[ci skip] Rework workflows to support optional paperclip build (#8583)

.github/workflows/build.yml

@@ -1,33 +1,87 @@
 # Here lie dragons!
 #
-# Note that there is no artifact step in this script. We do not want Paperclip
-# jars to be built for every push & PR; our CI handles pushes to branches, while
-# PRs can themselves link to Paperclip jars if it is necessary. Official such
-# PRs will take use of testing builds.
+# This action either builds the server or
+# builds a paperclip jar to be updated in the body
+# of the PR relating to this action.
 
 name: Build Paper
-on: [push, pull_request]
+on:
+  push:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - labeled
 
 jobs:
-    build:
-        # Only run on PRs if the source branch is on someone else's repo
-        if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}
-        runs-on: ubuntu-latest
-        strategy:
-            matrix:
-                java: [17]
-            fail-fast: true
-        steps:
-            - uses: actions/checkout@v3
-            - name: JDK ${{ matrix.java }}
-              uses: actions/setup-java@v3.6.0
-              with:
-                  java-version: ${{ matrix.java }}
-                  cache: 'gradle'
-                  distribution: 'temurin'
-            - name: Patch and build
-              run: |
-                  git config --global user.email "no-reply@github.com"
-                  git config --global user.name "Github Actions"
-                  ./gradlew applyPatches --stacktrace
-                  ./gradlew build --stacktrace
+  build:
+    # Only run on PRs if the source branch is on someone else's repo and the pr is not labeled with `build-pr-jar`
+    if: github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [17]
+      fail-fast: true
+    steps:
+      - uses: actions/checkout@v3
+      - name: JDK ${{ matrix.java }}
+        uses: actions/setup-java@v3.6.0
+        with:
+          java-version: ${{ matrix.java }}
+          distribution: 'temurin'
+      - name: Setup Gradle
+        uses: gradle/gradle-build-action@v2
+
+      - name: Configure Build
+        uses: actions/github-script@v6
+        id: determine
+        with:
+          script: |
+            const {owner, repo} = context.repo;
+            const event_name = "${{ github.event_name }}";
+            const event = ${{ toJSON(github.event) }};
+            const ref_type = "${{ github.ref_type }}";
+            const ref_name = "${{ github.ref_name }}";
+            const result = {
+              action: "build"
+            };
+
+            if (event_name === "push" && ref_type === "branch") {
+              const {data: pulls} = await github.rest.pulls.list({ owner, repo, head: `${owner}:${ref_name}`, state: "open" });
+              const pull = pulls.find((pr) => !!pr.labels.find((l) => l.name === "build-pr-jar"));
+              if (pull) {
+                result["pr"] = pull.number;
+                result["action"] = "paperclip";
+                core.info(`This is a push action but to a branch with an open PR with the build paperclip label (${JSON.stringify(result)})`);
+                return result;
+              }
+            } else if (event_name === "pull_request" && event.pull_request.labels.find((l) => l.name === "build-pr-jar")) {
+              result["pr"] = event.pull_request.number;
+              result["action"] = "paperclip";
+              core.info(`This is a pull request action with a build paperclip label (${JSON.stringify(result)})`);
+              return result;
+            }
+            core.info("This will not build a paperclip jar");
+            return result;
+
+      - name: Apply Patches
+        run: |
+          git config --global user.email "no-reply@github.com"
+          git config --global user.name "Github Actions"
+          ./gradlew applyPatches --stacktrace
+
+      - name: Build
+        if: fromJSON(steps.determine.outputs.result).action == 'build'
+        run: ./gradlew build --stacktrace
+
+      - name: Create Paperclip Jar
+        if: fromJSON(steps.determine.outputs.result).action == 'paperclip'
+        run: ./gradlew createReobfPaperclipJar --stacktrace
+
+      - name: Upload Paperclip Jar
+        if: fromJSON(steps.determine.outputs.result).action == 'paperclip'
+        uses: actions/upload-artifact@v3
+        with:
+          name: paper-${{ fromJSON(steps.determine.outputs.result).pr }}
+          path: build/libs/paper-paperclip-*-reobf.jar

.github/workflows/pr_comment.yml

@@ -0,0 +1,68 @@
+# This workflow run on the completion of the
+# build workflow but only does anything if the
+# triggering workflow uploaded an artifact.
+#
+# Do note that it is then the trigger workflow that
+# determines if this will update the PR text body. All
+# this workflow does is check if an uploaded artifact
+# exists and there is a PR tied to the previous workflow.
+
+name: Comment on pull request
+on:
+  workflow_run:
+    workflows: ['Build Paper']
+    types: [completed]
+jobs:
+  pr_comment:
+    if: github.event.workflow_run.conclusion == 'success'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v6
+        with:
+          # This snippet is public-domain, taken from
+          # https://github.com/oprypin/nightly.link/blob/master/.github/workflows/pr-comment.yml
+          # Modified extensively by Machine_Maker
+          script: |
+            async function updatePR(owner, repo, issue_number, purpose, body) {
+              const { data } = await github.rest.issues.get({owner, repo, issue_number});
+              core.info(JSON.stringify(data, null, 2));
+            
+              const marker = `<!-- bot: ${purpose} -->`;
+            
+              let new_body = data.body ? data.body.trim().split(marker)[0] : "";
+              if (!new_body.trim()) {
+                new_body += `${marker}\n${body}`
+              } else {
+                new_body += `${marker}\n---\n${body}`
+              }
+            
+              core.info(`Updating the text body of PR #${issue_number} in ${owner}/${repo}`);
+              await github.rest.issues.update({owner, repo, issue_number, body: new_body});
+            }
+
+            const {owner, repo} = context.repo;
+            const run_id = ${{github.event.workflow_run.id}};
+            const repo_id = ${{ github.event.repository.id }};
+
+            const pull_requests = ${{ toJSON(github.event.workflow_run.pull_requests) }};
+            if (!pull_requests.length) {
+              return core.notice("This workflow doesn't have any pull requests!");
+            }
+            const pull_request = pull_requests.find((pr) => pr.base.repo.id === repo_id);
+            if (!pull_request) {
+              return core.notice("This workflow doesn't match any pull request!");
+            }
+
+            const artifacts = await github.paginate(github.rest.actions.listWorkflowRunArtifacts, {owner, repo, run_id});
+            if (!artifacts.length) {
+              return core.info("Skipping comment due to no artifact found");
+            }
+            const artifact = artifacts.find((art) => art.name === `paper-${pull_request.number}`);
+            if (!artifact) {
+              return core.info("Skipping comment to no matching artifact found");
+            }
+            
+            const link = `https://nightly.link/${owner}/${repo}/actions/artifacts/${artifact.id}.zip`;
+            const body = `Download the paperclip jar for this pull request: [${artifact.name}.zip](${link})`;
+            core.info(`Adding a link to ${link}`);
+            await updatePR(owner, repo, pull_request.number, "paperclip-pr-build", body);