Add a pull request standards workflow

.github/workflows/blocking-labels.yaml

@@ -30,6 +30,7 @@ jobs:
               "Do Not Review",
               "Blocked",
               "has-parent",
+              "Needs Template",
             ];
             const prLabels = context.payload.pull_request.labels.map(
               (l) => l.name

.github/workflows/pull-request-standards.yaml

@@ -0,0 +1,185 @@
+name: Pull request standards
+
+on:
+  pull_request_target: # zizmor: ignore[dangerous-triggers] -- safe: reads PR metadata from event payload only, no PR code checkout
+    types:
+      - opened
+      - edited
+      - reopened
+      - ready_for_review
+    branches:
+      - dev
+
+permissions: {}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    name: Check pull request follows contribution standards
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write # To label and comment on pull requests
+    steps:
+      - name: Check pull request standards
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const pr = context.payload.pull_request;
+
+            // Exempt bots (Copilot agent, dependabot), drafts, and maintainers.
+            if (pr.user.type === "Bot") {
+              core.info(`Skipping bot author: ${pr.user.login}`);
+              return;
+            }
+            if (pr.draft) {
+              core.info("Skipping draft pull request");
+              return;
+            }
+            try {
+              await github.rest.orgs.checkMembershipForUser({
+                org: "home-assistant",
+                username: pr.user.login,
+              });
+              core.info(`Skipping organization member: ${pr.user.login}`);
+              return;
+            } catch (error) {
+              core.info(`${pr.user.login} is not an organization member, checking standards`);
+            }
+
+            const label = "Needs Template";
+            const marker = "<!-- pr-standards-check -->";
+            const { owner, repo } = context.repo;
+            const issue_number = pr.number;
+
+            const body = (pr.body || "").replace(/<!--[\s\S]*?-->/g, "");
+            const normalized = body.toLowerCase();
+
+            // Ignore 404s from mutations that race manual edits or cancelled runs.
+            const ignoreMissing = async (fn) => {
+              try {
+                await fn();
+              } catch (error) {
+                if (error.status === 404) {
+                  core.info("Target already removed, nothing to do");
+                  return;
+                }
+                throw error;
+              }
+            };
+
+            // Hide/restore our comment via GraphQL (REST cannot minimize).
+            const setMinimized = async (subjectId, minimized) => {
+              const mutation = minimized
+                ? `mutation($id: ID!) {
+                     minimizeComment(input: { subjectId: $id, classifier: RESOLVED }) {
+                       clientMutationId
+                     }
+                   }`
+                : `mutation($id: ID!) {
+                     unminimizeComment(input: { subjectId: $id }) {
+                       clientMutationId
+                     }
+                   }`;
+              try {
+                await github.graphql(mutation, { id: subjectId });
+              } catch (error) {
+                core.info(
+                  `Could not ${minimized ? "minimize" : "restore"} comment: ${error.message}`
+                );
+              }
+            };
+
+            // Content of a "## <name>" section, or null when the heading is absent.
+            const section = (name) => {
+              const match = body.match(
+                new RegExp(`##\\s*${name}([\\s\\S]*?)(?=\\n##\\s|$)`, "i")
+              );
+              return match ? match[1] : null;
+            };
+
+            const problems = [];
+
+            const requiredHeadings = [
+              "## proposed change",
+              "## type of change",
+              "## checklist",
+            ];
+            if (requiredHeadings.some((h) => !normalized.includes(h))) {
+              problems.push(
+                "Use the pull request template without removing its sections."
+              );
+            }
+
+            const typeOfChange = section("type of change");
+            if (typeOfChange !== null) {
+              const ticked = (typeOfChange.match(/-\s*\[[xX]\]/g) || []).length;
+              if (ticked !== 1) {
+                problems.push(
+                  'Select exactly one option under "Type of change".'
+                );
+              }
+            }
+
+            const proposedChange = section("proposed change");
+            if (proposedChange !== null && proposedChange.trim().length === 0) {
+              problems.push('Describe your changes under "Proposed change".');
+            }
+
+            const isValid = problems.length === 0;
+
+            const comments = await github.paginate(
+              github.rest.issues.listComments,
+              { owner, repo, issue_number, per_page: 100 }
+            );
+            const existing = comments.find((c) => c.body.includes(marker));
+            const hasLabel = pr.labels.some((l) => l.name === label);
+
+            if (isValid) {
+              core.info("Pull request standards met");
+
+              if (hasLabel) {
+                await ignoreMissing(() =>
+                  github.rest.issues.removeLabel({
+                    owner, repo, issue_number, name: label,
+                  })
+                );
+              }
+              if (existing) {
+                await setMinimized(existing.node_id, true);
+              }
+              return;
+            }
+
+            core.info(`Pull request standards not met:\n- ${problems.join("\n- ")}`);
+
+            if (!hasLabel) {
+              await github.rest.issues.addLabels({
+                owner, repo, issue_number, labels: [label],
+              });
+            }
+
+            const message =
+              `${marker}\n` +
+              `Hey @${pr.user.login}!\n\n` +
+              `Thank you for your contribution! To help reviewers, please update ` +
+              `this pull request to follow our pull request standards:\n\n` +
+              problems.map((p) => `- ${p}`).join("\n") +
+              `\n\n` +
+              `Please complete the ` +
+              `[PR template](https://github.com/home-assistant/frontend/blob/dev/.github/PULL_REQUEST_TEMPLATE.md?plain=1) ` +
+              `and see the [developer docs](https://developers.home-assistant.io/docs/review-process) ` +
+              `for more on creating a great pull request (see point 6).`;
+
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner, repo, comment_id: existing.id, body: message,
+              });
+              await setMinimized(existing.node_id, false);
+            } else {
+              await github.rest.issues.createComment({
+                owner, repo, issue_number, body: message,
+              });
+            }