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endsWith, startsWith and indexOf find an empty search string - #24
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Each began with `if (!searchString)`, a null check written as a
truthiness test. While the compiler took "" as true it let "" through,
and the functions went on to give what JavaScript gives: endsWith("")
and startsWith("") true, indexOf("") the position. With "" falsy
(TypeScriptCompiler #509) the guard returned false / -1 for it.
The guards are now `searchString == null`, which is the same test under
either compiler, so this can land before or after the compiler change.
lastIndexOf has the same guard, but it already returns `position` for
"" a few lines later, so it is left alone.
tests/string_empty_search.ts asserts each case. With the compiler fix
and the old guards, it fails at endsWith('').
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Paired with ASDAlexander77/TypeScriptCompiler#511, which makes an empty string falsy (TypeScriptCompiler #509).
endsWith,startsWithandindexOfeach began withif (!searchString), a null check written as a truthiness test. While the compiler took""as true,""passed the guard and the functions gave what JavaScript gives:endsWith("")andstartsWith("")true,indexOf("")the position. With the compiler change, the guard returnedfalse/-1for""instead.The guards are now
searchString == null. That is the same test under either compiler, so this PR can merge before or after the compiler one.lastIndexOfhas the same guard, but a few lines later it already returnspositionfor"", so it is left alone.Test
tests/string_empty_search.tsassertsendsWith,startsWith,indexOf,lastIndexOfandincludeswith"", on a non-empty string and on"".Built locally (release, gc) with the #511 compiler and run with a release-only copy of
tests.ps1: release compile 160/160, release jit 160/160. The debug library was not built.With the #511 compiler and this repo's main
lib.ts, the new test fails withassertion failed: endsWith('').tests/string_indexOf.tsprintsindexOf("")results without asserting them, so it would print-1without failing.🤖 Generated with Claude Code