What causes "Build dir missing." in gorhill/uBlock?

Invoke as `python tools/make-chromium-meta.py ` where holds the built manifest.json.

gorhill/uBlock · error · SystemExit

Build dir missing.

Error message

Build dir missing.

What it means

make-chromium-meta.py is a build-time post-processor for the Chromium manifest. It requires exactly one CLI argument: the build directory that contains manifest.json (opened at lines 19-21). If argv has no argument or an empty-string argument it aborts via SystemExit before any work (lines 8-9), because there is no build directory to read from or write back to.

Source

Thrown at tools/make-chromium-meta.py:9

#!/usr/bin/env python3

import os
import json
import re
import sys

if len(sys.argv) == 1 or not sys.argv[1]:
    raise SystemExit('Build dir missing.')

proj_dir = os.path.join(os.path.split(os.path.abspath(__file__))[0], '..')
build_dir = os.path.abspath(sys.argv[1])

version = ''
with open(os.path.join(proj_dir, 'dist', 'version')) as f:
    version = f.read().strip()

manifest_out = {}
manifest_out_file = os.path.join(build_dir, 'manifest.json')
with open(manifest_out_file) as f:
    manifest_out = json.load(f)

manifest_out['version'] = version

# Development build? If so, modify name accordingly.
match = re.search(r'^\d+\.\d+\.\d+\.\d+$', version)
if match:

View on GitHub (pinned to c68df492fd)

Solutions

Invoke as `python tools/make-chromium-meta.py <build_dir>` where <build_dir> holds the built manifest.json.
Run through the project's normal build tooling (npm scripts) which supplies the argument correctly.
If wrapping the script, assert the build-dir argument is non-empty before invoking it.

Example fix

# before
python tools/make-chromium-meta.py        # SystemExit: Build dir missing.

# after
python tools/make-chromium-meta.py build/chromium

Defensive patterns

Strategy: validation

Validate before calling

import sys
if len(sys.argv) < 2 or not sys.argv[1].strip():
    raise SystemExit('Usage: make-chromium-meta.py <build_dir>')
build_dir = sys.argv[1]

Prevention

Pass the build output directory as the first argument every time.
Invoke through the project's npm scripts rather than running the .py directly.
If wrapping the script, fail fast with a clear usage message when the arg is missing.
Verify the manifest.json exists under the given build dir before proceeding.

When it happens

Trigger: Running `python tools/make-chromium-meta.py` with no argument, or with an empty-string argument. Invoking it through a wrapper or make target whose build-dir variable was left unset or expanded to empty.

Common situations: Running the script manually during local packaging without passing the build output dir; a Makefile/npm script with an empty $(BUILD_DIR) placeholder; copy-pasting the command and dropping the trailing path argument.

Related errors

AI-assisted analysis of gorhill/uBlock@c68df492fd (2026-08-12). Data as JSON: /api/errors/e6fc94098867be4a. Report an issue: GitHub.