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Fix @join__field emission for Fed v1 @external and @override+ @requires edge cases#284

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n1ru4l merged 2 commits intokamilkisiela-patch-1from
kamil-fix
Mar 16, 2026
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Fix @join__field emission for Fed v1 @external and @override+ @requires edge cases#284
n1ru4l merged 2 commits intokamilkisiela-patch-1from
kamil-fix

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@kamilkisiela kamilkisiela commented Mar 10, 2026 •
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This PR corrects supergraph's @join__field emission in a few edge cases where emitted metadata could be incorrect or redundant.

  • Use subgraph-local key usage when deciding whether to drop Federation v1 @join__field(external:true)
  • Avoid emitting redundant @join__field(external: true) metadata when a field is only required through overridden paths
  • Tighten @join__field emission around @override and interface type fields.

This aligns emitted supergraph metadata with Apollo Gateway's requirements.
Added Apollo supergraph validation in testkit to catch compatibility regressions earlier.

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Summary of Changes

Hello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors and enhances the supergraph composition process, specifically addressing how @override and @provides directives are handled. The changes aim to improve the accuracy and efficiency of supergraph generation by centralizing logic for @join__field emission and introducing new validation steps. This ensures that the composed supergraph correctly reflects the intended schema, particularly for complex federation scenarios involving field overrides and external fields.

Highlights

  • Supergraph Composition Refinement: Refactored the supergraph composition logic, specifically enhancing the handling of @override and @provides directives to ensure more accurate and efficient supergraph generation.
  • Federation v1 External Field Optimization: Introduced new logic to drop unused external fields in Federation v1 supergraphs, optimizing the generated SDL by removing redundant directives.
  • Enhanced Supergraph Validation: Integrated new validation steps using @apollo/federation-internals to detect and prevent composition issues earlier in the testing process.
  • Improved Test Coverage: Expanded test coverage for @override scenarios, including specific assertions for __typename handling and the correct emission of @join__field directives in the supergraph SDL.
  • Dependency Update: Added @apollo/federation-internals as a development dependency to support the new validation capabilities.
Changelog
  • tests/override-with-label.spec.ts
    • Added new assertions to verify the generated supergraph SDL for specific @override and @join__field configurations.
  • tests/shared/testkit.ts
    • Introduced supergraph validation using @apollo/federation-internals to detect composition issues earlier in tests.
    • Added a new import for ApolloSupergraph.
  • tests/subgraph/errors/EXTERNAL_UNUSED.spec.ts
    • Removed redundant directive definitions from test type definitions.
  • tests/subgraph/key-fields.spec.ts
    • Updated test to assert specific supergraph SDL content for @provides and __typename handling.
    • Added @shareable directives to test schemas.
  • package.json
    • Added @apollo/federation-internals as a development dependency.
  • pnpm-lock.yaml
    • Updated the pnpm lockfile to reflect the new dependency.
  • src/subgraph/validation/rules/elements/provides.ts
    • Refined the @provides rule to explicitly exclude __typename when marking fields as provided.
    • Refactored imports for GraphQL types.
  • src/supergraph/composition/object-type.ts
    • Refactored the logic for emitting @join__field directives.
    • Added functions for dropping unused Federation v1 external fields, collecting override information, and building join field ASTs.
    • Refined conditions for retaining object type join types.
    • Updated provideUsedOverriddenValue to check for inGraphs instanceof Set.
    • Modified shouldKeepObjectTypeJoinTypeInGraph logic to separate hasDefinition and keys.length > 0 checks and added a condition for objectTypeInGraph.extension && !hasOnlyOverriddenRequires.
Activity
  • No specific activity has been recorded for this pull request yet.
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Code Review

This pull request introduces a significant and valuable refactoring of the @override composition logic, centralizing it to improve maintainability and fix complex bugs related to interactions with @requires and interfaces. The addition of supergraph validation using @apollo/federation-internals in the testkit is an excellent enhancement for ensuring correctness. The code is much cleaner and more consistent now. I have one suggestion to further improve the new logic by reducing some code duplication.

@kamilkisiela kamilkisiela changed the title fix Fix @join__field emission for Fed v1 @external and @override+ @requires edge cases Mar 10, 2026
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github-actions bot commented Mar 10, 2026

🚀 Snapshot Release (alpha)

The latest changes of this PR are available as alpha on npm (based on the declared changesets):

Package Version Info
@theguild/federation-composition 0.22.1-alpha-20260310152804-4b0d25c0c6f27415ec843256b5b7673029d46af5 npm ↗︎ unpkg ↗︎

@kamilkisiela kamilkisiela marked this pull request as ready for review March 10, 2026 15:29
@n1ru4l n1ru4l merged commit 2103359 into kamilkisiela-patch-1 Mar 16, 2026
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@n1ru4l n1ru4l deleted the kamil-fix branch March 16, 2026 09:36
kamilkisiela added a commit that referenced this pull request Mar 16, 2026
@kamilkisiela
Fix @join__field emission for Fed v1 @external and @override+ `…
de2d7db 
…@requires` edge cases (#284)

This PR corrects supergraph's `@join__field` emission in a few edge
cases where emitted metadata could be incorrect or redundant.

- Use subgraph-local key usage when deciding whether to drop Federation
v1 `@join__field(external:true)`
- Avoid emitting redundant `@join__field(external: true)` metadata when
a field is only required through overridden paths
- Tighten `@join__field` emission around `@override` and interface type
fields.

This aligns emitted supergraph metadata with Apollo Gateway's
requirements.
Added Apollo supergraph validation in testkit to catch compatibility
regressions earlier.
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@n1ru4l n1ru4l n1ru4l approved these changes

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