feat: Add subjectPatternError option to set custom sub validation error

README.md

@@ -51,6 +51,12 @@ jobs:
           # Configure additional validation for the subject based on a regex.
           # This example ensures the subject doesn't start with an uppercase character.
           subjectPattern: ^(?![A-Z]).+$
+          # If `subjectPattern` is configured, you can use this property to override
+          # the default error message that is shown when the pattern doesn't match.
+          # The variables `subject` and `title` can be used within the message.
+          subjectPatternError: |
+            The subject "{subject}" found in the pull request title "{title}" didn't match the configured pattern.
+            Please ensure that the subject doesn't start with an uppercase character.
           # For work-in-progress PRs you can typically use draft pull requests 
           # from Github. However, private repositories on the free plan don't have 
           # this option and therefore this action allows you to opt-in to using the 

action.yml

@@ -20,6 +20,9 @@ inputs:
   subjectPattern:
     description: "Configure additional validation for the subject based on a regex. E.g. '^(?![A-Z]).+$' ensures the subject doesn't start with an uppercase character."
     required: false
+  subjectPatternError:
+    description: "If `subjectPattern` is configured, you can use this property to override the default error message that is shown when the pattern doesn't match. The variables `subject` and `title` can be used within the message."
+    required: false
   wip:
     description: "For work-in-progress PRs you can typically use draft pull requests from Github. However, private repositories on the free plan don't have this option and therefore this action allows you to opt-in to using the special '[WIP]' prefix to indicate this state. This will avoid the validation of the PR title and the pull request checks remain pending. Note that a second check will be reported if this is enabled."
     required: false

src/formatMessage.js

@@ -0,0 +1,9 @@
+module.exports = function formatMessage(message, values) {
+  let formatted = message;
+  if (values) {
+    Object.entries(values).forEach(([key, value]) => {
+      formatted = formatted.replace(new RegExp(`{${key}}`, 'g'), value);
+    });
+  }
+  return formatted;
+};

src/formatMessage.test.js

@@ -0,0 +1,30 @@
+const formatMessage = require('./formatMessage');
+
+it('handles a string without variables', () => {
+  const message = 'this is test';
+  expect(formatMessage(message)).toEqual(message);
+});
+
+it('replaces a variable', () => {
+  expect(
+    formatMessage('this is {subject} test', {subject: 'my subject'})
+  ).toEqual('this is my subject test');
+});
+
+it('replaces multiple variables', () => {
+  expect(
+    formatMessage('this {title} is {subject} test', {
+      subject: 'my subject',
+      title: 'my title'
+    })
+  ).toEqual('this my title is my subject test');
+});
+
+it('replaces multiple instances of a variable', () => {
+  expect(
+    formatMessage(
+      '99 bottles of {beverage} on the wall, 99 bottles of {beverage}.',
+      {beverage: 'beer'}
+    )
+  ).toEqual('99 bottles of beer on the wall, 99 bottles of beer.');
+});

src/index.js

@@ -6,7 +6,14 @@ const validatePrTitle = require('./validatePrTitle');
 module.exports = async function run() {
   try {
     const client = github.getOctokit(process.env.GITHUB_TOKEN);
-    const {types, scopes, requireScope, wip, subjectPattern} = parseConfig();
+    const {
+      types,
+      scopes,
+      requireScope,
+      wip,
+      subjectPattern,
+      subjectPatternError
+    } = parseConfig();
 
     const contextPullRequest = github.context.payload.pull_request;
     if (!contextPullRequest) {
@@ -38,7 +45,8 @@ module.exports = async function run() {
           types,
           scopes,
           requireScope,
-          subjectPattern
+          subjectPattern,
+          subjectPatternError
         });
       } catch (error) {
         validationError = error;

src/parseConfig.js

@@ -21,10 +21,24 @@ module.exports = function parseConfig() {
     subjectPattern = ConfigParser.parseString(process.env.INPUT_SUBJECTPATTERN);
   }
 
+  let subjectPatternError;
+  if (process.env.INPUT_SUBJECTPATTERNERROR) {
+    subjectPatternError = ConfigParser.parseString(
+      process.env.INPUT_SUBJECTPATTERNERROR
+    );
+  }
+
   let wip;
   if (process.env.INPUT_WIP) {
     wip = ConfigParser.parseBoolean(process.env.INPUT_WIP);
   }
 
-  return {types, scopes, requireScope, wip, subjectPattern};
+  return {
+    types,
+    scopes,
+    requireScope,
+    wip,
+    subjectPattern,
+    subjectPatternError
+  };
 };

src/validatePrTitle.js

@@ -1,12 +1,13 @@
 const conventionalCommitsConfig = require('conventional-changelog-conventionalcommits');
 const conventionalCommitTypes = require('conventional-commit-types');
 const parser = require('conventional-commits-parser').sync;
+const formatMessage = require('./formatMessage');
 
 const defaultTypes = Object.keys(conventionalCommitTypes.types);
 
 module.exports = async function validatePrTitle(
   prTitle,
-  {types, scopes, requireScope, subjectPattern} = {}
+  {types, scopes, requireScope, subjectPattern, subjectPatternError} = {}
 ) {
   if (!types) types = defaultTypes;
 
@@ -66,6 +67,15 @@ module.exports = async function validatePrTitle(
   if (subjectPattern) {
     const match = result.subject.match(new RegExp(subjectPattern));
 
+    if (subjectPatternError) {
+      throw new Error(
+        formatMessage(subjectPatternError, {
+          subject: result.subject,
+          title: prTitle
+        })
+      );
+    }
+
     if (!match) {
       throw new Error(
         `The subject "${result.subject}" found in pull request title "${prTitle}" doesn't match the configured pattern "${subjectPattern}".`

src/validatePrTitle.test.js

@@ -108,6 +108,29 @@ describe('description validation', () => {
     await validatePrTitle('fix: sK!"§4123');
   });
 
+  it('uses the `subjectPatternError` if available when the `subjectPattern` does not match', async () => {
+    const customError =
+      'The subject found in the pull request title cannot start with an uppercase character.';
+    await expect(
+      validatePrTitle('fix: Foobar', {
+        subjectPattern: '^(?![A-Z]).+$',
+        subjectPatternError: customError
+      })
+    ).rejects.toThrow(customError);
+  });
+
+  it('interpolates variables into `subjectPatternError`', async () => {
+    await expect(
+      validatePrTitle('fix: Foobar', {
+        subjectPattern: '^(?![A-Z]).+$',
+        subjectPatternError:
+          'The subject "{subject}" found in the pull request title "{title}" cannot start with an uppercase character.'
+      })
+    ).rejects.toThrow(
+      'The subject "Foobar" found in the pull request title "fix: Foobar" cannot start with an uppercase character.'
+    );
+  });
+
   it('throws for invalid subjects', async () => {
     await expect(
       validatePrTitle('fix: Foobar', {