fix: enhance error handling for Firestore queries and improve test validations

- Added special handling for Firebase index errors in the query error response, providing a clear message and a link to create the required composite index.
- Updated tests to filter and verify the presence of specific test documents instead of checking total count, ensuring more accurate validation of query results.

Author: gannonh

src/index.ts

@@ -831,11 +831,29 @@ class FirebaseMcpServer {
               };
             } catch (error) {
               logger.error('Error in collection group query:', error);
+              
+              // Special handling for Firebase index errors
+              const errorMessage = error instanceof Error ? error.message : 'Unknown error';
+              if (errorMessage.includes('FAILED_PRECONDITION') && errorMessage.includes('requires an index')) {
+                const indexUrl = errorMessage.match(/https:\/\/console\.firebase\.google\.com[^\s]*/)?.[0];
+                return {
+                  content: [{
+                    type: 'text',
+                    text: JSON.stringify({
+                      error: 'This query requires a composite index.',
+                      details: 'When ordering by multiple fields or combining filters with ordering, you need to create a composite index.',
+                      indexUrl: indexUrl || null,
+                      message: errorMessage
+                    })
+                  }]
+                };
+              }
+              
               return {
                 content: [{
                   type: 'text',
                   text: JSON.stringify({
-                    error: error instanceof Error ? error.message : 'Unknown error'
+                    error: errorMessage
                   })
                 }]
               };

src/lib/firebase/__tests__/firestoreClient.test.ts

@@ -747,13 +747,21 @@ describe('Firestore Client', () => {
         // Parse the response
         const responseData = JSON.parse(result.content[0].text);
 
-        // Verify documents array exists and has correct length
+        // Verify documents array exists
         expect(Array.isArray(responseData.documents)).toBe(true);
-        expect(responseData.documents.length).toBe(2); // Should find both comments
+        
+        // Instead of checking total count, filter to only include our test documents
+        const testDocuments = responseData.documents.filter((doc: any) => 
+          doc.path.includes(`${testCollection}/${parentDoc1Id}/${subcollectionName}`) || 
+          doc.path.includes(`${testCollection}/${parentDoc2Id}/${subcollectionName}`)
+        );
+        
+        // Verify we have our 2 test documents
+        expect(testDocuments.length).toBe(2);
 
         // Verify both documents are returned with correct data
-        const document1 = responseData.documents.find((doc: any) => doc.id === 'comment1');
-        const document2 = responseData.documents.find((doc: any) => doc.id === 'comment2');
+        const document1 = testDocuments.find((doc: any) => doc.id === 'comment1');
+        const document2 = testDocuments.find((doc: any) => doc.id === 'comment2');
 
         expect(document1).toBeDefined();
         expect(document1.data.author).toBe('User A');