refactor(action): extract runReview from index.ts and test it (#169 slice 1)

[mmcky]

First slice of #169, the W1 gate. Deliberately the smallest one that proves the pattern: runReview was named in the issue's plan as the starting block because it changed twice in the last two releases.

The problem this starts on

src/index.ts is 1,579 lines (1,314 when the audit measured it — it has grown 265 lines since) with no usable exports, a bare run() at module scope, and import.meta.url at line 38. Importing any part of it executes the whole Action, so no test has ever reached it — verified again today: nothing under src/ imports it, and its one export (fetchBibliographies) has no importer anywhere. It is simultaneously the highest-churn file in the repo (24 commits in six months) and the only code that ships in dist-action/.

What moved

runReview → src/action/review.ts, with the glossary directory passed in as an argument. That argument is the whole trick: the import.meta.url derivation moves to src/runtime-paths.ts — the one module tests never import — and the entry point calls getBuiltInGlossaryDir() at the call site, so the extracted runner loads cleanly under Jest's CJS registry (F123). detectTargetLanguage becomes a pure function of the repo name instead of reading github.context, and the coreLogger adapter moves to src/action/core-logger.ts so the entry point and the extracted runners share one copy rather than growing a second. Sync and rebase keep their behaviour and now call the same glossary-path helper instead of repeating the path.join(__dirname, '..', 'glossary') incantation three times.

src/index.ts loses 124 lines and both the path and url imports.

Tests

17 new tests — the first ever written against entry-point logic: language detection (including the near-misses that must not match — three-letter suffixes, digits, uppercase), glossary resolution through the shared loader with the empty-string-to-undefined mapping for the custom path, the no-detectable-language warning path, reviewer construction and reviewPR argument threading, every action output including the shadow-gate would-auto-merge conditional and the #164 usage outputs, and error propagation to the shim's catch. Suite goes 1,516 → 1,533, all green, lint and format clean, and check-dev-refs passes.

Why this is safe to land

The extraction is semantics-preserving by construction, and the claim is checked rather than asserted:

• The set of core.setOutput calls in dist-action/index.js is identical before and after (diffed against a bundle built from the parent commit); the size delta is 261 bytes of module-wrapper overhead.
• action.yml's entry contract is untouched — still dist-action/run.cjs.
• import.meta.url resolves through the same esbuild banner as before. Both the old and new bundles derive it from the bundle's own __filename, so ../glossary still resolves to the repo-root glossary/ — worth stating explicitly, because a silent mis-resolution here would be exactly the success-shaped failure the tracker is about.

The module map in docs/developer/architecture.md gains the three new modules — its completeness guard (#168) caught their absence, which is the guard doing its job.

What this does not do

The remaining F<n> findings on #169 stay open: the two divergent FileToSync[] builders (F44, now at :381 and :1038), the error coercion (F36), the metadata.mode dispatch (F19) and the tri-state metadata parser (F139, F140). Those land in the following slices, with src/github-content.ts next. No behaviour change ships here, so nothing about the release gate changes.

Part of #169 · gates W1 (#259)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Refactors the GitHub Action entry point by extracting the REVIEW-mode runner into an importable module, enabling direct Jest coverage of previously untestable entry-point logic while keeping runtime-only import.meta.url usage isolated.

Changes:

• Extracts runReview (and detectTargetLanguage) from src/index.ts into src/action/review.ts, threading the built-in glossary directory as an explicit argument.
• Centralizes Action runtime glossary-path derivation in src/runtime-paths.ts and reuses it from sync/rebase code paths.
• Adds a focused Jest suite covering review-mode behavior (language detection, glossary loading, reviewer wiring, outputs, and error propagation) and updates the module map docs.

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/runtime-paths.ts	Introduces Action runtime path derivation helpers (module dir + built-in glossary dir).
src/index.ts	Removes inline REVIEW runner and import.meta.url path logic; delegates to extracted runner and shared helpers.
src/action/review.ts	New exported REVIEW-mode runner + pure detectTargetLanguage, extracted for testability.
src/action/core-logger.ts	New shared @actions/core → Logger adapter used by action runners.
src/action/tests/review.test.ts	Adds first direct tests for extracted entry-point review logic and outputs.
docs/developer/architecture.md	Updates module map to include the new Action/runtime modules.

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