test(fmt): cover baml.spawn paths in type positions

[sxlijin]

Summary

• add B-1509 regression coverage for baml.spawn.CancelToken in parameter, return, class-field, and generic-argument type positions
• document that formatter contextual identifiers cover both expression and type path segments
• keep the existing B-258 expression-position behavior covered alongside the new cases

Root cause

spawn is lexed as KW_SPAWN even when it appears as a namespace segment. The formatter previously expected a plain WORD in type paths. The shared contextual-keyword handling now accepts this valid parser output, but type-position coverage was missing.

Impact

Files with signatures such as tok: baml.spawn.CancelToken remain formatable and formatter behavior stays aligned with the parser across all reported type positions.

Validation

• cargo test -p baml_fmt --lib (125 passed)
• cargo fmt --all -- --check
• git diff --check

Linear: B-1509

Summary by CodeRabbit

• Bug Fixes

  • Improved formatting support for qualified type paths containing keyword-like segments, such as baml.spawn.CancelToken.
  • Ensured these paths remain intact across parameters, return types, class fields, and generic types.

• Tests

  • Added regression coverage verifying formatting succeeds and produces consistent, repeatable output.

[linear]

B-1509

[vercel]

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a86f5a5e-ec43-40a8-bb06-ebd5781c0294

📥 Commits

Reviewing files that changed from the base of the PR and between 077ad42 and f58bb5b.

📒 Files selected for processing (2)

• baml_language/crates/baml_fmt/src/ast/tokens.rs
• baml_language/crates/baml_fmt/src/lib.rs

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📝 Walkthrough

Walkthrough

The formatter documentation now describes keyword-like path segments in expressions and types. A regression test verifies that baml.spawn.CancelToken formats correctly in several type positions and remains idempotent.

Changes

Formatter contextual paths

Layer / File(s)	Summary
Document and test contextual type paths baml_language/crates/baml_fmt/src/ast/tokens.rs, baml_language/crates/baml_fmt/src/lib.rs	The Word documentation covers contextual path segments. A regression test checks baml.spawn.CancelToken in parameter types, return types, class fields, and generic map values.

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

Mergeability Score: ⚪ Minimal · up to f58bb

The PR preserves formatting for spawn namespace paths in type positions while keeping existing expression behavior covered; no actionable merge-blocking risk remains beyond normal checks.

Possibly related PRs

• BoundaryML/baml#3836: Related formatter changes for keyword path-segment support.
• BoundaryML/baml#4341: Introduces related contextual-keyword support for spawn.
• BoundaryML/baml#4107: Related formatter handling and regression coverage for contextual identifiers in type paths.

Suggested reviewers: codeshaunted, aaronvg

Poem

I hop through paths where keywords grow,
baml.spawn.CancelToken now formats so.
Types stay clear, each test runs bright,
Twice the same output, neat and right.
A tidy burrow for every byte.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the regression test for baml.spawn paths in type positions.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch sxlijin/B-1509-fmt-spawn-type-position

---

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[github-actions]

⏭️ Performance benchmarks were skipped

Perf benchmarks (CodSpeed) are opt-in on pull requests — they no longer run on every push. They always run automatically after merge to canary/main.

To run them on this PR, do any of the following, then push a commit (or re-run CI):

• Add RUN_CODSPEED=1 to the PR description, or
• Include run-perf or /perf in the PR title or any commit message.

[github-actions]

Binary size checks passed

✅ 7 passed

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	baml-cli	Linux	🔒 26.2 MB	11.1 MB	file	27.4 MB	-1.2 MB (-4.4%)	OK
✅	packed-program	Linux	🔒 16.9 MB	6.8 MB	file	18.6 MB	-1.7 MB (-8.9%)	OK
✅	baml-cli	macOS	🔒 20.4 MB	9.7 MB	file	21.3 MB	-913.9 KB (-4.3%)	OK
✅	packed-program	macOS	🔒 13.3 MB	6.0 MB	file	14.5 MB	-1.2 MB (-8.1%)	OK
✅	baml-cli	Windows	🔒 21.9 MB	9.9 MB	file	23.0 MB	-1.1 MB (-4.6%)	OK
✅	packed-program	Windows	🔒 14.1 MB	6.1 MB	file	15.5 MB	-1.4 MB (-9.1%)	OK
✅	bridge_wasm	WASM	15.5 MB	🔒 4.2 MB	gzip	4.6 MB	-437.3 KB (-9.5%)	OK

🔒 = the size this artifact is GATED on (ceiling + delta). Binaries gate on file size (installed binary); WASM gates on gzip (download size). The other size is shown for information only.

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Generated by cargo size-gate · workflow run

[sxlijin]

Closing as redundant: the reported formatter behavior was already fixed by #4341 (fix(fmt): accept contextual keywords as identifiers in name positions), merged as 061b224ea4. B-1509 now links that original fix; this PR only added explicit regression coverage for behavior already present on canary.