changelog: tailor failure-comment wording to missing label kind (#146)

The post-failure-comment script always announced "no matching type
label found on this PR". Now that `changelog evaluate-pr` can route a
missing product label through the same comment-failure path, the
headline becomes misleading when only the product label is missing.

Pick the headline based on which label tables are populated:
type-only, product-only, or both. The per-section formatting and the
skip-labels section are unchanged.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: cotti

changelog/submit/apply/scripts/post-failure-comment.js

@@ -3,30 +3,32 @@ const { TITLE, upsertComment } = require('./comment-helper');
 module.exports = async ({ github, context, core }) => {
   const prNumber = parseInt(process.env.PR_NUMBER, 10);
   const configFile = process.env.CONFIG_FILE || 'docs/changelog.yml';
-  const labelRows = process.env.LABEL_TABLE || '';
-  const productLabelRows = process.env.PRODUCT_LABEL_TABLE || '';
+  const labelRows = (process.env.LABEL_TABLE || '').trim();
+  const productLabelRows = (process.env.PRODUCT_LABEL_TABLE || '').trim();
   const skipLabels = process.env.SKIP_LABELS || '';
 
-  let labelSection;
-  if (labelRows.trim()) {
-    labelSection = [
-      '',
-      '🔖 Add one of these **type** labels to your PR:',
-      '',
-      labelRows,
-    ].join('\n');
+  const hasTypeIssue = !!labelRows;
+  const hasProductIssue = !!productLabelRows;
+
+  let headline;
+  if (hasTypeIssue && hasProductIssue) {
+    headline = '⚠️ **Cannot generate changelog:** required type and product labels are missing on this PR.';
+  } else if (hasProductIssue) {
+    headline = '⚠️ **Cannot generate changelog:** no matching product label found on this PR.';
   } else {
-    labelSection = `\nAdd a type label that matches your \`pivot.types\` configuration in \`${configFile}\`.`;
+    headline = '⚠️ **Cannot generate changelog:** no matching type label found on this PR.';
+  }
+
+  const sections = [];
+
+  if (hasTypeIssue) {
+    sections.push(['', '🔖 Add one of these **type** labels to your PR:', '', labelRows].join('\n'));
+  } else if (!hasProductIssue) {
+    sections.push(`\nAdd a type label that matches your \`pivot.types\` configuration in \`${configFile}\`.`);
   }
 
-  let productSection = '';
-  if (productLabelRows.trim()) {
-    productSection = [
-      '',
-      '📦 Add one or more **product** labels:',
-      '',
-      productLabelRows,
-    ].join('\n');
+  if (hasProductIssue) {
+    sections.push(['', '📦 Add one or more **product** labels to your PR:', '', productLabelRows].join('\n'));
   }
 
   let skipSection;
@@ -40,9 +42,8 @@ module.exports = async ({ github, context, core }) => {
   const body = [
     TITLE,
     '',
-    '⚠️ **Cannot generate changelog:** no matching type label found on this PR.',
-    labelSection,
-    productSection,
+    headline,
+    ...sections,
     skipSection,
     '',
     `📄 See \`${configFile}\` for the full changelog configuration.`,