1 files changed, 112 insertions, 0 deletions
diff --git a/tools/lint/libpref/__init__.py b/tools/lint/libpref/__init__.py
new file mode 100644
index 0000000000..e986be39d0
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+++ b/tools/lint/libpref/__init__.py
@@ -0,0 +1,112 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import re
+import sys
+
+import yaml
+from mozlint import result
+from mozlint.pathutils import expand_exclusions
+
+# This simple linter checks for duplicates from
+# modules/libpref/init/StaticPrefList.yaml against modules/libpref/init/all.js
+
+# If for any reason a pref needs to appear in both files, add it to this set.
+IGNORE_PREFS = {
+    "devtools.console.stdout.chrome",  # Uses the 'sticky' attribute.
+    "devtools.console.stdout.content",  # Uses the 'sticky' attribute.
+    "fission.autostart",  # Uses the 'locked' attribute.
+    "browser.dom.window.dump.enabled",  # Uses the 'sticky' attribute.
+    "apz.fling_curve_function_y2",  # This pref is a part of a series.
+    "dom.postMessage.sharedArrayBuffer.bypassCOOP_COEP.insecure.enabled",  # NOQA: E501; Uses the 'locked' attribute.
+}
+PATTERN = re.compile(r"\s*pref\(\s*\"(?P<pref>.+)\"\s*,\s*(?P<val>.+)\)\s*;.*")
+
+
+def get_names(pref_list_filename):
+    pref_names = {}
+    # We want to transform patterns like 'foo: @VAR@' into valid yaml. This
+    # pattern does not happen in 'name', so it's fine to ignore these.
+    # We also want to evaluate all branches of #ifdefs for pref names, so we
+    # ignore anything else preprocessor related.
+    file = open(pref_list_filename).read().replace("@", "")
+    try:
+        pref_list = yaml.safe_load(file)
+    except (IOError, ValueError) as e:
+        print("{}: error:\n  {}".format(pref_list_filename, e), file=sys.stderr)
+        sys.exit(1)
+
+    for pref in pref_list:
+        if pref["name"] not in IGNORE_PREFS:
+            pref_names[pref["name"]] = pref["value"]
+
+    return pref_names
+
+
+# Check the names of prefs against each other, and if the pref is a duplicate
+# that has not previously been noted, add that name to the list of errors.
+def check_against(path, pref_names):
+    errors = []
+    prefs = read_prefs(path)
+    for pref in prefs:
+        if pref["name"] in pref_names:
+            errors.extend(check_value_for_pref(pref, pref_names[pref["name"]], path))
+    return errors
+
+
+def check_value_for_pref(some_pref, some_value, path):
+    errors = []
+    if some_pref["value"] == some_value:
+        errors.append(
+            {
+                "path": path,
+                "message": some_pref["raw"],
+                "lineno": some_pref["line"],
+                "hint": "Remove the duplicate pref or add it to IGNORE_PREFS.",
+                "level": "error",
+            }
+        )
+    return errors
+
+
+# The entries in the *.js pref files are regular enough to use simple pattern
+# matching to load in prefs.
+def read_prefs(path):
+    prefs = []
+    with open(path) as source:
+        for lineno, line in enumerate(source, start=1):
+            match = PATTERN.match(line)
+            if match:
+                prefs.append(
+                    {
+                        "name": match.group("pref"),
+                        "value": evaluate_pref(match.group("val")),
+                        "line": lineno,
+                        "raw": line,
+                    }
+                )
+    return prefs
+
+
+def evaluate_pref(value):
+    bools = {"true": True, "false": False}
+    if value in bools:
+        return bools[value]
+    elif value.isdigit():
+        return int(value)
+    return value
+
+
+def checkdupes(paths, config, **kwargs):
+    results = []
+    errors = []
+    pref_names = get_names(config["support-files"][0])
+    files = list(expand_exclusions(paths, config, kwargs["root"]))
+    for file in files:
+        errors.extend(check_against(file, pref_names))
+    for error in errors:
+        results.append(result.from_config(config, **error))
+    return results