perf(runner): resolve a test's source location only when needed - #1356
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Every test forked a subshell to read its own definition line:
`$(shopt -s extdebug; declare -F "$fn")`, 1.08ms per call on macOS
arm64 (bash 3.2.57). It produced `<file>:<line>` for a failure message
most tests never emit, and for a report row that add_test discards
before reading when no report is configured. A 500-test file spent
0.35s of 2.75s on it.
Carry the file and function name instead and resolve on the two paths
that render the location. A plain run pays nothing; a run with
`--report-*` pays what it paid before.
The two obvious alternatives are both worse on Bash 3.2, so they are
recorded here rather than retried: a parallel-array map scanned per
test made a 500-test file 7.5ms/test against 6.3ms, because a Bash 3
array is a linked list and indexing is O(i); a single-string map read
with `${map#*$'\n'$fn$'\t'}` made it 19ms/test, because prefix removal
against a leading `*` is quadratic in the string length.
The inputs are not exported. Every consumer runs in a fork, which
inherits them regardless, while an exec'd process gets a function name
its own shell never defined -- which is how a standalone `bashunit -a
assert_same` came to print the location of whichever test had launched
it. It now prints none, and the acceptance snapshot that pinned the
leak loses that line.
perf-fork-budget.md's 0.46ms figure for a bare `$( )` predates arm64
and read as "a subshell is not worth removing"; it now carries the
arm64 numbers.
Closes #1346
Claude-Session: https://claude.ai/code/session_01EXYWTGLjf7qM8Ru3GakDRm
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🤔 Background
Related #1346
Every test forked a subshell to read its own definition line, building a
<file>:<line>that only a failure message and a report row ever read. On macOS arm64 (bash 3.2.57) that is 1.08ms per test.💡 Changes
--report-*run pays what it did before. A 500-test file went from 2.75s to 2.40s.${var#*pat}is quadratic).bashunit assert …therefore stops reporting the location of whichever test launched it — one acceptance snapshot pinned that leak and loses the line.$( )predates arm64, where the same measurement is 1.1-1.4ms.https://claude.ai/code/session_01EXYWTGLjf7qM8Ru3GakDRm