fix: std.format specialize arg swap and %-0 flag interaction#1045
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fix: std.format specialize arg swap and %-0 flag interaction#1045He-Pin wants to merge 1 commit into
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Motivation:
Two bugs found via adversarial testing against go-jsonnet, jrsonnet,
and Python's % operator:
1. std.format("%d", "abc") reported misleading "too many values to
format: 1, expected 0" instead of a type error. Root cause: the
specialize() method in Format_ swapped the format string and values
arguments when the values happened to be a string literal.
2. %-05d applied zero-padding instead of left-justification. Per
POSIX/Python convention, when both - (left-justify) and 0 (zero-pad)
flags are present, - takes precedence and 0 is ignored.
Modification:
1. Fix specialize() pattern to correctly use the first argument (format
string) as the PartialApplyFmt template, not the second argument
(values). Changed `Array(str, fmt: Val.Str)` to
`Array(fmtStr: Val.Str, vals)`.
2. Add `&& !formatted.leftAdjusted` to the zero-padding conditions in
Format.widen(), so left-justify takes precedence over zero-pad.
Result:
- std.format("%d", "abc") now correctly reports "expected number at
position 0, got string", matching go-jsonnet and jrsonnet.
- %-05d now produces "42 " (left-justified) instead of "00042"
(zero-padded), matching go-jsonnet, jrsonnet, and Python.
- %05d (zero-pad without left-justify) still works correctly.
- All tests pass on JVM 2.12, 2.13, 3.3.
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Motivation
Two
std.formatbugs found via adversarial testing against go-jsonnet, jrsonnet, and Python's%operator:std.format("%d", "abc")reported misleading"too many values to format: 1, expected 0"instead of a type error. Root cause: thespecialize()method inFormat_swapped the format string and values arguments when the values happened to be a string literal.%-05dapplied zero-padding instead of left-justification. Per POSIX/Python convention, when both-(left-justify) and0(zero-pad) flags are present,-takes precedence.std.format("%d", "abc")too many values...Format required number...type error...TypeErrorexpected number...✅std.format("%-05d", 42)"00042""42 ""42 ""42 ""42 "✅std.format("%-05d", -42)"-0042""-42 ""-42 ""-42 ""-42 "✅Modification
StringModule.scala: Fixspecialize()pattern to correctly use the first argument (format string) as thePartialApplyFmttemplate. ChangedArray(str, fmt: Val.Str)toArray(fmtStr: Val.Str, vals).Format.scala: Add&& !formatted.leftAdjustedto zero-padding conditions inwiden(), so left-justify takes precedence over zero-pad.Result
std.format("%d", "abc")correctly reports type error.%-05dproduces"42 "(left-justified), matching go-jsonnet, jrsonnet, and Python.%05d(zero-pad only) still produces"00042"correctly.