feat(typescript): support .mts/.cts as TypeScript

[joptimus]

What

Index, resolve, and analyze .mts (ESM) and .cts (CommonJS) TypeScript module files as TypeScript instead of skipping them as unknown.

Why

The TypeScript language spec only mapped .ts/.tsx, so .mts/.cts files were detected as unknown and skipped by the indexer (issue #288). .cts is included because it is the paired CommonJS TypeScript module extension and shares the same parser and resolver path.

How

• Detection/parsing: register .mts/.cts in the TypeScript language spec. They propagate to EXTENSION_TO_LANGUAGE automatically (it is derived from the spec registry) and route to the plain TypeScript grammar; only .tsx needs the JSX variant, so .mts/.cts fall through correctly.
• Import resolution (all three resolvers): resolve extensionless imports to .mts/.cts, including directory-barrel index.mts/index.cts:
  • relative resolver (resolvers/typescript.py): probe list + /index.mts,/index.cts + the fake-extension fallback loop.
  • tsconfig path-alias resolution (tsconfig_resolver.py): _TS_EXTENSIONS, _INDEX_FILES.
  • workspace exports (resolvers/ts_workspace.py): _PROBE_EXTENSIONS.
• Test-file classification: once .mts/.cts files are indexed they flow into analysis, so add .test.mts/.spec.cts etc. to every test-classification list to avoid misflagging: dead-code never-flag, health engine._is_test_file and engine._has_paired_test_file, hidden_coupling, coverage detector (_TEST_FILE_SUFFIXES and paired_test_file), and coverage_gap.

Tests

TDD for each layer: language detection, parser smoke tests, all three resolvers (direct + index-barrel, .mts and .cts), dead-code never-flag, and the health classifiers (including the engine paired-test helper for a .mts source). Full affected-area regression: 1136 passed, 2 xfailed.

Out of scope (follow-up)

Framework-edge route detection for module-script extensions (next_app.py, remix.py), and full Node ESM/CJS output-mapping semantics.

This change is Python-only and does not touch packages/web.

Closes #288

[repowise-bot]

✅ Health: 7.5 (unchanged)
_{2 files moved · 5 hotspots · 5 hidden couplings · 1 dead-code finding}

File	Score	Δ	Why
.../resolvers/ts_workspace.py	6.6 → 4.5	▼ -2.1	score drifted on re-parse — no PR-attributable biomarkers
.../resolvers/typescript.py	9.3 → 8.6	▼ -0.7	nested complexity, complex method

💡 .../resolvers/typescript.py: Flatten the control flow. Pull early-return guards to the top, extract the deepest branch into a helper, and consider replacing nested conditionals with a strategy table or dispatch dict.

🔥 Hotspot touched

• .../parser/test_typescript.py — 1 commits/90d, 1 dependents · primary owner: Raghav Chamadiya (100%)
• .../biomarkers/hidden_coupling.py — 1 commits/90d, 2 dependents · primary owner: Raghav Chamadiya (100%)
• .../health/engine.py — 3 commits/90d, 1 dependents · primary owner: Raghav Chamadiya (100%)

2 more

• .../ingestion/test_traverser.py — 5 commits/90d, 0 dependents · primary owner: RaghavChamadiya (58%)
• .../dead_code/constants.py — 8 commits/90d, 1 dependents · primary owner: Raghav Chamadiya (88%)

🔗 Hidden coupling

• .../dead_code/constants.py co-changes with these files (not in this PR):
  • .../dead_code/analyzer.py (7× — 🟢 routine)
  • .../ingestion/parser.py (5× — 🟢 routine)
• .../ingestion/test_traverser.py co-changes with .../ingestion/traverser.py (3× — 🟢 routine) — not in this PR.
• .../health/engine.py co-changes with these files (not in this PR):
  • docs/CODE_HEALTH.md (2× — 🟢 routine)
  • .../biomarkers/README.md (2× — 🟢 routine)

Dead code

• 💀 .../resolvers/ts_workspace.py get_or_build_workspace_map (confidence 1.00)

👀 Suggested reviewers @RaghavChamadiya

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📊 Full report · ⭐ Star Repowise · 📥 Install bot · Last updated 2026-05-29 15:30 UTC
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