The Windows coverage gate reported changed-code coverage at 99.9360% because
drive_push.go:471-473 — the branch that surfaces an error passed to the
fs.WalkDir callback as its third argument — was not exercised. macOS runners
happen to exercise it via directory-lstat failures, Windows runners do not.
Add walk_callback_receives_error under
TestCrossPlatformCoverageDrivePushFinalWalkAndCommandGates, which swaps
walkPinnedLocalFS to invoke the callback with a non-nil err and asserts the
error is bubbled up unchanged.
Verified locally that the new subtest hits drive_push.go:471.17,473.4 with
count=1.
Windows keeps the pinned directory locked while a handle inside it is open
(os.Root plus the pull temp file or the upload source), so renaming that
directory fails with a sharing violation. Every "pinned root/ancestor was
swapped" reproduction in the drive mirror tests relied on such a rename, so 13
tests failed on windows-latest. That, not a coverage shortfall, is why
Coverage (Windows) exited 1 before the gate ever ran.
Each reproduction now falls back to injecting the equivalent identity change
when the rename is refused. pinnedPullRoot.verify() and verifyParent() read
current identity only through pullPathStat / pullRootLstat, so pointing those
seams at another directory hits the same fail-closed branches. Unix still
performs the real move and loses no strength.
Assertions that need an actual replacement tree now branch on the helper's
return value. forcePinnedFallbackForTest makes the fallback path itself
regressible on any platform, and a dedicated test covers it.
Verified locally with the fallback forced on: all 13 tests pass and changed
code coverage stays at 100%.
The platform coverage gate runs only TestAllShortcuts and
TestCrossPlatformCoverage*, so several changed statements had no platform
test exercising them:
- drive_pull.go: the smart-policy re-check that skips publication when the
target is refreshed in place (same inode) while the download is running.
- drive_pull.go: the post-publish verifyParent failure, where the result is
already on disk and must not be rolled back.
- drive_replace_unix.go: rename(2) replacement of an existing target; the
Windows side already had the symmetric test.
- drive_status_windows.go: the filepath.Clean rewrite guard had no input
reaching it, because isSafeRemoteSegment filters separators upstream.
macOS changed-code coverage: 99.8053% -> 100.0000% (1541 statements).
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