = path.as_slice() {
                 if !crate::can_be_variable_name(name) {
-                    return Err(winnow::error::ErrMode::Cut(ErrorContext::new(
+                    return Err(err_reserved_identifier(name));
-                        format!("`{name}` cannot be used as an identifier"),
-                        *name,
-                    )));
                 }
             }
             Ok(())
         }
-        Expr::BoolLit(_)
-        | Expr::NumLit(_, _)
-        | Expr::StrLit(_)
-        | Expr::CharLit(_)
-        | Expr::Attr(_, _)
-        | Expr::Filter(_)
-        | Expr::NamedArgument(_, _)
-        | Expr::RustMacro(_, _)
-        | Expr::Try(_)
-        | Expr::FilterSource
-        | Expr::LetCond(_) => Ok(()),
         Expr::Array(elems) | Expr::Tuple(elems) | Expr::Concat(elems) => {
             for elem in elems {
                 check_expr(elem, allowed)?;
             }
             Ok(())
         }
+        Expr::Attr(elem, attr) => {
+            if attr.name == "_" {
+                Err(err_underscore_identifier(attr.name))
+            } else if !crate::can_be_variable_name(attr.name) {
+                Err(err_reserved_identifier(attr.name))
+            } else {
+                check_expr(elem, Allowed::default())
+            }
+        }
         Expr::Index(elem1, elem2) | Expr::BinOp(_, elem1, elem2) => {
             check_expr(elem1, Allowed::default())?;
             check_expr(elem2, Allowed::default())
@@ -130,9 +116,33 @@ fn check_expr<'a>(expr: &WithSpan<'a, Expr<'a>>, allowed: Allowed) -> Result<(),
             "unreachable",
             expr.span,
         ))),
+        Expr::BoolLit(_)
+        | Expr::NumLit(_, _)
+        | Expr::StrLit(_)
+        | Expr::CharLit(_)
+        | Expr::Filter(_)
+        | Expr::NamedArgument(_, _)
+        | Expr::RustMacro(_, _)
+        | Expr::Try(_)
+        | Expr::FilterSource
+        | Expr::LetCond(_) => Ok(()),
     }
 }
 
+fn err_underscore_identifier(name: &str) -> winnow::error::ErrMode<ErrorContext<'_>> {
+    winnow::error::ErrMode::Cut(ErrorContext::new(
+        "reserved keyword `_` cannot be used here",
+        name,
+    ))
+}
+
+fn err_reserved_identifier(name: &str) -> winnow::error::ErrMode<ErrorContext<'_>> {
+    winnow::error::ErrMode::Cut(ErrorContext::new(
+        format!("`{name}` cannot be used as an identifier"),
+        name,
+    ))
+}
+
 #[derive(Clone, Debug, PartialEq)]
 pub enum Expr<'a> {
     BoolLit(bool),

fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-6617490908315648

@@ -0,0 +1 @@
+˙˙˙{{crate.4}}˙˙˙˙e˙  

testing/tests/ui/crate_identifier.rs

@@ -148,4 +148,32 @@ struct PathElemSelfType2 {
     a: u8,
 }
 
+#[derive(Template)]
+#[template(ext = "html", source = "{{ Self.4 }}")]
+struct InvalidRawIdentifierSelfTyInAttr1;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ super.4 }}")]
+struct InvalidRawIdentifierSuperInAttr1;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ crate.4 }}")]
+struct InvalidRawIdentifierCrateInAttr1;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ self.Self.4 }}")]
+struct InvalidRawIdentifierSelfTyInAttr2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ self.super.4 }}")]
+struct InvalidRawIdentifierSuperInAttr2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ self.crate.4 }}")]
+struct InvalidRawIdentifierCrateInAttr2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ self.self.4 }}")]
+struct InvalidRawIdentifierSelfInAttr;
+
 fn main() {}

testing/tests/ui/crate_identifier.stderr

@@ -237,3 +237,59 @@ error: `Self` cannot be used as an identifier
     |
 146 | #[template(ext = "html", source = "{% match a %}{% when self::a::b::Self %}{% endmatch %}")]
     |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `Self` cannot be used as an identifier
+ --> <source attribute>:1:3
+       "Self.4 }}"
+   --> tests/ui/crate_identifier.rs:152:35
+    |
+152 | #[template(ext = "html", source = "{{ Self.4 }}")]
+    |                                   ^^^^^^^^^^^^^^
+
+error: `super` cannot be used as an identifier
+ --> <source attribute>:1:3
+       "super.4 }}"
+   --> tests/ui/crate_identifier.rs:156:35
+    |
+156 | #[template(ext = "html", source = "{{ super.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^
+
+error: `crate` cannot be used as an identifier
+ --> <source attribute>:1:3
+       "crate.4 }}"
+   --> tests/ui/crate_identifier.rs:160:35
+    |
+160 | #[template(ext = "html", source = "{{ crate.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^
+
+error: `Self` cannot be used as an identifier
+ --> <source attribute>:1:8
+       "Self.4 }}"
+   --> tests/ui/crate_identifier.rs:164:35
+    |
+164 | #[template(ext = "html", source = "{{ self.Self.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^^^^^
+
+error: `super` cannot be used as an identifier
+ --> <source attribute>:1:8
+       "super.4 }}"
+   --> tests/ui/crate_identifier.rs:168:35
+    |
+168 | #[template(ext = "html", source = "{{ self.super.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^^^^^^
+
+error: `crate` cannot be used as an identifier
+ --> <source attribute>:1:8
+       "crate.4 }}"
+   --> tests/ui/crate_identifier.rs:172:35
+    |
+172 | #[template(ext = "html", source = "{{ self.crate.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^^^^^^
+
+error: `self` cannot be used as an identifier
+ --> <source attribute>:1:8
+       "self.4 }}"
+   --> tests/ui/crate_identifier.rs:176:35
+    |
+176 | #[template(ext = "html", source = "{{ self.self.4 }}")]
+    |                                   ^^^^^^^^^^^^^^^^^^^