chore(ci): auto-label PR on semantic title (#403)

Author: heitorlessa

.github/workflows/label_pr_on_title.yml

@@ -0,0 +1,91 @@
+name: Label PR based on title
+
+# pull_request_target event sends an admin GH token to forks
+# this however depends on another workflow so it all runs within the base repo safely
+# "Record PR number" workflow safely captures PR title and number
+# This workflow uses this information to label the PR based on its semantic title
+on:
+  workflow_run:
+    workflows: ["Record PR number"]
+    types:
+      - completed
+
+jobs:
+  label_pr:
+    runs-on: ubuntu-latest
+    # Guardrails to only ever run if PR recording workflow was indeed
+    # run in a PR event and ran successfully
+    if: >
+      ${{ github.event.workflow_run.event == 'pull_request' &&
+      github.event.workflow_run.conclusion == 'success' }}
+    steps:
+      - name: 'Download artifact'
+        uses: actions/github-script@v5
+        # For security, we only download artifacts tied to the successful PR recording workflow
+        with:
+          script: |
+            const fs = require('fs');
+
+            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               run_id: ${{github.event.workflow_run.id }},
+            });
+
+            const matchArtifact = artifacts.data.artifacts.filter(artifact => artifact.name == "pr")[0];
+
+            const artifact = await github.rest.actions.downloadArtifact({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               artifact_id: matchArtifact.id,
+               archive_format: 'zip',
+            });
+
+            fs.writeFileSync('${{github.workspace}}/pr.zip', Buffer.from(artifact.data));
+      # NodeJS standard library doesn't provide ZIP capabilities; use system `unzip` command instead
+      - run: unzip pr.zip
+
+      - name: 'Label PR based on title'
+        uses: actions/github-script@v5
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          # This safely runs in our base repo, not on fork
+          # thus allowing us to provide a write access token to label based on PR title
+          # and label PR based on semantic title accordingly
+          script: |
+            const fs = require('fs');
+            const pr_number = Number(fs.readFileSync('./number'));
+            const pr_title = fs.readFileSync('./title', 'utf-8').trim();
+
+            const FEAT_REGEX = /feat(\((\w+)\))?(\:.+)/
+            const BUG_REGEX = /(fix|bug)(\((\w+)\))?(\:.+)/
+            const DOCS_REGEX = /(docs|doc)(\((\w+)\))?(\:.+)/
+            const CHORE_REGEX = /(chore)(\((\w+)\))?(\:.+)/
+            const DEPRECATED_REGEX = /(deprecated)(\((\w+)\))?(\:.+)/
+            const REFACTOR_REGEX = /(refactor)(\((\w+)\))?(\:.+)/
+
+            const labels = {
+                "feature": FEAT_REGEX,
+                "bug": BUG_REGEX,
+                "documentation": DOCS_REGEX,
+                "internal": CHORE_REGEX,
+                "enhancement": REFACTOR_REGEX,
+                "deprecated": DEPRECATED_REGEX,
+            }
+
+            for (const label in labels) {
+                const matcher = new RegExp(labels[label])
+                const isMatch = matcher.exec(pr_title)
+                if (isMatch != null) {
+                    console.info(`Auto-labeling PR ${pr_number} with ${label}`)
+
+                    await github.rest.issues.addLabels({
+                      issue_number: pr_number,
+                      owner: context.repo.owner,
+                      repo: context.repo.repo,
+                      labels: [label]
+                    })
+
+                    break
+                }
+            }

.github/workflows/record_pr.yml

@@ -0,0 +1,21 @@
+name: Record PR number
+
+on:
+  pull_request:
+    types: [opened, edited]
+
+jobs:
+  record:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Save PR number
+        run: |
+          mkdir -p ./pr
+          echo ${{ github.event.number }} > ./pr/number
+          echo "${{ github.event.pull_request.title }}" > ./pr/title
+      - uses: actions/upload-artifact@v2
+        with:
+          name: pr
+          path: pr/