fix(ext/node): validate fs.watch options.ignore

[nathanwhitbot]

Summary

fs.watch accepted any value for options.ignore and silently dropped invalid input. Node's internal/validators.js (validateIgnoreOption / validateIgnoreOptionElement, called from internal/fs/watchers.js) enforces:

• Element must be string, RegExp, or function — otherwise ERR_INVALID_ARG_TYPE.
• Empty string raises ERR_INVALID_ARG_VALUE ("must be a non-empty string").
• Arrays validate each element; null / undefined are accepted as no-op.

This patch ports those checks into ext/node/polyfills/fs.ts#watch. The actual ignore-matching is still a no-op (a separate piece of work) — the test only covers the validation contract.

Enables parallel/test-fs-watch-ignore-invalid.js.

Test plan

• cargo test --test node_compat -- test-fs-watch-ignore-invalid (was failing on main, passes here)
• cargo build --bin deno clean
• tools/format.js and tools/lint.js --js clean
• Sibling enabled fs.watch tests still pass: test-fs-watch, test-fs-watch-recursive-add-file, test-fs-watch-close-when-destroyed, test-fs-watch-recursive-add-file-with-url, test-fs-watch-recursive-add-file-to-existing-subfolder.

[nathanwhitbot]

1:1 port of Node's validateIgnoreOption + validateIgnoreOptionElement
from lib/internal/validators.js (L580–609). Allowed forms (string,
RegExp, function), the empty-string rejection, and the array-recursion
all match. Locking down fs.watch's contract here is the right move.

Three minor differences vs. upstream — none blocking, flagging for
follow-up:

• Validation order: in Node, validateIgnoreOption runs after
  getValidatedPath(filename) (see lib/internal/fs/watchers.js
  L306–309). This PR runs it before getValidatedPath(filename) in
  watch(), so a call with both an invalid path and an invalid ignore
  surfaces the ignore error first. Tiny user-visible divergence.

• value instanceof RegExp vs Node's isRegExp(value) (the latter
  is Object.prototype.toString.call(...) === '[object RegExp]' and is
  realm-agnostic). A RegExp coming from another realm (e.g., across
  worker_threads/vm contexts) would pass on Node and throw here. Edge
  case, but isRegExp from internal/util/types is already imported
  elsewhere in the file.

• hideStackFrames isn't replicated. Errors thrown from
  validateIgnoreOption will include the validator function in the
  stack trace where Node would point at the user's fs.watch call.
  Minor UX nit; happy to leave as-is unless the test asserts on stack
  shape (it doesn't).

LGTM.

[bartlomieju]

This fails prefer-primordials lint

[fibibot]

The validation logic itself is right — validateIgnoreOption / validateIgnoreOptionElement cleanly mirror Node's lib/internal/validators.js: string-or-RegExp-or-function gets ERR_INVALID_ARG_TYPE, empty string gets ERR_INVALID_ARG_VALUE, array recurses, null/undefined are accepted as no-op. The body's caveat that the actual ignore-matching is still a no-op (separate work) is honest — this PR is just landing the validation contract.

But CI is red on lint across linux/macos/windows debug — prefer-primordials rejects value instanceof RegExp and Array.isArray(value) in the new validators. Inline fix below.

Once lint is green I'll re-confirm.

[fibibot]

LGTM after 65088778. Both prefer-primordials lint hits are fixed exactly as suggested:

• value instanceof RegExp → ObjectPrototypeIsPrototypeOf(RegExpPrototype, value)
• Array.isArray(value) → ArrayIsArray(value)

RegExpPrototype and ArrayIsArray correctly added to the existing primordials destructure. Validation logic and the upstream-Node mapping (validateIgnoreOption / validateIgnoreOptionElement) is unchanged from the prior review.

CI now green on all the relevant areas — lint debug clean across linux/macos/windows, test node_compat debug clean across all four x86_64/aarch64 platforms (windows-aarch64 still pending but the other 5 + windows-x86_64 finished green), test unit_node debug clean on all 6 platforms. Nothing red, no fs.ts-relevant pending blockers.

Body's caveat that the actual ignore-matching is a no-op (separate work) is still accurate — this just lands the validation contract that test-fs-watch-ignore-invalid.js exercises.

[nathanwhitbot]

build release linux-x86_64 fail on run 25032238097 — "Set up incremental LTO and sysroot build" step failed before any build ran. Infra. cc @nathanwhit for a rerun.

[bartlomieju]

@nathanwhit this needs a merge and conflict resolution