[Repo Assist] [JS/TS] Fix sprintf %g/%G not stripping trailing zeros when explicit precision is given#4543
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When using an explicit precision like `sprintf "%.6g" 5.`, the output was "5.00000" instead of the expected "5". The C printf %g format always strips trailing zeros from the mantissa. Also fix the G format in String.format() to correctly handle scientific notation (e.g. "1.0000e-10" -> "1e-10") by using regex substitution before the trimEnd calls. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Rejecting because the fix is not working and invalid. Can be revisited in a new PR by a human later. |
MangelMaxime
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June 26, 2026 09:10
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Summary
sprintf "%.6g" 5.was emitting"5.00000"instead of"5". The Cprintf%gformat (which F#sprintf %gfollows) always strips trailing zeros from the mantissa.Root Cause
In
formatReplacement()(the printf handler), the%g/%Gcase calledtoPrecision(rep, precision)but didn't apply any trailing-zero stripping — unlike theString.format()handler ({0:G}style) at line 393, which already hadtrimEnd(trimEnd(rep, "0"), ".").The bug only affects
%gwith an explicit precision (e.g.%.6g,%.10g). Without an explicit precision,toPrecision()with no argument calls JS.toPrecision(undefined)which is equivalent to.toString()and doesn't pad.Fix
Added trailing-zero stripping to the
%g/%Gcase informatReplacement(), using a regex to correctly handle scientific-notation output (e.g."1.0000e-10"→"1e-10") before thetrimEndpass.Also improved the existing
String.format()G case to use the same regex-first approach, removing the staleTODOcomment.Test
Added
testCase "sprintf %g strips trailing zeros"totests/Js/Main/StringTests.fscovering:sprintf "%.6g" 5. = "5"(was"5.00000")sprintf "%.10g" 1.23 = "1.23"(was"1.2300000000")sprintf "%.6g" 0.0001 = "0.0001"sprintf "%g" 123.456 = "123.456"(no precision — unchanged)sprintf "%.4g" 1234.5 = "1234"