fix(merge): preserve repeatable directives on schema definitions

[aarne]

Description

mergeGraphQLNodes collects all directive definitions into a registry and passes it to every named-type merger, but not to mergeSchemaDefs — even though that function has accepted a directives parameter since #7249 (it was added to the signature but the call site was never updated). Without the registry, mergeDirectives cannot tell that a schema-level directive is declared repeatable, so repeated instances on schema definitions and extend schema extensions are collapsed into a single directive with merged arguments.

This PR passes the registry through at the call site (one line), enables the it.todo('supports multiple schema extensions') left behind by #7249, and adds a regression test for a repeatable directive on schema definitions across documents (which fails without the fix).

Federation @link mostly escaped this bug via repeatableLinkImports and the same-name/different-url carve-out in mergeDirectives; SDL-declared repeatable on SCHEMA directives had no such fallback.

Fixes #8348

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• New regression test keeps repeatable directives on schema definitions across documents — fails without the one-line fix, passes with it
• Enabled the previously commented-out supports multiple schema extensions todo test
• Full packages/merge and packages/schema suites pass (194 tests)

Test Environment:

• OS: Linux
• @graphql-tools/merge: master (9.2.2)
• NodeJS: 26

Checklist:

• I have followed the CONTRIBUTING doc and the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests and linter rules pass locally with my changes

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 7dabb1a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@graphql-tools/merge	Patch
@graphql-tools/schema	Patch
graphql-tools	Patch
@graphql-tools/load	Patch
@graphql-tools/mock	Patch
@graphql-tools/node-require	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Fixed schema merging so repeatable directives on schema definitions and extensions are preserved separately with their distinct arguments.
  • Ensured repeatable @link and @tag directives remain available and retain their document order.

• Tests

  • Added coverage for repeatable directives across multiple schema definitions and extensions.

Walkthrough

The schema merge path now passes collected directive definitions to mergeSchemaDefs. Tests verify that repeatable @link and @tag directives remain separate and preserve their order.

Changes

Schema directive merging

Layer / File(s)	Summary
Preserve repeatable schema directives packages/merge/src/typedefs-mergers/merge-nodes.ts, packages/merge/tests/merge-typedefs.spec.ts, .changeset/merge-schema-def-repeatable-directives.md	mergeGraphQLNodes passes the collected directives map to mergeSchemaDefs. Tests cover repeatable schema-level @link directives on extensions and repeatable @tag directives across definitions. A patch changeset documents the fix.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• ardatan/graphql-tools#6964: Both PRs preserve distinct schema-level @link directives during merging.
• ardatan/graphql-tools#7249: This PR extends repeatable-directive merging for schema-level @link and @tag directives.

Suggested reviewers: ardatan

Poem

I’m a rabbit guarding tags in a row,
Keeping each directive where it should go.
@link stays distinct, @tag keeps its place,
The schema merge now runs with grace.
Hop, hop—repeatable facts remain!

🚥 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.
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.
Title check	✅ Passed	The title clearly and concisely describes the primary fix for preserving repeatable directives on schema definitions.
Description check	✅ Passed	The description directly explains the schema merging bug, the implementation fix, regression tests, and test results.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ardatan]

Thanks @aarne !