Incorporate feedback

* Grab most recent PR labels
* Use octokit.rest.issues.addLabels() with a diff of labels
* Squash project labels into bigProjectLabel if too many
* Use template literals
* Handle more edge cases

projects/github-actions/repo-gardening/src/tasks/add-labels/index.js

@@ -1,6 +1,7 @@
 const { getInput } = require( '@actions/core' );
 const debug = require( '../../utils/debug' );
 const getFiles = require( '../../utils/get-files' );
+const getLabels = require( '../../utils/labels/get-labels' );
 
 /* global GitHub, WebhookPayloadPullRequest */
 
@@ -51,17 +52,16 @@ function cleanName( name ) {
 /**
  * Build a list of labels to add to the pull request, based off our file list.
  *
- * @param {GitHub}   octokit   - Initialized Octokit REST client.
- * @param {string}   owner     - Repository owner.
- * @param {string}   repo      - Repository name.
- * @param {string}   number    - PR number.
- * @param {boolean}  isDraft   - Whether the pull request is a draft.
- * @param {boolean}  isRevert  - Whether the pull request is a revert.
- * @param {string[]} curLabels - Current labels on the pull request.
+ * @param {GitHub}  octokit  - Initialized Octokit REST client.
+ * @param {string}  owner    - Repository owner.
+ * @param {string}  repo     - Repository name.
+ * @param {string}  number   - PR number.
+ * @param {boolean} isDraft  - Whether the pull request is a draft.
+ * @param {boolean} isRevert - Whether the pull request is a revert.
  * @return {Promise<Array>} Promise resolving to an array of keywords we'll search for.
  */
-async function getLabelsToAdd( octokit, owner, repo, number, isDraft, isRevert, curLabels ) {
-	const keywords = new Set( curLabels );
+async function getFileDerivedLabels( octokit, owner, repo, number, isDraft, isRevert ) {
+	const keywords = new Set();
 
 	// Get next valid milestone.
 	const files = await getFiles( octokit, owner, repo, number );
@@ -331,47 +331,79 @@ async function addLabels( payload, octokit ) {
 	const { owner, name } = repository;
 	const { draft, title } = pull_request;
 
+	// GitHub allows 100 labels on a PR.
+	// Limit to less than that to allow a buffer for future manual labels.
+	const maxLabels = 90;
+	const bigProjectLabel = '[Project] All the things!';
+
 	// Get labels to add to the PR.
 	const isDraft = !! ( pull_request && draft );
 
 	// If the PR title includes the word "revert", mark it as such.
 	const isRevert = title.toLowerCase().includes( 'revert' );
 
-	const currentLabels = payload.pull_request.labels.map( l => l.name );
-	let labelsToAdd = await getLabelsToAdd(
+	const fileDerivedLabels = await getFileDerivedLabels(
 		octokit,
 		owner.login,
 		name,
 		number,
 		isDraft,
-		isRevert,
-		currentLabels
+		isRevert
 	);
 
+	// Grab current labels on the PR.
+	// We can't rely on payload, as it could be outdated by the time this runs.
+	const currentLabels = await getLabels( octokit, owner.login, name, number );
+
+	// This is an array of labels that GitHub doesn't already have.
+	let labelsToAdd = fileDerivedLabels.filter( label => ! currentLabels.includes( label ) );
+
 	// Nothing new was added, so abort.
-	if ( labelsToAdd.length === currentLabels.length ) {
+	if ( labelsToAdd.length === 0 ) {
 		debug( 'add-labels: No new labels to add to that PR. Aborting.' );
 		return;
 	}
 
-	// GitHub allows 100 labels on a PR. Limit to less than that to allow for additional labels elsewhere.
-	const maxLabels = 90;
-	const bigLabel = 'All the things (>' + maxLabels + ' labels)';
-	if ( labelsToAdd.length > maxLabels ) {
-		debug(
-			'add-labels: GitHub only allows 100 labels on a PR, so limiting to the first ' +
-				maxLabels +
-				'.'
-		);
-		labelsToAdd.splice( maxLabels );
-		labelsToAdd.push( bigLabel );
-	} else if ( labelsToAdd.includes( bigLabel ) ) {
-		labelsToAdd = labelsToAdd.filter( label => label !== bigLabel );
+	// Determine how many labels can safely be added.
+	let maxLabelsToAdd = Math.max( 0, maxLabels - currentLabels.length );
+
+	// Overkill, but let's prevent this label from counting toward the max.
+	const hasBigProjectLabel = currentLabels.includes( bigProjectLabel );
+	if ( hasBigProjectLabel ) {
+		maxLabelsToAdd++;
+	}
+
+	// If there are too many labels, we need to reduce the label count to keep GitHub happy.
+	if ( labelsToAdd.length > maxLabelsToAdd ) {
+		debug( `add-labels: Too many labels! Grouping project labels into '${ bigProjectLabel }'.` );
+
+		// Filter out project-type labels in deference to bigProjectLabel.
+		// In theory we could also remove any existing project-type labels here, but for now
+		// let's not as that would prevent manually adding specific project labels.
+		const projectLabelRegex = /^(\[Action\]|\[Package\]|\[Plugin\]|\[JS Package\])/;
+		labelsToAdd = labelsToAdd.filter( label => ! projectLabelRegex.test( label ) );
+
+		if ( ! hasBigProjectLabel ) {
+			// Add to the beginning of the labels array in case the array gets truncated later on.
+			labelsToAdd.unshift( bigProjectLabel );
+		}
+	} else if ( hasBigProjectLabel ) {
+		await octokit.rest.issues.removeLabel( {
+			owner: owner.login,
+			repo: name,
+			issue_number: number,
+			name: bigProjectLabel,
+		} );
+	}
+	// In the rare chance there would still be too many labels...
+	if ( labelsToAdd.length > maxLabelsToAdd ) {
+		debug( `add-labels: Limiting to the first ${ maxLabels }.` );
+		labelsToAdd.splice( maxLabelsToAdd );
 	}
 
 	debug( `add-labels: Adding labels ${ labelsToAdd } to PR #${ number }` );
 
-	await octokit.rest.issues.setLabels( {
+	await octokit.rest.issues.addLabels( {
 		owner: owner.login,
 		repo: name,
 		issue_number: number,