fix: handle empty responses from Gemini API

- Add tracking for whether any text content was yielded
- Throw specific error when Gemini API returns empty response
- Add translation keys for empty response error in English and Chinese
- Add test coverage for empty response scenario

Fixes #7046

Author: roomote

src/api/providers/__tests__/gemini.spec.ts

@@ -90,6 +90,24 @@ describe("GeminiHandler", () => {
 			)
 		})
 
+		it("should handle empty response from API", async () => {
+			// Setup the mock to return an async generator with no text content
+			;(handler["client"].models.generateContentStream as any).mockResolvedValue({
+				[Symbol.asyncIterator]: async function* () {
+					// Yield only usage metadata, no text content
+					yield { usageMetadata: { promptTokenCount: 10, candidatesTokenCount: 0 } }
+				},
+			})
+
+			const stream = handler.createMessage(systemPrompt, mockMessages)
+
+			await expect(async () => {
+				for await (const _chunk of stream) {
+					// Should throw before yielding any chunks
+				}
+			}).rejects.toThrow(t("common:errors.gemini.generate_stream"))
+		})
+
 		it("should handle API errors", async () => {
 			const mockError = new Error("Gemini API error")
 			;(handler["client"].models.generateContentStream as any).mockRejectedValue(mockError)

src/api/providers/gemini.ts

@@ -94,6 +94,7 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 
 			let lastUsageMetadata: GenerateContentResponseUsageMetadata | undefined
 			let pendingGroundingMetadata: GroundingMetadata | undefined
+			let hasYieldedContent = false // Track if we've yielded any text content
 
 			for await (const chunk of result) {
 				// Process candidates and their parts to separate thoughts from content
@@ -115,6 +116,7 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 								// This is regular content
 								if (part.text) {
 									yield { type: "text", text: part.text }
+									hasYieldedContent = true
 								}
 							}
 						}
@@ -124,13 +126,27 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 				// Fallback to the original text property if no candidates structure
 				else if (chunk.text) {
 					yield { type: "text", text: chunk.text }
+					hasYieldedContent = true
 				}
 
 				if (chunk.usageMetadata) {
 					lastUsageMetadata = chunk.usageMetadata
 				}
 			}
 
+			// Check if we got an empty response
+			if (!hasYieldedContent) {
+				// Log the issue for debugging
+				console.warn("Gemini API returned empty response, no text content was generated")
+
+				// Throw a specific error that can be caught and retried
+				throw new Error(
+					t("common:errors.gemini.empty_response", {
+						error: "The Gemini API did not return any text content. This may be a temporary issue.",
+					}),
+				)
+			}
+
 			if (pendingGroundingMetadata) {
 				const citations = this.extractCitationsOnly(pendingGroundingMetadata)
 				if (citations) {

src/i18n/locales/en/common.json

@@ -90,7 +90,8 @@
 		"gemini": {
 			"generate_stream": "Gemini generate context stream error: {{error}}",
 			"generate_complete_prompt": "Gemini completion error: {{error}}",
-			"sources": "Sources:"
+			"sources": "Sources:",
+			"empty_response": "Gemini API returned empty response: {{error}}"
 		},
 		"cerebras": {
 			"authenticationFailed": "Cerebras API authentication failed. Please check your API key is valid and not expired.",