Create action for assigning, labeling new PRs

.github/workflows/new_pr_labeler.yml

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+name: new_pr_labeler
+on:
+  pull_request_target:
+    types:
+      - opened
+jobs:
+  label_pr:
+    # Continue only if the PR was opened in the same repository that is running this action:
+    if: ${{ github.repository == github.event.repository.full_name }}
+    permissions:
+      contents: read
+      issues: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+      - run: npm install @octokit/action
+      - run: node scripts/gh_scripts/new_pr_labeler.mjs ${{ github.repository }} ${{ github.event.pull_request.user.login }} ${{ github.event.pull_request.number }} "$PR_BODY"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_BODY: ${{ github.event.pull_request.body }}

scripts/gh_scripts/new_pr_labeler.mjs

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+/**
+ * Script to automatically assign and label new GitHub pull requests.
+ *
+ * Usage:
+ * `node new_pr_labeler REPO_NAME PR_AUTHOR PR_NUMBER PR_BODY...`
+ *
+ * Where:
+ * `REPO_NAME` is the owner and repository (e.g. "internetarchive/openlibrary")
+ * `PR_AUTHOR` is the username of the PR's author
+ * `PR_NUMBER` is the newly created PR's number
+ * `PR_BODY`   is the body of the pull request
+ *
+ * Broadly, this script does the following:
+ * 1. Searches the given PR body for a "closes" statement
+ * 2. Fetches the issue referenced by the "closes" statement, storing references
+ *    to the first priority and lead label encountered
+ * 3. Updates PR, adding same priority label as issue, and assigning the lead (if
+ *    they are not also the author)
+ */
+import { Octokit } from "@octokit/action";
+
+console.log('Script starting....')
+const octokit = new Octokit()
+await main()
+console.log('Script terminated....')
+
+async function main() {
+    // Parse and assign all command-line variables
+    const {fullRepoName, prAuthor, prNumber, prBody} = parseArgs()
+
+    // Look for "Closes:" statement, storing the issue number (if present)
+    const issueNumber = findLinkedIssue(prBody)
+
+    if (!issueNumber) {
+        console.log('No linked issue found for this pull request.')
+        return
+    }
+
+    // Fetch the issue
+    const [repoOwner, repoName] = fullRepoName.split('/')
+    const linkedIssue = await octokit.request('GET /repos/{owner}/{repo}/issues/{issue_number}', {
+        owner: repoOwner,
+        repo: repoName,
+        issue_number: issueNumber,
+        headers: {
+          'X-GitHub-Api-Version': '2022-11-28'
+        }
+      })
+    if (!linkedIssue) {
+        console.log(`An issue occurred while fetching issue #${issueNumber}`)
+        process.exit(1)
+    }
+
+    // Check the issue's labels for the priority and lead
+    let leadName
+    let priority
+    for (const label of linkedIssue.data.labels) {
+        if (!leadName && label.name.startsWith('Lead: @')) {
+            leadName = label.name.split('@')[1]
+        }
+        if (!priority && label.name.match(/Priority: [012]/)) {
+            priority = label.name
+        }
+    }
+
+    // Don't assign lead to PR if PR author is the issue lead
+    const assignLead = leadName && !(leadName === prAuthor)
+
+    // Update PR, adding assignee and priority label
+    if (assignLead) {
+        await octokit.request('POST /repos/{owner}/{repo}/issues/{issue_number}/assignees', {
+            owner: repoOwner,
+            repo: repoName,
+            issue_number: prNumber,
+            assignees: [leadName],
+            headers: {
+              'X-GitHub-Api-Version': '2022-11-28'
+            }
+          })
+    }
+
+    if (priority) {
+        await octokit.request('POST /repos/{owner}/{repo}/issues/{issue_number}/labels', {
+            owner: repoOwner,
+            repo: repoName,
+            issue_number: prNumber,
+            labels: [priority],
+            headers: {
+              'X-GitHub-Api-Version': '2022-11-28'
+            }
+          })
+    }
+}
+
+/**
+ * Returns an object containing the parsed command-line arguments.
+ *
+ * Any newline characters in the PR's body are replaced by space characters.
+ *
+ * @returns {Record<string, string>}
+ */
+function parseArgs() {
+    if (process.argv.length < 6) {
+        console.log('Unexpected number of arguments.')
+        process.exit(1)
+    }
+    const prBody = process.argv.slice(5).join(' ')
+    return {
+        fullRepoName: process.argv[2],
+        prAuthor: process.argv[3],
+        prNumber: process.argv[4],
+        prBody: prBody
+    }
+}
+
+/**
+ * Finds first "Closes" statement in the given pull request body, then
+ * returns the number of the linked issue or an empty string, if none exists.
+ *
+ * @param {string} body The body of a GitHub pull request
+ * @returns {string} The number of the linked issue that will be closed
+ *                   by this pull request, or an empty string if no
+ *                   "Closes" statement is found.
+ */
+function findLinkedIssue(body) {
+    let lowerBody = body.toLowerCase()
+    const matches = lowerBody.match(/closes #(\d+)/)
+    return matches.length ? Number(matches[1]) : ''
+}