fix(errors): handle changelog file not found

- Added ChangelogFileNotFoundError
- Improved error handling in changelog service
- Added unit test for file not found error

Author: taj54

src/errors.ts

@@ -43,3 +43,12 @@ export class InvalidManifestError extends CustomError {
     super(message, 'InvalidManifestError');
   }
 }
+
+/**
+ * Error thrown when the changelog file is not found.
+ */
+export class ChangelogFileNotFoundError extends CustomError {
+  constructor(message: string) {
+    super(message, 'ChangelogFileNotFoundError');
+  }
+}

src/services/changelogService.ts

@@ -1,6 +1,7 @@
 import { FileHandler } from '../utils/fileHandler';
 import { GitService } from './gitService';
 import * as core from '@actions/core';
+import { FileNotFoundError } from '../errors';
 
 /**
  * Service for managing the changelog file.
@@ -50,7 +51,18 @@ export class ChangelogService {
    */
   async updateChangelog(changelogContent: string): Promise<void> {
     const changelogPath = this._getChangelogPath();
-    const existingChangelog = await this.fileHandler.readFile(changelogPath);
+    let existingChangelog: string;
+    try {
+      existingChangelog = await this.fileHandler.readFile(changelogPath);
+    } catch (error: any) {
+      if (error.code === 'ENOENT') {
+        throw new FileNotFoundError(
+          `Changelog file not found at ${changelogPath}`,
+        );
+      }
+      throw error;
+    }
+
     const versionMatch = changelogContent.match(/## v(\d+\.\d+\.\d+)/);
     if (versionMatch) {
       const newVersion = versionMatch[0];

tests/services/changelogService.test.ts

@@ -3,6 +3,7 @@ import { ChangelogService } from '../../src/services/changelogService';
 import { FileHandler } from '../../src/utils/fileHandler';
 import { GitService } from '../../src/services/gitService';
 import * as core from '@actions/core';
+import { FileNotFoundError } from '../../src/errors';
 
 vi.mock('@actions/exec');
 vi.mock('../../src/utils/fileHandler');
@@ -65,4 +66,15 @@ describe('ChangelogService', () => {
       'Changelog for version ## v1.1.0 already exists. Skipping.',
     );
   });
+
+  it('should throw FileNotFoundError if changelog file does not exist', async () => {
+    const changelogPath = 'CHANGELOG.md';
+    const error = new Error('File not found') as any;
+    error.code = 'ENOENT';
+    vi.spyOn(fileHandler, 'readFile').mockRejectedValue(error);
+
+    await expect(changelogService.updateChangelog('## v1.1.0\n\n- New feature')).rejects.toThrow(
+      new FileNotFoundError(`Changelog file not found at ${changelogPath}`),
+    );
+  });
 });