lint: Add --fix option to ./tools/lint.

Linters with the fix option are stylelint, eslint and puppet-lint.

tools/lint

@@ -22,6 +22,9 @@ def run():
     parser.add_argument('--full',
                         action='store_true',
                         help='Check some things we typically ignore')
+    parser.add_argument('--fix',
+                        action='store_true',
+                        help='Automatically fix problems where supported')
     add_default_linter_arguments(parser)
     args = parser.parse_args()
 
@@ -54,10 +57,12 @@ def run():
     linter_config.external_linter('add_class', ['tools/find-add-class'], ['js'],
                                   description="Compares addClass() between JavaSsript and CSS.")
     linter_config.external_linter('css', ['node', 'node_modules/.bin/stylelint'], ['css', 'scss'],
+                                  fix_arg='--fix',
                                   description="Standard CSS style and formatting linter "
                                   "(config: .stylelintrc)")
     linter_config.external_linter('eslint', ['node', 'node_modules/.bin/eslint',
                                              '--quiet', '--cache', '--ext', '.js,.ts'], ['js', 'ts'],
+                                  fix_arg='--fix',
                                   description="Standard JavaScript style and formatting linter"
                                   "(config: .eslintrc).")
     linter_config.external_linter('puppet', ['puppet', 'parser', 'validate'], ['pp'],
@@ -65,6 +70,7 @@ def run():
                                   "checking for syntax errors.")
     linter_config.external_linter('puppet-lint',
                                   ['puppet-lint'] + PUPPET_CHECK_RULES_TO_EXCLUDE, ['pp'],
+                                  fix_arg='--fix',
                                   description="Standard puppet linter"
                                   "(config: tools/linter_lib/exclude.py)")
     linter_config.external_linter('templates', ['tools/check-templates'], ['handlebars', 'html'],

tools/zulint/command.py

@@ -11,7 +11,7 @@ import sys
 
 if False:
     # See https://zulip.readthedocs.io/en/latest/testing/mypy.html#mypy-in-production-scripts
-    from typing import Callable, Dict, List
+    from typing import Callable, Dict, List, Optional
 
 from zulint.printer import print_err, colors, BOLDRED, BLUE, GREEN, ENDC
 from zulint import lister
@@ -101,9 +101,9 @@ class LinterConfig:
         self.lint_descriptions[func.__name__] = func.__doc__ if func.__doc__ else "External Linter"
         return func
 
-    def external_linter(self, name, command, target_langs=[], pass_targets=True,
+    def external_linter(self, name, command, target_langs=[], pass_targets=True, fix_arg=None,
                         description="External Linter"):
-        # type: (str, List[str], List[str], bool, str) -> None
+        # type: (str, List[str], List[str], bool, Optional[str], str) -> None
         """Registers an external linter program to be run as part of the
         linter.  This program will be passed the subset of files being
         linted that have extensions in target_langs.  If there are no
@@ -126,6 +126,9 @@ class LinterConfig:
                     # invoking the external linter.
                     return 0
 
+            if self.args.fix and fix_arg:
+                command.append(fix_arg)
+
             if pass_targets:
                 full_command = command + targets
             else: