fix(core): combine .gitignore and .geminiignore logic for correct precedence (#11587)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/core/src/services/fileDiscoveryService.test.ts

@@ -245,4 +245,87 @@ describe('FileDiscoveryService', () => {
       ]);
     });
   });
+  describe('precedence (.geminiignore over .gitignore)', () => {
+    beforeEach(async () => {
+      await fs.mkdir(path.join(projectRoot, '.git'));
+    });
+
+    it('should un-ignore a file in .geminiignore that is ignored in .gitignore', async () => {
+      await createTestFile('.gitignore', '*.txt');
+      await createTestFile('.geminiignore', '!important.txt');
+
+      const service = new FileDiscoveryService(projectRoot);
+      const files = ['file.txt', 'important.txt'].map((f) =>
+        path.join(projectRoot, f),
+      );
+
+      const filtered = service.filterFiles(files);
+      expect(filtered).toEqual([path.join(projectRoot, 'important.txt')]);
+    });
+
+    it('should un-ignore a directory in .geminiignore that is ignored in .gitignore', async () => {
+      await createTestFile('.gitignore', 'logs/');
+      await createTestFile('.geminiignore', '!logs/');
+
+      const service = new FileDiscoveryService(projectRoot);
+      const files = ['logs/app.log', 'other/app.log'].map((f) =>
+        path.join(projectRoot, f),
+      );
+
+      const filtered = service.filterFiles(files);
+      expect(filtered).toEqual(files);
+    });
+
+    it('should extend ignore rules in .geminiignore', async () => {
+      await createTestFile('.gitignore', '*.log');
+      await createTestFile('.geminiignore', 'temp/');
+
+      const service = new FileDiscoveryService(projectRoot);
+      const files = ['app.log', 'temp/file.txt'].map((f) =>
+        path.join(projectRoot, f),
+      );
+
+      const filtered = service.filterFiles(files);
+      expect(filtered).toEqual([]);
+    });
+
+    it('should use .gitignore rules if respectGeminiIgnore is false', async () => {
+      await createTestFile('.gitignore', '*.txt');
+      await createTestFile('.geminiignore', '!important.txt');
+
+      const service = new FileDiscoveryService(projectRoot);
+      const files = ['file.txt', 'important.txt'].map((f) =>
+        path.join(projectRoot, f),
+      );
+
+      const filtered = service.filterFiles(files, {
+        respectGitIgnore: true,
+        respectGeminiIgnore: false,
+      });
+
+      expect(filtered).toEqual([]);
+    });
+
+    it('should use .geminiignore rules if respectGitIgnore is false', async () => {
+      await createTestFile('.gitignore', '*.txt');
+      await createTestFile('.geminiignore', '!important.txt\ntemp/');
+
+      const service = new FileDiscoveryService(projectRoot);
+      const files = ['file.txt', 'important.txt', 'temp/file.js'].map((f) =>
+        path.join(projectRoot, f),
+      );
+
+      const filtered = service.filterFiles(files, {
+        respectGitIgnore: false,
+        respectGeminiIgnore: true,
+      });
+
+      // .gitignore is ignored, so *.txt is not applied.
+      // .geminiignore un-ignores important.txt (which wasn't ignored anyway)
+      // and ignores temp/
+      expect(filtered).toEqual(
+        ['file.txt', 'important.txt'].map((f) => path.join(projectRoot, f)),
+      );
+    });
+  });
 });

packages/core/src/services/fileDiscoveryService.ts

@@ -24,6 +24,7 @@ export interface FilterReport {
 export class FileDiscoveryService {
   private gitIgnoreFilter: GitIgnoreFilter | null = null;
   private geminiIgnoreFilter: GeminiIgnoreFilter | null = null;
+  private combinedIgnoreFilter: GitIgnoreFilter | null = null;
   private projectRoot: string;
 
   constructor(projectRoot: string) {
@@ -32,6 +33,15 @@ export class FileDiscoveryService {
       this.gitIgnoreFilter = new GitIgnoreParser(this.projectRoot);
     }
     this.geminiIgnoreFilter = new GeminiIgnoreParser(this.projectRoot);
+
+    if (this.gitIgnoreFilter) {
+      const geminiPatterns = this.geminiIgnoreFilter.getPatterns();
+      // Create combined parser: .gitignore + .geminiignore
+      this.combinedIgnoreFilter = new GitIgnoreParser(
+        this.projectRoot,
+        geminiPatterns,
+      );
+    }
   }
 
   /**
@@ -40,6 +50,14 @@ export class FileDiscoveryService {
   filterFiles(filePaths: string[], options: FilterFilesOptions = {}): string[] {
     const { respectGitIgnore = true, respectGeminiIgnore = true } = options;
     return filePaths.filter((filePath) => {
+      if (
+        respectGitIgnore &&
+        respectGeminiIgnore &&
+        this.combinedIgnoreFilter
+      ) {
+        return !this.combinedIgnoreFilter.isIgnored(filePath);
+      }
+
       if (respectGitIgnore && this.gitIgnoreFilter?.isIgnored(filePath)) {
         return false;
       }