Add Cloudflare PR preview deployments

.github/workflows/ci.yml

@@ -6,6 +6,12 @@ on:
 
 permissions:
   contents: read
+  deployments: write
+  pull-requests: write
+
+concurrency:
+  group: ci-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test-and-build:
@@ -29,3 +35,50 @@ jobs:
         run: |
           npm ci
           npm run build
+      - name: Deploy PR preview
+        if: >-
+          github.event_name == 'pull_request' &&
+          github.event.pull_request.head.repo.full_name == github.repository
+        id: preview
+        uses: cloudflare/wrangler-action@v4
+        with:
+          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          accountId: ${{ vars.CLOUDFLARE_ACCOUNT_ID }}
+          command: >-
+            pages deploy dist
+            --project-name=display-list-explorer
+            --branch=pr-${{ github.event.number }}
+          gitHubToken: ${{ secrets.GITHUB_TOKEN }}
+      - name: Comment preview URLs
+        if: >-
+          github.event_name == 'pull_request' &&
+          github.event.pull_request.head.repo.full_name == github.repository &&
+          steps.preview.outcome == 'success'
+        uses: actions/github-script@v9
+        env:
+          COMMIT_SHA: ${{ github.event.pull_request.head.sha }}
+          SNAPSHOT_URL: ${{ steps.preview.outputs.deployment-url }}
+          STABLE_URL: ${{ steps.preview.outputs.pages-deployment-alias-url }}
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const sha = process.env.COMMIT_SHA;
+            const snapshotUrl = process.env.SNAPSHOT_URL;
+            const stableUrl = process.env.STABLE_URL;
+            const shortSha = sha.slice(0, 7);
+            const commitUrl = `${process.env.GITHUB_SERVER_URL}/${context.repo.owner}/${context.repo.repo}/commit/${sha}`;
+            const body = [
+              "## Cloudflare Pages preview",
+              "",
+              `- **Latest PR preview:** [${stableUrl}](${stableUrl})`,
+              `- **Snapshot for [\`${shortSha}\`](${commitUrl}):** [${snapshotUrl}](${snapshotUrl})`,
+              "",
+              "The PR URL always points to the latest deployment; the commit snapshot is immutable.",
+            ].join("\n");
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body,
+            });

README.md

@@ -64,6 +64,12 @@ swift test
 
 The Pages workflow deploys every push to `main` and can also be run manually from any branch through `workflow_dispatch`. It tests the converter, builds the SwiftWasm package, bundles the site with the repository's Pages base path, and deploys the `dist` artifact to <https://openswiftuiproject.github.io/DisplayListExplorer/>.
 
+## Pull request previews
+
+Pull requests opened from branches in this repository are deployed to an isolated Cloudflare Pages preview after CI succeeds. Each pull request receives a stable branch alias such as `https://pr-42.display-list-explorer.pages.dev`, while every update also creates an immutable deployment URL. GitHub attaches the resulting URL to the pull request as a deployment and posts both URLs in a commit-specific PR comment, preserving access to earlier snapshots as new commits are pushed.
+
+The workflow expects a `CLOUDFLARE_API_TOKEN` repository secret with Cloudflare Pages edit access and a `CLOUDFLARE_ACCOUNT_ID` repository variable. Pull requests from forks still run the converter and site build, but skip deployment because repository secrets are not exposed to fork workflows.
+
 ## License
 
 DisplayList Explorer is available under the MIT License. Third-party attributions are listed in [`THIRD_PARTY_NOTICES.md`](THIRD_PARTY_NOTICES.md).