feat(supabase_typegen): emit relation members from foreign key metadata

[spydon]

Stack 9/9 for SDK-1741, implementing SDK-1759. Base: lukasklingsbo/sdk-1741-8-typed-ranges.

PostgrestToOneRelation and PostgrestToManyRelation (8/9, #1799) had to be declared by hand. supabase_typegen already parsed the relationships array of the GeneratorMetadata document but only used it to mark foreign key columns; it now emits the relation members.

For every foreign key whose both ends are tables of the schema, the referencing table's namespace gets a PostgrestToOneRelation<SourceRow, TargetRow> named after the referenced table, and the referenced table's namespace gets a PostgrestToManyRelation<TargetRow, SourceRow> named after the referencing table, or a to-one relation when the metadata flags the key as one-to-one:

class Books {
  static const authors = PostgrestToOneRelation<BooksRow, AuthorsRow>('authors');
}
class Authors {
  static const books = PostgrestToManyRelation<AuthorsRow, BooksRow>('books');
}

client.table(Books.table).select([Books.id, Books.authors(Authors.name)]);
// select=id,authors(name)

Two rules handle names that would otherwise collide:

• Two keys from the same table to the same target make the plain table name ambiguous for PostgREST (PGRST201), so the embed carries the constraint hint, map!postgrest_table_mood_fkey, and the members are told apart by the key they follow: mapByMood on the referencing side, postgrestTableViaMood on the referenced side.
• A member that collides with a column, another relation or a core member name goes through the same disambiguation. By names a key this table holds, Via a key the other table holds.
• A self-referential key produces no member: PostgREST cannot tell the two directions of such an embed apart and needs a computed relationship, so a generated member could never be requested.

Keys into another schema get no member, since there is no generated row type to point at. Views take part when the metadata lists a relationship for them, as author_stats does in the fixture.

The type names of all tables are now claimed in one pass before any table is written, in the same order as before, so the relation types can reference each other; existing goldens are unchanged apart from the new members.

Summary by CodeRabbit

• New Features

  • Dart schema generation now includes typed one-to-one and one-to-many relation members for supported foreign keys.
  • Relation names are disambiguated when multiple keys connect the same tables, including self-referencing relationships.
  • Generated relation members support embedded-column selects and count modifiers.

• Documentation

  • Documented generated relation members and clarified limitations for cross-schema relationships and typed functions.

• Tests

  • Added coverage for relationship parsing, generation, naming, and embedded select behavior.

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• packages/supabase_typegen/README.md
• packages/supabase_typegen/lib/src/dart_generator.dart
• packages/supabase_typegen/test/dart_generator_test.dart
• packages/supabase_typegen/test/goldens/hostile_fixture.dart
• packages/supabase_typegen/test/goldens/hostile_schema.dart

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📝 Walkthrough

Walkthrough

The type generator now parses same-schema foreign-key metadata and emits typed one-to-one and to-many relation members. It disambiguates conflicting names, supports self-references, and validates generated relation projections.

Changes

Typed relationship generation

Layer / File(s)	Summary
Relationship metadata contract packages/supabase_typegen/lib/src/schema_description.dart, packages/supabase_typegen/lib/src/generator_metadata_parser.dart, packages/supabase_typegen/test/generator_metadata_parser_test.dart	SchemaDescription stores foreign-key metadata. The parser maps same-schema relationships and excludes cross-schema targets.
Relation member emission packages/supabase_typegen/lib/src/dart_generator.dart	The generator emits typed relation constants, assigns one-to-one or to-many cardinality, and disambiguates names for collisions and multiple foreign keys.
Generated relation validation and documentation packages/supabase_typegen/test/dart_generator_test.dart, packages/supabase_typegen/test/generated_schema_behavior_test.dart, packages/supabase_typegen/test/goldens/*, packages/supabase_typegen/README.md	Tests and golden schemas cover standard, reverse, self-referencing, ambiguous, and projection relations. The README documents generated relations and cross-schema limitations.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant MetadataParser
  participant SchemaDescription
  participant DartGenerator
  participant GeneratedNamespace
  MetadataParser->>SchemaDescription: Store same-schema relationship metadata
  SchemaDescription->>DartGenerator: Provide tables and relationships
  DartGenerator->>GeneratedNamespace: Emit typed relation constants

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Merge Risk: ⚪ Minimal · up to c09aa

The generator adds typed relation members for same-schema foreign keys while excluding self-referential members; current coverage shows no merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: generating relation members from foreign key metadata in supabase_typegen.

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• Commit unit tests in branch lukasklingsbo/sdk-1741-9-generated-relations

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[grdsdev]

Reviewed the diff: filter/escaping logic, ordering, embeds, ranges, aggregates and casts, and the typegen relation-naming are all correct and well tested.

[grdsdev]

Reviewed the diff (relation-member codegen from FK metadata). Traced self-reference and ambiguous-FK disambiguation against the golden fixtures — correct. Only minor codegen-time efficiency/duplication nits (e.g. _writeNamespace's collision loop could reuse _uniqueMemberNames), non-blocking.

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Actionable comments posted: 2

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Inline comments:
In `@packages/supabase_typegen/lib/src/dart_generator.dart`:
- Line 256: Update the self-referential relationship handling around
relationship.sourceTable == table.name so the parent branch emits the
foreign-key column syntax and the child branch emits the table-plus-column hint,
rather than using the plain table embed in both directions. Add an integration
test covering both recursive directions against the supported PostgREST version.

In `@packages/supabase_typegen/README.md`:
- Around line 16-18: Update the README description of PostgrestToOneRelation and
PostgrestToManyRelation to limit generated relation members to foreign keys
whose source and target tables both have generated row types in the selected
schema, replacing the current “every foreign key” wording while preserving the
table-name and constraint-hint details.

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📒 Files selected for processing (10)

• packages/supabase_typegen/README.md
• packages/supabase_typegen/lib/src/dart_generator.dart
• packages/supabase_typegen/lib/src/generator_metadata_parser.dart
• packages/supabase_typegen/lib/src/schema_description.dart
• packages/supabase_typegen/test/dart_generator_test.dart
• packages/supabase_typegen/test/generated_schema_behavior_test.dart
• packages/supabase_typegen/test/generator_metadata_parser_test.dart
• packages/supabase_typegen/test/goldens/hostile_fixture.dart
• packages/supabase_typegen/test/goldens/hostile_schema.dart
• packages/supabase_typegen/test/goldens/supabase_schema.dart

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