feat: skip PR comment when no changes; add disable-no-changes-comment flag

- Add `disable-no-changes-comment` action input (default: false) that, when
  enabled, suppresses the PR comment only when there are no module changes
  and no legacy tags/releases pending deletion
- Has no effect when there are changes to report — comments always post in
  that case

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Lee Trout

__tests__/config.test.ts

@@ -338,6 +338,7 @@ describe('config', () => {
       expect(config.disableWiki).toBe(false);
       expect(config.wikiSidebarChangelogMax).toBe(5);
       expect(config.disableBranding).toBe(false);
+      expect(config.disableNoChangesComment).toBe(false);
       expect(config.githubToken).toBe('ghp_test_token_2c6912E7710c838347Ae178B4');
       expect(config.modulePathIgnore).toEqual([]);
       expect(config.moduleChangeExcludePatterns).toEqual(['.gitignore', '*.md', '*.tftest.hcl', 'tests/**']);
@@ -365,6 +366,7 @@ describe('config', () => {
         ['Tag Directory Separator: /'],
         ['Use Version Prefix: true'],
         ['Module Ref Mode: tag'],
+        ['Disable No-Changes Comment: false'],
       ]);
     });
   });

__tests__/main.test.ts

@@ -63,6 +63,7 @@ describe('main', () => {
     context.isPrMergeEvent = false;
     config.disableWiki = false;
     config.deleteLegacyTags = true;
+    config.disableNoChangesComment = false;
 
     // Reset mocks with default values
     vi.mocked(hasReleaseComment).mockResolvedValue(false);
@@ -228,7 +229,38 @@ describe('main', () => {
       vi.mocked(TerraformModule.getTagsToDelete).mockReturnValue([]);
     });
 
-    it('should handle non-merge event (pull request event)', async () => {
+    it('should skip PR comment when no version changes and disable-no-changes-comment is true', async () => {
+      config.disableNoChangesComment = true;
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+
+      await run();
+
+      expect(addReleasePlanComment).not.toHaveBeenCalled();
+      expect(info).toHaveBeenCalledWith('No version changes detected. Skipping PR comment.');
+
+      // Should NOT call merge-specific functions
+      expect(createTaggedReleases).not.toHaveBeenCalled();
+      expect(addPostReleaseComment).not.toHaveBeenCalled();
+
+      // Should still set outputs
+      expect(setOutput).toHaveBeenCalled();
+    });
+
+    it('should skip PR comment when no module changes and delete-legacy-tags is disabled even with items to delete', async () => {
+      config.disableNoChangesComment = true;
+      config.deleteLegacyTags = false;
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+      vi.spyOn(TerraformModule, 'getReleasesToDelete').mockReturnValue([{ id: 1, title: 'old', body: '', tagName: 'modules/old/v0' }]);
+      vi.spyOn(TerraformModule, 'getTagsToDelete').mockReturnValue(['modules/old/v0']);
+
+      await run();
+
+      expect(addReleasePlanComment).not.toHaveBeenCalled();
+      expect(info).toHaveBeenCalledWith('No version changes detected. Skipping PR comment.');
+    });
+
+    it('should handle non-merge event (pull request event) when modules need release', async () => {
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([mockTerraformModuleNeedingRelease]);
       vi.mocked(getWikiStatus).mockReturnValue({ status: WIKI_STATUS.SUCCESS });
 
       await run();
@@ -250,7 +282,65 @@ describe('main', () => {
       expect(setOutput).toHaveBeenCalled();
     });
 
+    it('should comment when no modules need release but there are releases to delete', async () => {
+      const mockReleaseToDelete = { id: 99, title: 'old-release', body: '', tagName: 'old/v1.0.0' };
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+      vi.mocked(TerraformModule.getReleasesToDelete).mockReturnValue([mockReleaseToDelete]);
+      vi.mocked(getWikiStatus).mockReturnValue({ status: WIKI_STATUS.SUCCESS });
+
+      await run();
+
+      expect(addReleasePlanComment).toHaveBeenCalledWith([mockTerraformModule], [mockReleaseToDelete], [], {
+        status: WIKI_STATUS.SUCCESS,
+      });
+    });
+
+    it('should comment when no modules need release but there are tags to delete', async () => {
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+      vi.mocked(TerraformModule.getTagsToDelete).mockReturnValue(['old/v1.0.0']);
+      vi.mocked(getWikiStatus).mockReturnValue({ status: WIKI_STATUS.SUCCESS });
+
+      await run();
+
+      expect(addReleasePlanComment).toHaveBeenCalledWith([mockTerraformModule], [], ['old/v1.0.0'], {
+        status: WIKI_STATUS.SUCCESS,
+      });
+    });
+
+    it('should skip PR comment when disable-no-changes-comment is true and no changes', async () => {
+      config.disableNoChangesComment = true;
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+
+      await run();
+
+      expect(addReleasePlanComment).not.toHaveBeenCalled();
+      expect(info).toHaveBeenCalledWith('No version changes detected. Skipping PR comment.');
+    });
+
+    it('should still post PR comment when disable-no-changes-comment is true but modules need release', async () => {
+      config.disableNoChangesComment = true;
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([mockTerraformModuleNeedingRelease]);
+      vi.mocked(getWikiStatus).mockReturnValue({ status: WIKI_STATUS.SUCCESS });
+
+      await run();
+
+      expect(addReleasePlanComment).toHaveBeenCalled();
+    });
+
+    it('should still post PR comment when disable-no-changes-comment is true but there are legacy items to delete', async () => {
+      config.disableNoChangesComment = true;
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([]);
+      vi.mocked(TerraformModule.getReleasesToDelete).mockReturnValue([{ id: 99, title: 'old', body: '', tagName: 'old/v1.0.0' }]);
+      vi.mocked(getWikiStatus).mockReturnValue({ status: WIKI_STATUS.SUCCESS });
+
+      await run();
+
+      expect(addReleasePlanComment).toHaveBeenCalled();
+    });
+
     it('should handle wiki checkout errors and add release plan comment', async () => {
+      vi.mocked(TerraformModule.getModulesNeedingRelease).mockReturnValue([mockTerraformModuleNeedingRelease]);
+
       const mockError: ExecSyncError = Object.assign(new Error('Wiki checkout failed\nAdditional error details'), {
         name: 'ExecSyncError',
         pid: 12345,

__tests__/utils/metadata.test.ts

@@ -19,6 +19,7 @@ describe('utils/metadata', () => {
         'wiki-sidebar-changelog-max',
         'wiki-usage-template',
         'disable-branding',
+        'disable-no-changes-comment',
         'module-path-ignore',
         'module-change-exclude-patterns',
         'module-asset-exclude-patterns',
@@ -59,6 +60,7 @@ describe('utils/metadata', () => {
         'delete-legacy-tags',
         'disable-wiki',
         'disable-branding',
+        'disable-no-changes-comment',
         'use-ssh-source-format',
         'use-version-prefix',
       ];
@@ -130,6 +132,7 @@ describe('utils/metadata', () => {
         'wiki-sidebar-changelog-max': 'wikiSidebarChangelogMax',
         'wiki-usage-template': 'wikiUsageTemplate',
         'disable-branding': 'disableBranding',
+        'disable-no-changes-comment': 'disableNoChangesComment',
         'module-path-ignore': 'modulePathIgnore',
         'module-change-exclude-patterns': 'moduleChangeExcludePatterns',
         'module-asset-exclude-patterns': 'moduleAssetExcludePatterns',

action.yml

@@ -111,6 +111,13 @@ inputs:
       or where third-party branding is undesirable.
     required: true
     default: "false"
+  disable-no-changes-comment:
+    description: >
+      When set to true, suppresses the PR comment when there are no module changes and no legacy
+      tags/releases to delete. Has no effect when there are changes to report; comments are always
+      posted in that case. By default, this is false so a comment is always posted.
+    required: true
+    default: "false"
   module-path-ignore:
     description: >
       A comma-separated list of module paths to completely ignore during processing. Paths matching these patterns will