ci: add Helm diff step

Author: khuedoan

.woodpecker/helm-diff.yaml

@@ -0,0 +1,20 @@
+when:
+  branch: ${CI_REPO_DEFAULT_BRANCH}
+
+matrix:
+  STACK:
+    - system
+    - platform
+    - apps
+
+steps:
+  # TODO DRY with nix develop and custom entrypoint https://github.com/woodpecker-ci/woodpecker/pull/2985,
+  # but first we need a Nix cache. See the nix-cache branch for the WIP.
+  diff:
+    image: nixery.dev/shell/git/python3/kubernetes-helm/diffutils/dyff # TODO replace with nix develop
+    commands:
+      - ./scripts/helm-diff --repository "${CI_REPO_CLONE_URL}" --source "${CI_COMMIT_SOURCE_BRANCH}" --target "${CI_COMMIT_TARGET_BRANCH}" --subpath "${STACK}"
+    when:
+      - event: pull_request
+        path: '${STACK}/**'
+    depends_on: []

flake.nix

@@ -26,6 +26,7 @@
             diffutils
             docker
             docker-compose_1 # TODO upgrade to version 2
+            dyff
             git
             go
             gotestsum

scripts/helm-diff

@@ -0,0 +1,84 @@
+#!/usr/bin/env python
+
+from argparse import ArgumentParser
+from glob import glob
+from os import path
+from subprocess import run
+from tempfile import mkdtemp, NamedTemporaryFile
+
+
+def clone_repository(repo, branch, target_path):
+    run(
+        ['git', 'clone', repo, '--depth', '1', '--branch', branch, target_path],
+        check=True
+    )
+
+
+def render_helm_chart(chart_path, namespace, release_name, rendered_path):
+    # Even if there is no Helm chart at the specified chart path, do not raise an error.
+    # This accommodates cases where the entire chart is removed, or a new chart is added.
+    # In such cases, the rendered file will simply be empty.
+    if path.isdir(chart_path):
+        run(
+            ['helm', 'dependency', 'update', chart_path],
+            check=True
+        )
+
+    run(
+        ['helm', 'template', '--namespace', namespace, release_name, chart_path],
+        stdout=open(rendered_path, 'w'),
+        check=True
+    )
+
+
+def changed_charts(source_path, target_path, subpath):
+    changed_charts = []
+
+    # Convert to set for deduplication
+    all_charts = set(
+        glob(f"*", root_dir=f"{source_path}/{subpath}")
+        + glob(f"*", root_dir=f"{target_path}/{subpath}")
+    )
+
+    for chart in all_charts:
+        source_chart_path = path.join(source_path, subpath, chart)
+        target_chart_path = path.join(target_path, subpath, chart)
+
+        if run(['diff', source_chart_path, target_chart_path], capture_output=True).returncode != 0:
+            changed_charts.append(chart)
+
+    return changed_charts
+
+
+def main():
+    parser = ArgumentParser(description='Compare Helm charts in a directory between two Git revisions.')
+    parser.add_argument('--repository', required=True, help='Repository to clone')
+    parser.add_argument('--source', required=True, help='Source branch (e.g. pull request branch)')
+    parser.add_argument('--target', required=True, help='Target branch (e.g. master branch)')
+    parser.add_argument('--subpath', required=True, help='Subpath containing the charts (e.g. system)')
+
+    args = parser.parse_args()
+
+    source_path = mkdtemp()
+    target_path = mkdtemp()
+
+    clone_repository(args.repository, args.source, source_path)
+    clone_repository(args.repository, args.target, target_path)
+
+    for chart in changed_charts(source_path, target_path, args.subpath):
+        with NamedTemporaryFile(suffix='.yaml', mode='w+', delete=False) as f_source, NamedTemporaryFile(suffix='.yaml', mode='w+', delete=False) as f_target:
+            render_helm_chart(f"{source_path}/{args.subpath}/{chart}", chart, chart, f_source.name)
+            render_helm_chart(f"{target_path}/{args.subpath}/{chart}", chart, chart, f_target.name)
+
+            diff_result = run(
+                ['dyff', 'between', '--omit-header', '--use-go-patch-style', '--color=on', '--truecolor=off', f_target.name, f_source.name],
+                capture_output=True,
+                text=True,
+                check=True
+            )
+
+            print(diff_result.stdout)
+
+
+if __name__ == "__main__":
+    main()