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fix: keep surrogate pairs whole when truncating file names #148

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Merged
jerelvelarde merged 2 commits into from
Oct 6, 2026
Merged

fix: keep surrogate pairs whole when truncating file names #148

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9012964
fix: keep surrogate pairs whole when truncating file names
Mrdifferent2022 Oct 6, 2026
c7aa468
Merge branch 'main' into fix/sanitize-filename-surrogate
jerelvelarde Oct 6, 2026
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5 changes: 3 additions & 2 deletions apps/server/src/files.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,11 @@ const FILE_ID = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-

export function sanitizeFileName(name: string): string {
const base = name.split(/[\\/]/).at(-1) ?? "document.pdf";
// Slice code points, not UTF-16 units, so a surrogate pair is never split in half.
const cleaned = Array.from(base)
.filter((character) => character.charCodeAt(0) >= 32 && character.charCodeAt(0) !== 127)
.join("")
.slice(0, 180);
.slice(0, 180)
.join("");
return cleaned || "document.pdf";
}

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5 changes: 5 additions & 0 deletions tests/resource-ids.test.ts
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Expand Up @@ -53,6 +53,11 @@ test("file names never collapse to an empty display name", () => {
const long = sanitizeFileName(`${"a".repeat(300)}.pdf`);
assert.ok(long.length <= 180);
assert.ok(long.length > 0);
// The 180-character bound slices whole code points, never half a surrogate pair.
const emoji = sanitizeFileName(`${"x".repeat(179)}😀.pdf`);
assert.equal(emoji, `${"x".repeat(179)}😀`);
assert.equal([...emoji].length, 180);
assert.equal([...sanitizeFileName(`${"x".repeat(180)}😀.pdf`)].length, 180);
});

test("file lookups reject malformed IDs instead of probing storage", async (t) => {
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