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fix(fs): exists rethrows Deno.errors.PermissionDenied when existence is indeterminate #7170

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fix(fs): exists rethrows Deno.errors.PermissionDenied when existence is indeterminate #7170

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22 changes: 18 additions & 4 deletions fs/exists.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -156,8 +156,15 @@ export async function exists(
(await Deno.permissions.query({ name: "read", path })).state ===
"granted"
) {
// --allow-read not missing
return !options?.isReadable; // PermissionDenied was raised by file system, so the item exists, but can't be read
// --allow-read is not missing, so PermissionDenied came from the
// OS. If the caller specifically asked whether the path is
// readable, "no" is a defensible answer. Otherwise the usual
// cause is that the parent directory isn't traversable and we
// genuinely can't tell whether the path exists — guessing "true"
// silently misleads callers (see #6528). Re-throw so the caller
// can decide how to handle the indeterminate case.
if (options?.isReadable) return false;

@bartlomieju bartlomieju Jun 30, 2026

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The { isReadable: true } path confidently returns false for the exact scenario the default path now treats as indeterminate (parent not traversable → can't even stat, so we can't truly know it's unreadable). Keeping it for backward-compat with the existing exists() returns true for an existing dir symlink test is reasonable, but a one-liner noting this asymmetry is intentional would help future readers.

throw error;
}
}
throw error;
Expand Down Expand Up @@ -294,8 +301,15 @@ export function existsSync(
if (
Deno.permissions.querySync({ name: "read", path }).state === "granted"
) {
// --allow-read not missing
return !options?.isReadable; // PermissionDenied was raised by file system, so the item exists, but can't be read
// --allow-read is not missing, so PermissionDenied came from the
// OS. If the caller specifically asked whether the path is
// readable, "no" is a defensible answer. Otherwise the usual
// cause is that the parent directory isn't traversable and we
// genuinely can't tell whether the path exists — guessing "true"
// silently misleads callers (see #6528). Re-throw so the caller
// can decide how to handle the indeterminate case.
if (options?.isReadable) return false;
throw error;
}
}
throw error;
Expand Down
61 changes: 61 additions & 0 deletions fs/exists_test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -362,3 +362,64 @@ Deno.test("existsSync() returns false when both isDirectory and isFile sets true
await Deno.remove(tempDirPath, { recursive: true });
}
});

// https://github.com/denoland/std/issues/6528 — when --allow-read is granted
// but the OS denies access (typically because the parent directory isn't
// traversable), the previous behavior returned `true` and silently misled
// callers. Now we rethrow Deno.errors.PermissionDenied so callers can decide
// how to handle the indeterminate case. The `isReadable: true` branch is
// unchanged: that question has a definitive answer (not readable → false).
Deno.test(
{
name:
"exists() rethrows Deno.errors.PermissionDenied when the parent is inaccessible (#6528)",
ignore: Deno.build.os === "windows",
},
async function () {
const tempDirPath = await Deno.makeTempDir();
const innerPath = path.join(tempDirPath, "inner");
try {
await Deno.chmod(tempDirPath, 0o000);
let caught: unknown;
try {
await exists(innerPath);
} catch (e) {
caught = e;
}
assert(caught instanceof Deno.errors.PermissionDenied);
Comment on lines +383 to +389

@bartlomieju bartlomieju Jun 30, 2026

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Consider assertRejects here (and assertThrows in the sync test) instead of the manual try/catch + instanceof assert — it's the std convention and reads cleaner:

await assertRejects(
  () => exists(innerPath),
  Deno.errors.PermissionDenied,
);

They'd need adding to the @std/assert import at the top of the file.


// isReadable:true still returns false — that question can be answered.
assertEquals(await exists(innerPath, { isReadable: true }), false);
} finally {
await Deno.chmod(tempDirPath, 0o755);
await Deno.remove(tempDirPath, { recursive: true });
}
},
);

Deno.test(
{
name:
"existsSync() rethrows Deno.errors.PermissionDenied when the parent is inaccessible (#6528)",
ignore: Deno.build.os === "windows",
},
function () {
const tempDirPath = Deno.makeTempDirSync();
const innerPath = path.join(tempDirPath, "inner");
try {
Deno.chmodSync(tempDirPath, 0o000);
let caught: unknown;
try {
existsSync(innerPath);
} catch (e) {
caught = e;
}
assert(caught instanceof Deno.errors.PermissionDenied);

assertEquals(existsSync(innerPath, { isReadable: true }), false);
} finally {
Deno.chmodSync(tempDirPath, 0o755);
Deno.removeSync(tempDirPath, { recursive: true });
}
},
);
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