feat: outputs the error messages

.github/workflows/lint-pr-title-preview-outputErrorMessage

@@ -0,0 +1,28 @@
+name: "Lint PR title preview (current branch, outputErrorMessage)"
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - synchronize
+
+jobs:
+  main:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
+      - run: yarn install
+      - run: yarn build
+      - uses: ./
+        id: lint_pr_title
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Comment on PR 
+        if: always()
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          message: ${{ steps.lint_pr_title.outputs.ERROR_MESSAGE }}

src/validatePrTitle.js

@@ -1,3 +1,4 @@
+const core = require('@actions/core');
 const conventionalCommitsConfig = require('conventional-changelog-conventionalcommits');
 const conventionalCommitTypes = require('conventional-commit-types');
 const parser = require('conventional-commits-parser').sync;
@@ -52,30 +53,29 @@ module.exports = async function validatePrTitle(
   }
 
   if (!result.type) {
-    throw new Error(
+    raiseError(
       `No release type found in pull request title "${prTitle}". Add a prefix to indicate what kind of release this pull request corresponds to. For reference, see https://www.conventionalcommits.org/\n\n${printAvailableTypes()}`
     );
   }
 
   if (!result.subject) {
-    throw new Error(`No subject found in pull request title "${prTitle}".`);
+    raiseError(`No subject found in pull request title "${prTitle}".`);
   }
 
   if (!types.includes(result.type)) {
-    throw new Error(
+    raiseError(
       `Unknown release type "${
         result.type
       }" found in pull request title "${prTitle}". \n\n${printAvailableTypes()}`
     );
   }
 
   if (requireScope && !result.scope) {
-    let msg = `No scope found in pull request title "${prTitle}".`;
+    let message = `No scope found in pull request title "${prTitle}".`;
     if (scopes) {
-      msg += ` Use one of the available scopes: ${scopes.join(', ')}.`;
+      message += ` Use one of the available scopes: ${scopes.join(', ')}.`;
     }
-
-    throw new Error(msg);
+    raiseError(message);
   }
 
   const givenScopes = result.scope
@@ -84,7 +84,7 @@ module.exports = async function validatePrTitle(
 
   const unknownScopes = givenScopes ? givenScopes.filter(isUnknownScope) : [];
   if (scopes && unknownScopes.length > 0) {
-    throw new Error(
+    raiseError(
       `Unknown ${
         unknownScopes.length > 1 ? 'scopes' : 'scope'
       } "${unknownScopes.join(
@@ -99,7 +99,7 @@ module.exports = async function validatePrTitle(
     ? givenScopes.filter(isDisallowedScope)
     : [];
   if (disallowScopes && disallowedScopes.length > 0) {
-    throw new Error(
+    raiseError(
       `Disallowed ${
         disallowedScopes.length === 1 ? 'scope was' : 'scopes were'
       } found: ${disallowScopes.join(', ')}`
@@ -113,8 +113,7 @@ module.exports = async function validatePrTitle(
         title: prTitle
       });
     }
-
-    throw new Error(message);
+    raiseError(message);
   }
 
   if (subjectPattern) {
@@ -133,4 +132,10 @@ module.exports = async function validatePrTitle(
       );
     }
   }
+
+  function raiseError(message) {
+    core.setOutput('ERROR_MESSAGE', message);
+
+    throw new Error(message);
+  }
 };