test-conformance's macos-latest leg (Phase 2, #4591) has been running the
same 546-file, Windows-oriented conformance-tier list as windows-latest --
built from signals like windows-shell-token/windows-env-var that have
nothing to do with macOS. Issue #4593 asked for macOS coverage sized to
its own evidence-backed surface (zsh dispatch, case-sensitivity, darwin-
specific behavior) instead.
Issue #4593 was filed before Phase 5 (#4603) existed and referenced
updating test-full's macOS legs -- that job is gone. Corrected the issue's
body before any code was touched: the "shrink from full replay" half of
the original ask was already done by Phase 5; what remained was narrowing
the still-Windows-oriented tier macOS was inheriting.
Two design assumptions were measured and rejected before accepting a
design (documented in docs/adr/4593-macos-conformance-tier-architecture.md):
- Reusing the general tier's signals minus its 3 Windows-specific
categories barely narrows anything (546 -> 424, 78% retained) -- most
files match multiple signals and only need one to survive exclusion.
- A standalone CRLF/autocrlf signal, despite the issue naming
"CRLF-checkout behavior": even narrowed to /\bCRLF\b|autocrlf/i it hit
143/930 files. Root cause: CRLF is primarily a Windows checkout concern
in this codebase (ADR-1703 files it under DEFECT.WINDOWS-TEST-
PORTABILITY), so the signal was really re-selecting Windows-relevant
files already covered by the general tier, not narrowing macOS
specifically.
Built 5 new, genuinely macOS-specific signals instead: darwin-literal
(darwin alone, not the general tier's win32-OR-darwin), zsh-dispatch,
case-sensitivity, plus chmod-mode-bit and symlink-keyword reused verbatim
from the general tier (genuinely Unix-relevant, not Windows-motivated).
Measured against the real tree: 196 of 930 eligible unit-suite files
(21%), versus the general tier's 546 (59%) -- a real, evidence-backed
narrowing.
scripts/gen-platform-conformance-tier.cjs gains classifyMacosContent/
classifyMacosTree/renderMacosGeneratedFile and a --target windows
(default, unchanged)/--target macos CLI flag, so the same generator
produces two independent, gated outputs rather than needing a second
script. New committed output: scripts/lib/macos-conformance-tier.
generated.cjs. .github/workflows/test.yml's test-conformance job: only
the macos-latest leg's file-list source changes; windows-latest is
byte-for-byte untouched. New shipped-file ripples handled proactively
(19 install-tree fixtures regenerated, bin/install.js registered).
An isolated code-review pass found one real defect: the ADR's per-
category count table had drifted by 1 (zsh-dispatch, case-sensitivity)
because the new test file's own fixture strings joined the tree it
classifies after the table was authored -- fixed, with the union total
(196, what CI actually gates on) confirmed unaffected. An isolated
security-review pass found no qualifying findings.
The ADR also records an explicit requirement for any future widening
proposal: check whether the motivating regression is already covered by
Phase 1's no-rendered-text-length-assert lint rule (#4590) before
re-proposing full macOS/Linux parity, since that is exactly what #4421's
root cause was (a rendered-text-length assertion, not a real behavioral
divergence).
Co-authored-by: sim <sim@local>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
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