CI: Lint starlark files with buildifier (#59157)

* Add verify-starlark build action that returns an error for starlark files with lint

Relies on `buildifier` tool.

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Add verify_starlark_step to PR pipeline

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Manually fetch buildifier in curl_image until a new build_image is created

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Format with buildifier

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Remove all unused variables retaining one unused function

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Use snake_case for variable

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Replace deprecated dictionary concatenation with .update() method

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Start adding docstrings for all modules and functions

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Prefer os.WriteFile as ioutil.WriteFile has been deprecated since go 1.16

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Attempt to document the behavior of the init_enterprise_step

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document test_backend pipeline

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document enterprise_downstream_step

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document the pipeline utility function

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document publish_images_step

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document publish_images_steps

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document enterprise2_pipelines function

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Add tags table for Starlark files.

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document test_frontend

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document windows function

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Add docstrings to verifystarlark functions

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Refactor error handling to be more clear and document complex behavior

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Split errors into execution errors and verification errors

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document all other library functions

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Add local variables to TAGS

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Add blank line between all Args and Returns sections

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Fix new linting errors

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Lint new Starlark files

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Correct buildifier binary mv

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Document the need to set nofile ulimit to at least 2048

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Update build-container to include buildifier

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Ensure buildifier binary is executable

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Fix valid content test

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Simply return execution error

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Only check files rather than fixing them

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Use updated build-container with executable buildifier

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Test that context cancellation stops execution

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Simplify error handling

Return execution errors that short circuit WalkDir rather than
separately tracking that error.

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Remove fetching of buildifier binary now that it is in the build-container

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Use build image in verify-starlark step

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Use semver tag

The image is the same but uses a semver tag to make it clearer that
this is a forward upgrade from the old version.

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

* Use node 18 image with buildifier

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

---------

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

scripts/drone/pipelines/lint_frontend.star

@@ -1,18 +1,29 @@
-load(
-    'scripts/drone/steps/lib.star',
-    'identify_runner_step',
-    'yarn_install_step',
-    'lint_frontend_step',
-)
+"""
+This module returns the pipeline used for linting frontend code.
+"""
 
 load(
-    'scripts/drone/utils/utils.star',
-    'pipeline',
+    "scripts/drone/steps/lib.star",
+    "identify_runner_step",
+    "lint_frontend_step",
+    "yarn_install_step",
+)
+load(
+    "scripts/drone/utils/utils.star",
+    "pipeline",
 )
-
 
 def lint_frontend_pipeline(trigger, ver_mode):
-    environment = {'EDITION': 'oss'}
+    """Generates the pipelines used linting frontend code.
+
+    Args:
+      trigger: controls which events can trigger the pipeline execution.
+      ver_mode: used in the naming of the pipeline.
+
+    Returns:
+      Drone pipeline.
+    """
+    environment = {"EDITION": "oss"}
 
     init_steps = [
         identify_runner_step(),
@@ -24,10 +35,10 @@ def lint_frontend_pipeline(trigger, ver_mode):
     ]
 
     return pipeline(
-        name='{}-lint-frontend'.format(ver_mode),
-        edition="oss",
-        trigger=trigger,
-        services=[],
-        steps=init_steps + test_steps,
-        environment=environment,
+        name = "{}-lint-frontend".format(ver_mode),
+        edition = "oss",
+        trigger = trigger,
+        services = [],
+        steps = init_steps + test_steps,
+        environment = environment,
     )