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fix: empty string causes panic #1

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Merged
galactixx merged 2 commits into from
Nov 9, 2025
Merged

fix: empty string causes panic #1

galactixx merged 2 commits into from
Nov 9, 2025

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@rm-hull
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@rm-hull rm-hull commented Nov 8, 2025 •
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At the moment, if I pass an empty string as per the added test case, then the stringwrap function panics:

$ go test ./...
--- FAIL: TestStringWrap (0.00s)
    --- FAIL: TestStringWrap/Wrapped_String_Test_15 (0.00s)
panic: runtime error: index out of range [-1] [recovered, repanicked]

goroutine 37 [running]:
testing.tRunner.func1.2({0x10249e600, 0x140000b8690})
        /opt/homebrew/Cellar/go/1.25.4/libexec/src/testing/testing.go:1872 +0x190
testing.tRunner.func1()
        /opt/homebrew/Cellar/go/1.25.4/libexec/src/testing/testing.go:1875 +0x31c
panic({0x10249e600?, 0x140000b8690?})
        /opt/homebrew/Cellar/go/1.25.4/libexec/src/runtime/panic.go:783 +0x120
github.com/galactixx/stringwrap.(*WrappedStringSeq).lastWrappedLine(...)
        /Users/rhu/dev/stringwrap/stringwrap.go:92
github.com/galactixx/stringwrap.stringWrap({0x102445868, 0x0}, 0x5, 0x4, 0x1, 0x1)
        /Users/rhu/dev/stringwrap/stringwrap.go:491 +0x548
github.com/galactixx/stringwrap.StringWrapSplit(...)
        /Users/rhu/dev/stringwrap/stringwrap.go:542
github.com/galactixx/stringwrap.wrapString({{0x102445868, 0x0}, {0x102445868, 0x0}, 0x5, 0x1, 0x1})
        /Users/rhu/dev/stringwrap/stringwrap_test.go:25 +0x48
github.com/galactixx/stringwrap.TestStringWrap.func1(0x14000139180)
        /Users/rhu/dev/stringwrap/stringwrap_test.go:143 +0x40
testing.tRunner(0x14000139180, 0x1400008eef0)
        /opt/homebrew/Cellar/go/1.25.4/libexec/src/testing/testing.go:1934 +0xc8
created by testing.(*T).Run in goroutine 22
        /opt/homebrew/Cellar/go/1.25.4/libexec/src/testing/testing.go:1997 +0x364
FAIL    github.com/galactixx/stringwrap 0.466s
FAIL

This PR adds a test case to TestStringWrap to reproduce the panic.

edit: LMK if you'd like me to provide a fix & i'll add further commits to this PR I've pushed a second commit fixing the issue.

@rm-hull
test: Test empty string input handling
aaa46b5 
Adds a test case to `TestStringWrap` to verify that an empty
string input correctly yields an empty string output.
@rm-hull
fix: sidestep panic accessing last wrapped line of empty sequence
4b4b23f 
The function `lastWrappedLine` is updated to safely return `nil`
if the internal sequence of wrapped lines is empty, avoiding
a runtime panic (index out of bounds).

The main wrapping logic now checks for a `nil` return before
accessing the line properties.

Testing logic for zero-length wrapped strings was also fixed
to correctly assert line counts for empty output.
@rm-hull rm-hull changed the title [WIP] bugfix: empty string causes panic fix: empty string causes panic Nov 8, 2025
@galactixx
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galactixx commented Nov 9, 2025

this is great. thanks

@galactixx galactixx merged commit 4c1b8d4 into galactixx:main Nov 9, 2025
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@rm-hull @galactixx