google-common [feature]: Support JSON Mode for Gemini #5071 (#5190)

* google-common [feature]: Support JSON Mode for Gemini #5071

* added mock json file for tests

* defined GoogleAIResponseMimeType type

* responseMimetype default specified in the GoogleBaseLLM class that implements it

* test to make sure the request contains the responseMimeType setting in the generation config

* Format llms.test.ts

* Format llms.ts

* Format types.ts

* Nit types.ts jsdoc

* Format types.ts

---------

Co-authored-by: GiacomoCherry <[email protected]>
Co-authored-by: Brace Sproul <[email protected]>

Author: 3 people

libs/langchain-google-common/src/connection.ts

@@ -282,6 +282,7 @@ export abstract class AbstractGoogleLLMConnection<
       topP: parameters.topP,
       maxOutputTokens: parameters.maxOutputTokens,
       stopSequences: parameters.stopSequences,
+      responseMimeType: parameters.responseMimeType,
     };
   }
 

libs/langchain-google-common/src/llms.ts

@@ -15,6 +15,7 @@ import {
   GoogleAISafetySetting,
   GooglePlatformType,
   GeminiContent,
+  GoogleAIResponseMimeType,
 } from "./types.js";
 import {
   copyAIModelParams,
@@ -103,6 +104,8 @@ export abstract class GoogleBaseLLM<AuthOptions>
 
   safetyHandler: GoogleAISafetyHandler;
 
+  responseMimeType: GoogleAIResponseMimeType = "text/plain";
+
   protected connection: GoogleLLMConnection<AuthOptions>;
 
   protected streamedConnection: GoogleLLMConnection<AuthOptions>;