perf(assert): fork-free arg join in core string assertions#846
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The core string assertions joined their haystack args with a
command-substitution fork ($(printf '%s\n' "${arr[@]}")) on every call.
Introduce bashunit::assert::join_to_slot, a fork-free return-slot helper that
joins with newlines and strips trailing newlines, exactly mirroring the old
subshell output. Wired into assert_contains/not_contains, assert_matches/
not_matches and assert_string_starts_with/ends_with (+negations) — 7 sites.
Join step ~35x faster (10.6s -> 0.3s over 20k iterations) and one fewer fork
per assertion, with identical behaviour. assert_line_count is intentionally
left on the subshell (line-count logic depends on that exact form).
Characterization tests pin the preserved contract: trailing newlines ignored,
internal newlines preserved, multi-arg haystacks joined with newlines.
Closes #844
Claude-Session: https://claude.ai/code/session_01JSeB8UzLCpqst55hAK6dED
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🤔 Background
Related #844
The core string assertions forked a subshell (
$(printf '%s\n' "${arr[@]}")) on every call just to join their haystack arguments. Multiplied across thousands of assertions, that fork is the dominant per-assertion cost.💡 Changes
bashunit::assert::join_to_slot, a fork-free return-slot join that mirrors the old subshell exactly (newline-join + strip trailing newlines).assert_contains/assert_not_contains,assert_matches/assert_not_matches,assert_string_starts_with/assert_string_ends_withand their negations (7 sites). Join step ~35× faster (10.6s → 0.3s / 20k iters), one fewer fork per call, identical behaviour.assert_line_countintentionally keeps the subshell — its line-count logic depends on that exact form (noted in perf(assert): remove per-assertion array-join fork in assert.sh #844).Sibling issue #845 (lowercase forks in
assert_contains_ignore_case) was investigated and closed with benchmark evidence — herestring measured marginally slower and combining operands is unsafe for multiline data.https://claude.ai/code/session_01JSeB8UzLCpqst55hAK6dED