Automatically infer migration type (#2664)

sqlx-core/src/migrate/error.rs

@@ -24,6 +24,7 @@ pub enum MigrateError {
     #[error("migration {0} is newer than the latest applied migration {1}")]
     VersionTooNew(i64, i64),
 
+    #[deprecated = "migration types are now inferred"]
     #[error("cannot mix reversible migrations with simple migrations. All migrations should be reversible or simple migrations")]
     InvalidMixReversibleAndSimple,
 

sqlx-core/src/migrate/migration_type.rs

@@ -1,3 +1,5 @@
+use super::Migrator;
+
 /// Migration Type represents the type of migration
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub enum MigrationType {
@@ -71,4 +73,17 @@ impl MigrationType {
             MigrationType::ReversibleDown => "-- Add down migration script here\n",
         }
     }
+
+    pub fn infer(migrator: &Migrator, reversible: bool) -> MigrationType {
+        match migrator.iter().next() {
+            Some(first_migration) => first_migration.migration_type,
+            None => {
+                if reversible {
+                    MigrationType::ReversibleUp
+                } else {
+                    MigrationType::Simple
+                }
+            }
+        }
+    }
 }