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https://github.com/lukaszraczylo/filepuff-mcp.git
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lukaszraczylo
3195e353e2
firstLineOf (query) and truncateString (edit) sliced strings at a raw byte offset, splitting a multibyte UTF-8 character into invalid bytes in LLM-facing output (ast_query compact format and edit not-found errors are hot paths). Extract the rune-boundary backoff already used by search's truncateLine into util.RuneBoundary and route all three sites through it. Adds table-driven tests for the primitive and a multibyte case for firstLineOf.
38 lines
1.0 KiB
Go
38 lines
1.0 KiB
Go
package util
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import (
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"testing"
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"unicode/utf8"
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)
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func TestRuneBoundary(t *testing.T) {
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// "café" — 'é' is 2 bytes (0xC3 0xA9), occupying indices 3,4. len == 5.
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const cafe = "café"
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cases := []struct {
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name string
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s string
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i int
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want int
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}{
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{"negative clamps to zero", "abc", -1, 0},
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{"zero", "abc", 0, 0},
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{"beyond length clamps to len", "abc", 99, 3},
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{"ascii exact boundary", "abcdef", 4, 4},
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{"inside multibyte backs off", cafe, 4, 3}, // index 4 is the 2nd byte of 'é'
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{"on multibyte start stays", cafe, 3, 3}, // index 3 is the 1st byte of 'é'
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{"end of multibyte string", cafe, 5, 5}, // len == 5, clamped path
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}
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for _, c := range cases {
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t.Run(c.name, func(t *testing.T) {
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got := RuneBoundary(c.s, c.i)
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if got != c.want {
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t.Fatalf("RuneBoundary(%q, %d) = %d, want %d", c.s, c.i, got, c.want)
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}
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// Invariant: the prefix is always valid UTF-8.
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if !utf8.ValidString(c.s[:got]) {
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t.Fatalf("RuneBoundary(%q, %d) sliced invalid UTF-8: %q", c.s, c.i, c.s[:got])
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}
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})
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}
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}
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