lint: Add Prettier as a linter for YAML files.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

package.json

@@ -96,6 +96,7 @@
     "jsdom": "^16.1.0",
     "nyc": "^15.0.0",
     "phantomjs-prebuilt": "^2.1.16",
+    "prettier": "^2.0.5",
     "puppeteer": "^3.0.0",
     "source-map": "^0.6.1",
     "stylelint": "^13.0.0",

tools/lint

@@ -93,6 +93,11 @@ def run() -> None:
     linter_config.external_linter('isort', ['isort'], ['py'],
                                   description="Sorts Python import statements",
                                   check_arg=['--check-only', '--diff'])
+    linter_config.external_linter('prettier', ['node_modules/.bin/prettier'], ['yaml', 'yml'],
+                                  check_arg=['--check'], fix_arg=['--write'],
+                                  description="Formats YAML files",
+                                  # https://github.com/prettier/prettier/pull/8703
+                                  suppress_line=lambda line: line in ["Checking formatting...\n", "All matched files use Prettier code style!\n"])
 
     semgrep_command = ["semgrep", "--config=./tools/semgrep.yml", "--error",
                        # This option is dangerous in the context of running

version.py

@@ -44,4 +44,4 @@ API_FEATURE_LEVEL = 24
 #   historical commits sharing the same major version, in which case a
 #   minor version bump suffices.
 
-PROVISION_VERSION = '89.3'
+PROVISION_VERSION = '89.4'

yarn.lock

@@ -9669,6 +9669,11 @@ prepend-http@^1.0.0:
   resolved "https://registry.yarnpkg.com/prepend-http/-/prepend-http-1.0.4.tgz#d4f4562b0ce3696e41ac52d0e002e57a635dc6dc"
   integrity sha1-1PRWKwzjaW5BrFLQ4ALlemNdxtw=
 
+prettier@^2.0.5:
+  version "2.0.5"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-2.0.5.tgz#d6d56282455243f2f92cc1716692c08aa31522d4"
+  integrity sha512-7PtVymN48hGcO4fGjybyBSIWDsLU4H4XlvOHfq91pz9kkGlonzwTfYkaIEwiRg/dAJF9YlbsduBAgtYLi+8cFg==
+
 pretty-error@^2.1.1:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/pretty-error/-/pretty-error-2.1.1.tgz#5f4f87c8f91e5ae3f3ba87ab4cf5e03b1a17f1a3"