feat: Danger - Add inline changelog suggestions for GitHub PRs

Implements GitHub Issue #45 by replacing generic markdown instructions
with inline GitHub suggestions that users can apply with one click.

Changes:
- Add findChangelogInsertionPoint() to parse CHANGELOG.md structure
- Add generateChangelogSuggestion() to create formatted suggestions
- Update reportMissingChangelog() to use GitHub PR review comments API
- Maintain backward compatibility with fallback to markdown instructions
- Add comprehensive test suite (34 tests) covering edge cases

Users will now see precise inline suggestions instead of copy-paste
instructions, improving developer experience for changelog management.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: vaind

danger/dangerfile-utils.js

@@ -86,8 +86,95 @@ function extractPRFlavor(prTitle, prBranchRef) {
   return "";
 }
 
+/// Find insertion point for changelog entry in a specific section
+function findChangelogInsertionPoint(changelogContent, sectionName) {
+  const lines = changelogContent.split('\n');
+
+  // Find "## Unreleased" section
+  let unreleasedIndex = -1;
+  for (let i = 0; i < lines.length; i++) {
+    if (lines[i].trim().match(/^##\s+Unreleased/i)) {
+      unreleasedIndex = i;
+      break;
+    }
+  }
+
+  if (unreleasedIndex === -1) {
+    return null; // No Unreleased section found
+  }
+
+  // Find the target subsection (e.g., "### Features")
+  let sectionIndex = -1;
+  for (let i = unreleasedIndex + 1; i < lines.length; i++) {
+    // Stop if we hit another main section (##)
+    if (lines[i].trim().match(/^##\s+/)) {
+      break;
+    }
+
+    // Check for our target subsection
+    if (lines[i].trim().match(new RegExp(`^###\\s+${sectionName}`, 'i'))) {
+      sectionIndex = i;
+      break;
+    }
+  }
+
+  if (sectionIndex === -1) {
+    // Section doesn't exist, we need to create it
+    // Find insertion point after "## Unreleased"
+    let insertAfter = unreleasedIndex;
+
+    // Skip empty lines after "## Unreleased"
+    while (insertAfter + 1 < lines.length && lines[insertAfter + 1].trim() === '') {
+      insertAfter++;
+    }
+
+    return {
+      lineNumber: insertAfter + 1, // 1-indexed for GitHub API
+      createSection: true,
+      sectionName: sectionName
+    };
+  }
+
+  // Section exists, find first bullet point or insertion point
+  let insertionPoint = sectionIndex + 1;
+
+  // Skip empty lines after section header
+  while (insertionPoint < lines.length && lines[insertionPoint].trim() === '') {
+    insertionPoint++;
+  }
+
+  // If next line is a bullet point, insert before it
+  // If it's another section or end of file, insert here
+  return {
+    lineNumber: insertionPoint + 1, // 1-indexed for GitHub API
+    createSection: false
+  };
+}
+
+/// Generate suggestion text for changelog entry
+function generateChangelogSuggestion(prTitle, prNumber, prUrl, sectionName, insertionInfo) {
+  // Clean up PR title (remove conventional commit prefix if present)
+  const cleanTitle = prTitle
+    .split(": ")
+    .slice(-1)[0]
+    .trim()
+    .replace(/\.+$/, "");
+
+  const bulletPoint = `- ${cleanTitle} ([#${prNumber}](${prUrl}))`;
+
+  if (insertionInfo.createSection) {
+    // Need to create the section
+    return `\n### ${sectionName}\n\n${bulletPoint}`;
+  } else {
+    // Just add the bullet point
+    return bulletPoint;
+  }
+}
+
 module.exports = {
   FLAVOR_CONFIG,
   getFlavorConfig,
-  extractPRFlavor
+  extractPRFlavor,
+  findChangelogInsertionPoint,
+  generateChangelogSuggestion
 };

danger/dangerfile-utils.test.js

@@ -1,6 +1,6 @@
 const { describe, it } = require('node:test');
 const assert = require('node:assert');
-const { getFlavorConfig, extractPRFlavor, FLAVOR_CONFIG } = require('./dangerfile-utils.js');
+const { getFlavorConfig, extractPRFlavor, FLAVOR_CONFIG, findChangelogInsertionPoint, generateChangelogSuggestion } = require('./dangerfile-utils.js');
 
 describe('dangerfile-utils', () => {
   describe('getFlavorConfig', () => {
@@ -275,4 +275,240 @@ describe('dangerfile-utils', () => {
       });
     });
   });
+
+  describe('findChangelogInsertionPoint', () => {
+    it('should find insertion point for existing Features section', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+### Features
+
+- Existing feature ([#100](url))
+
+### Fixes
+
+- Existing fix ([#99](url))
+
+## 1.0.0
+
+Released content`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 7, // Before "- Existing feature"
+        createSection: false
+      });
+    });
+
+    it('should find insertion point when Features section exists but is empty', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+### Features
+
+### Fixes
+
+- Existing fix ([#99](url))`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 7, // Right after "### Features" and empty line
+        createSection: false
+      });
+    });
+
+    it('should create section when Features section does not exist', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+### Fixes
+
+- Existing fix ([#99](url))`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 4, // Right after "## Unreleased"
+        createSection: true,
+        sectionName: 'Features'
+      });
+    });
+
+    it('should handle changelog with only Unreleased section', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+## 1.0.0
+
+Released content`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 4, // Right after "## Unreleased"
+        createSection: true,
+        sectionName: 'Features'
+      });
+    });
+
+    it('should return null when no Unreleased section found', () => {
+      const changelog = `# Changelog
+
+## 1.0.0
+
+Released content`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.strictEqual(result, null);
+    });
+
+    it('should handle case-insensitive Unreleased section', () => {
+      const changelog = `# Changelog
+
+## unreleased
+
+### Features
+
+- Existing feature ([#100](url))`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 7,
+        createSection: false
+      });
+    });
+
+    it('should handle different section names', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+### Security
+
+- Security fix ([#101](url))`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Fixes');
+      assert.deepStrictEqual(result, {
+        lineNumber: 4, // After "## Unreleased"
+        createSection: true,
+        sectionName: 'Fixes'
+      });
+    });
+
+    it('should handle extra whitespace around sections', () => {
+      const changelog = `# Changelog
+
+## Unreleased
+
+   ### Features
+
+   - Existing feature ([#100](url))`;
+
+      const result = findChangelogInsertionPoint(changelog, 'Features');
+      assert.deepStrictEqual(result, {
+        lineNumber: 7, // Before "   - Existing feature"
+        createSection: false
+      });
+    });
+  });
+
+  describe('generateChangelogSuggestion', () => {
+    it('should generate bullet point for existing section', () => {
+      const insertionInfo = { lineNumber: 7, createSection: false };
+      const result = generateChangelogSuggestion(
+        'feat: add new feature',
+        123,
+        'https://github.com/repo/pull/123',
+        'Features',
+        insertionInfo
+      );
+
+      assert.strictEqual(result, '- add new feature ([#123](https://github.com/repo/pull/123))');
+    });
+
+    it('should generate section with bullet point for new section', () => {
+      const insertionInfo = { lineNumber: 4, createSection: true, sectionName: 'Features' };
+      const result = generateChangelogSuggestion(
+        'feat: add new feature',
+        123,
+        'https://github.com/repo/pull/123',
+        'Features',
+        insertionInfo
+      );
+
+      assert.strictEqual(result, '\n### Features\n\n- add new feature ([#123](https://github.com/repo/pull/123))');
+    });
+
+    it('should clean up PR title by removing conventional commit prefix', () => {
+      const insertionInfo = { lineNumber: 7, createSection: false };
+
+      const result1 = generateChangelogSuggestion(
+        'feat(auth): add OAuth support',
+        123,
+        'url',
+        'Features',
+        insertionInfo
+      );
+      assert.strictEqual(result1, '- add OAuth support ([#123](url))');
+
+      const result2 = generateChangelogSuggestion(
+        'fix: resolve memory leak',
+        124,
+        'url',
+        'Fixes',
+        insertionInfo
+      );
+      assert.strictEqual(result2, '- resolve memory leak ([#124](url))');
+    });
+
+    it('should handle non-conventional PR titles', () => {
+      const insertionInfo = { lineNumber: 7, createSection: false };
+
+      const result = generateChangelogSuggestion(
+        'Fix memory leak in authentication',
+        125,
+        'url',
+        'Fixes',
+        insertionInfo
+      );
+      assert.strictEqual(result, '- Fix memory leak in authentication ([#125](url))');
+    });
+
+    it('should remove trailing periods from title', () => {
+      const insertionInfo = { lineNumber: 7, createSection: false };
+
+      const result = generateChangelogSuggestion(
+        'feat: add new feature...',
+        126,
+        'url',
+        'Features',
+        insertionInfo
+      );
+      assert.strictEqual(result, '- add new feature ([#126](url))');
+    });
+
+    it('should handle various section names', () => {
+      const insertionInfo = { lineNumber: 4, createSection: true };
+
+      const securityResult = generateChangelogSuggestion(
+        'sec: fix vulnerability',
+        127,
+        'url',
+        'Security',
+        insertionInfo
+      );
+      assert.strictEqual(securityResult, '\n### Security\n\n- fix vulnerability ([#127](url))');
+
+      const perfResult = generateChangelogSuggestion(
+        'perf: optimize queries',
+        128,
+        'url',
+        'Performance',
+        insertionInfo
+      );
+      assert.strictEqual(perfResult, '\n### Performance\n\n- optimize queries ([#128](url))');
+    });
+  });
 });