fix: fix unsupported type diff false positives (#5633)

[TML-1493](https://linear.app/prisma-company/issue/TML-1493/fix-unsupported-data-type-issue)

The extension type changes accidentally caused unsupported types to
produce diffs because they weren't considered equal to
`PostgresType::Unknown`, which is what the introspection infers for
unknown columns now.

`None` (no native type defined in schema) and
`Some(PostgresType::Unknown(_))` (unknown type found in introspection)
should be compared using the type name.

The existing type name check is broken though because it compares
`columns.previous` to `columns.previous`. I left that behavior unchanged
intentionally, because the diffs it produces are somewhat broken. They
generate `ALTER TYPE` statements from `full_data_type`, which isn't
always valid, for example when the column type is `vector(3)`, the
`full_data_type` is `vector` so the statement ends up being invalid:
`SET DATA TYPE vector`. This functionality works fine for types without
modifiers though like plain `geometry`. As of this PR though, the diffs
should never occur.

Fixes: prisma/prisma#28237

Author: jacek-prisma

schema-engine/connectors/sql-schema-connector/src/flavour/postgres/schema_differ.rs

@@ -382,10 +382,10 @@ fn postgres_column_type_change(columns: MigrationPair<TableColumnWalker<'_>>) ->
                 Some(RiskyCast)
             }
         }
-        // Unsupported types will have None as Native type
-        (None, Some(_)) => Some(RiskyCast),
-        (Some(_), None) => Some(RiskyCast),
-        (None, None)
+        // Unsupported types will have None as Native type when defined in the Prisma schema.
+        // When introspected, we get an Unknown type with name and args.
+        (None | Some(PostgresType::Unknown(_, _)), None | Some(PostgresType::Unknown(_, _)))
+        // TODO: this diffs columns.previous with columns.previous, which is incorrect
             if columns.previous.column_type().full_data_type == columns.previous.column_type().full_data_type =>
         {
             None

schema-engine/sql-migration-tests/tests/migrations/postgres/extensions.rs

@@ -1,5 +1,5 @@
 use indoc::indoc;
-use psl::SourceFile;
+use psl::{SourceFile, parser_database::NoExtensionTypes};
 use schema_core::{ExtensionType, ExtensionTypeConfig, schema_connector::DiffTarget};
 use sql_migration_tests::test_api::*;
 
@@ -581,3 +581,72 @@ fn diff_extension_type_unchanged_db_type_modifiers(api: TestApi) {
     -- This is an empty migration."#]]
     .assert_eq(&diff);
 }
+
+#[test_connector(tags(Postgres), exclude(CockroachDb))]
+fn diff_unchanged_unsupported_type(api: TestApi) {
+    let dm = indoc! {r#"
+        generator client {
+          provider = "prisma-client"
+        }
+
+        datasource db {
+          provider = "postgresql"
+          url      = "env(TEST_DATABASE_URL)"
+        }
+
+        model A {
+          id   Int     @id @default(autoincrement())
+          data Unsupported("vector")?
+        }
+    "#};
+
+    let extensions = NoExtensionTypes;
+
+    api.raw_cmd("CREATE EXTENSION IF NOT EXISTS vector");
+    api.raw_cmd("CREATE TABLE \"A\" (\"id\" SERIAL PRIMARY KEY, \"data\" vector(3))");
+
+    let diff = api.connector_diff(
+        DiffTarget::Database,
+        DiffTarget::Datamodel(vec![("schema.prisma".into(), SourceFile::new_static(dm))], &extensions),
+        None,
+    );
+
+    expect![[r#"
+    -- This is an empty migration."#]]
+    .assert_eq(&diff);
+}
+
+#[test_connector(tags(Postgres), exclude(CockroachDb))]
+fn diff_changed_unsupported_type(api: TestApi) {
+    let dm = indoc! {r#"
+        generator client {
+          provider = "prisma-client"
+        }
+
+        datasource db {
+          provider = "postgresql"
+          url      = "env(TEST_DATABASE_URL)"
+        }
+
+        model A {
+          id   Int     @id @default(autoincrement())
+          data Unsupported("vector")?
+        }
+    "#};
+
+    let extensions = NoExtensionTypes;
+
+    api.raw_cmd("CREATE EXTENSION IF NOT EXISTS vector");
+    api.raw_cmd("CREATE EXTENSION IF NOT EXISTS postgis");
+    api.raw_cmd("CREATE TABLE \"A\" (\"id\" SERIAL PRIMARY KEY, \"data\" geometry)");
+
+    let diff = api.connector_diff(
+        DiffTarget::Database,
+        DiffTarget::Datamodel(vec![("schema.prisma".into(), SourceFile::new_static(dm))], &extensions),
+        None,
+    );
+
+    // TODO: this should produce 'ALTER TABLE "A" ALTER COLUMN "data" SET DATA TYPE geometry;',
+    // but unsupported column diffing is currently broken.
+    expect!["-- This is an empty migration."].assert_eq(&diff);
+}