lint: Use --groups to specify specific groups to run.

This helps generalize the use of groups inside zulint.
Introduce list_files to return `by_lang` files dict.
Add feature to create custom groups.
Make custom groups for backend and frontend files.

tools/ci/backend

@@ -6,7 +6,7 @@ echo "Test suite is running under $(python --version)."
 set -e
 set -x
 
-./tools/lint --backend --skip=gitlint,mypy  # gitlint disabled because flaky
+./tools/lint --groups=backend --skip=gitlint,mypy  # gitlint disabled because flaky
 ./tools/test-tools
 # We need to pass a parallel level to test-backend because CircleCI's
 # docker setup means the auto-detection logic sees the ~36 processes

tools/ci/frontend

@@ -5,7 +5,7 @@ source tools/ci/activate-venv
 set -e
 set -x
 
-./tools/lint --frontend --skip=gitlint  # gitlint disabled because flaky
+./tools/lint --groups=frontend --skip=gitlint  # gitlint disabled because flaky
 
 # Run the node tests first, since they're fast and deterministic
 ./tools/test-js-with-node --coverage

tools/lint

@@ -10,9 +10,7 @@ from lib import sanity_check
 sanity_check.check_venv(__file__)
 
 from linter_lib.custom_check import python_rules, non_py_rules
-from zulint import lister
 from zulint.command import add_default_linter_arguments, LinterConfig
-from typing import cast, Dict, List
 import random
 
 def run():
@@ -24,13 +22,6 @@ def run():
     parser.add_argument('--full',
                         action='store_true',
                         help='Check some things we typically ignore')
-    limited_tests_group = parser.add_mutually_exclusive_group()
-    limited_tests_group.add_argument('--frontend',
-                                     action='store_true',
-                                     help='Only check files relevant to frontend')
-    limited_tests_group.add_argument('--backend',
-                                     action='store_true',
-                                     help='Only check files relevant to backend')
     add_default_linter_arguments(parser)
     args = parser.parse_args()
 
@@ -50,23 +41,16 @@ def run():
 
     assert_provisioning_status_ok(args.force)
 
-    backend_file_types = ['py', 'sh', 'pp', 'json', 'md', 'txt', 'text', 'yaml', 'rst']
-    frontend_file_types = ['js', 'ts', 'css', 'scss', 'handlebars', 'html']
-    file_types = backend_file_types + frontend_file_types
-    if args.backend:
-        file_types = backend_file_types
-    if args.frontend:
-        file_types = frontend_file_types
-
-    by_lang = cast(Dict[str, List[str]],
-                   lister.list_files(args.targets, modified_only=args.modified,
-                                     ftypes=file_types,
-                                     use_shebang=True, group_by_ftype=True, exclude=EXCLUDED_FILES))
-
     # Invoke the appropriate lint checker for each language,
     # and also check files for extra whitespace.
 
-    linter_config = LinterConfig(args, by_lang)
+    linter_config = LinterConfig(args)
+
+    by_lang = linter_config.list_files(groups={
+        'backend': ['py', 'sh', 'pp', 'json', 'md', 'txt', 'text', 'yaml', 'rst'],
+        'frontend': ['js', 'ts', 'css', 'scss', 'handlebars', 'html'],
+    }, exclude=EXCLUDED_FILES)
+
     linter_config.external_linter('add_class', ['tools/find-add-class'], ['js'])
     linter_config.external_linter('css', ['node', 'node_modules/.bin/stylelint'], ['css', 'scss'])
     linter_config.external_linter('eslint', ['node', 'node_modules/.bin/eslint',

tools/test-all

@@ -39,7 +39,7 @@ run ./tools/check-provision $FORCEARG
 run ./tools/clean-repo
 
 # ci/backend
-run ./tools/lint --backend $FORCEARG
+run ./tools/lint --groups=backend $FORCEARG
 run ./tools/test-tools
 run ./tools/test-backend --include-webhooks $FORCEARG
 run ./tools/test-migrations
@@ -57,7 +57,7 @@ run ./tools/test-api
 # run ./tools/test-queue-worker-reload
 
 # ci/frontend
-run ./tools/lint --frontend $FORCEARG
+run ./tools/lint --groups=frontend $FORCEARG
 run ./tools/test-js-with-node
 run ./manage.py makemessages --locale en
 run env PYTHONWARNINGS=ignore ./tools/check-capitalization --no-generate

tools/zulint/README.md

@@ -60,8 +60,8 @@ script with at least the following options:
 
 ```
 (zulip-py3-venv) tabbott@coset:~/zulip$ ./tools/lint --help
-usage: lint [-h] [--force] [--full] [--frontend | --backend] [--modified]
+usage: lint [-h] [--force] [--full] [--modified] [--verbose-timing]
-            [--verbose-timing] [--skip SKIP] [--only ONLY] [--list]
+            [--skip SKIP] [--only ONLY] [--list] [--groups GROUPS]
             [targets [targets ...]]
 
 positional arguments:
@@ -76,6 +76,9 @@ optional arguments:
   --skip SKIP           Specify linters to skip, eg: --skip=mypy,gitlint
   --only ONLY           Specify linters to run, eg: --only=mypy,gitlint
   --list, -l            List all the registered linters
+  --groups GROUPS, -g GROUPS
+                        Only run linter for languages in the group(s), e.g.:
+                        --groups=backend,other_group
 ```
 
 ### pre-commit hook mode

tools/zulint/command.py

@@ -11,9 +11,10 @@ import sys
 
 if False:
     # See https://zulip.readthedocs.io/en/latest/testing/mypy.html#mypy-in-production-scripts
-    from typing import Any, Callable, Dict, List
+    from typing import Callable, Dict, List
 
 from zulint.printer import print_err, colors
+from zulint import lister
 
 def add_default_linter_arguments(parser):
     # type: (argparse.ArgumentParser) -> None
@@ -37,6 +38,11 @@ def add_default_linter_arguments(parser):
     parser.add_argument('--list', '-l',
                         action='store_true',
                         help='List all the registered linters')
+    parser.add_argument('--groups', '-g',
+                        default=[],
+                        type=split_arg_into_list,
+                        help='Only run linter for languages in the group(s), e.g.: '
+                        '--groups=backend,frontend')
 
 def split_arg_into_list(arg):
     # type: (str) -> List[str]
@@ -66,10 +72,24 @@ def run_parallel(lint_functions):
 class LinterConfig:
     lint_functions = {}  # type: Dict[str, Callable[[], int]]
 
-    def __init__(self, args, by_lang):
+    def __init__(self, args):
-        # type: (argparse.Namespace, Any) -> None
+        # type: (argparse.Namespace) -> None
         self.args = args
-        self.by_lang = by_lang  # type: Dict[str, List[str]]
+        self.by_lang = {}  # type: Dict[str, List[str]]
+
+    def list_files(self, file_types=[], groups={}, use_shebang=True, group_by_ftype=True, exclude=[]):
+        # type: (List[str], Dict[str, List[str]], bool, bool, List[str]) -> Dict[str, List[str]]
+        assert file_types or groups, "Atleast one of `file_types` or `groups` must be specified."
+
+        if self.args.groups:
+            file_types = [ft for group in self.args.groups for ft in groups[group]]
+        else:
+            file_types.extend({ft for group in groups.values() for ft in group})
+
+        self.by_lang = lister.list_files(self.args.targets, modified_only=self.args.modified,
+                                         ftypes=file_types, use_shebang=use_shebang,
+                                         group_by_ftype=group_by_ftype, exclude=exclude)
+        return self.by_lang
 
     def lint(self, func):
         # type: (Callable[[], int]) -> Callable[[], int]