fix(jsts): stop reporting prettier as eslint, and distil prettier's real output

[fajarhide]

Closes #114

Problem — three compounding prettier defects

npm run format (prettier --write ., which rewrote files across 109 paths) came out as:

$ omni exec npm run format
eslint: no problems found   ⏺ 99.5% reduction (4.6 KB → 25 B)

A destructive command reported as a clean run of a different tool that never ran.

1. Wrong tool (the false claim). is_eslint_output matched the bare word eslint — which appears as a filename, eslint.config.js, in prettier's file list — and eslint is checked before prettier, so prettier output went to distill_eslint → eslint: no problems found. Same substring-in-data trap as CloudDistiller misidentifies any 'kubectl get <resource> -A' table as a pod table, reporting healthy objects as errors #105/Composite npm scripts are distilled as a single tool: npm run verify collapses 19.5 KB to tsc: no errors, discarding four of five gates #106.
2. Dead detector. is_prettier_output only matched lowercase checking /reformatted , but prettier prints Checking formatting… and [warn]. It never fired on real prettier output.
3. Wrong parser. distill_prettier parsed black's reformatted N files summary, which prettier never prints — so both counters stayed 0 and a failing --check and a successful --write both rendered prettier: 0 files reformatted, 0 unchanged ("nothing to do" in the one case the gate is red).

Fix

• eslint detection anchors on shape, not a filename-collidable substring: ✖ N problems (, a rule id (@typescript-eslint/…), or a <line>:<col> error|warning finding line.
• prettier detection matches what prettier actually prints: Checking formatting, [warn], Code style issues, a <path> <n>ms write line, or a prettier echo (any case).
• distill_prettier rewritten per mode: --check surfaces the offending filenames (prettier --check: N file(s) need formatting); --write reports N reformatted, M unchanged and names the changed files (capped); declines (returns input) rather than fabricate a count when neither mode is recognisable.

Verified (real binary + snapshots)

$ omni exec npm run format      # after
prettier --write: 3 reformatted, 6 unchanged
  src/lib/i18n.tsx
  src/routes/index.tsx
  src/components/Header.tsx

prettier --check → prettier --check: 2 file(s) need formatting + the filenames (was prettier: 0 files reformatted, 0 unchanged).

Snapshot tests added for both modes (prettier_write.txt, prettier_check.txt). Teeth: restoring the eslint filename match reverts --write to the exact reported eslint: no problems found; restoring the fix keeps the prettier summary. The existing eslint / vitest / tsc snapshots are unchanged.

Gates: cargo fmt / clippy -D warnings / cargo test (1048 passed, 0 failed) on local Homebrew 1.94.0, not CI's pinned 1.97.0 — CI is the source of truth for clippy.

Not fixed here

Report's defect 4 — prettier --check output reordered with the [warn] filename dropped — is an untraced stdout/stderr-ordering observation (omni exec inherits stderr, so the [warn] lines never reach the distiller there; the merged hook payload is fine). The reporter flagged it as observation, not diagnosis; left for its own issue. This distiller fix is order-independent (it scans all lines for [warn]).

PR Auto Describe

Summary

Fixed three compounding defects in distillers::jsts that misidentified prettier output as eslint: is_eslint_output matched filenames containing "eslint", is_prettier_output only matched lowercase strings that never fired on real prettier output, and distill_prettier parsed black's summary format that prettier never prints. Added snapshot tests for both --check and --write modes.

Key Changes

• is_eslint_output: Anchored detection on real eslint output shapes ( problems (, rule ids, finding lines) — no longer matches bare word "eslint" in filenames
• is_prettier_output: Matches capitalized "Checking formatting…", [warn], "Code style issues", and prettier's <path> <n>ms file lines
• distill_prettier: Rewritten to parse prettier's real output per mode; declines (returns input) rather than fabricate zeros when output is unrecognized

Detailed Breakdown

• New is_eslint_finding_line: Parses eslint's <line>:<col> error|warning … shape — requires all-digit line/col and an error/warning keyword token
• New is_prettier_write_line: Detects <path> <n>ms pattern by verifying a token ending in ms with numeric prefix
• New capped_lines: Helper renders file lists with 20-item cap and … and N more tail
• distill_prettier --check: Extracts [warn] <path> lines, reports count and capped filenames, or "all files formatted" if clean
• distill_prettier --write: Separates changed vs (unchanged) files from <path> <n>ms lines, reports counts and changed filenames capped
• Test fixtures added: tests/fixtures/prettier_check.txt, tests/fixtures/prettier_write.txt
• Snapshot tests added: test_jsts_prettier_check, test_jsts_prettier_write

Notes

The --check stdout/stderr ordering issue noted in #114 is out of scope — filed separately.

Last updated: 2026-07-21 08:57:28