fix(groq): Support generic messages in messageToGroqRole (langchain-ai#8917)

Author: christian-bromann

.changeset/honest-fireants-greet.md

@@ -0,0 +1,5 @@
+---
+"@langchain/groq": patch
+---
+
+fix(groq): Support generic messages in messageToGroqRole

libs/langchain-groq/src/chat_models.ts

@@ -292,8 +292,32 @@ interface TokenUsage {
   totalTokens?: number;
 }
 
+/**
+ * Extract the custom role from a message.
+ * @param message - The message to extract the custom role from.
+ * @returns The custom role of the message.
+ */
+function extractGenericMessageCustomRole(message: ChatMessage): GroqRoleEnum {
+  if (
+    message.role !== "system" &&
+    message.role !== "assistant" &&
+    message.role !== "user" &&
+    message.role !== "function"
+  ) {
+    throw new Error(
+      `Unsupported message role: ${message.role}. Expected "system", "assistant", "user", or "function"`
+    );
+  }
+  return message.role as GroqRoleEnum;
+}
+
+/**
+ * Extract the role from a message.
+ * @param message - The message to extract the role from.
+ * @returns The role of the message.
+ */
 export function messageToGroqRole(message: BaseMessage): GroqRoleEnum {
-  const type = message._getType();
+  const type = message.getType();
   switch (type) {
     case "system":
       return "system";
@@ -306,6 +330,11 @@ export function messageToGroqRole(message: BaseMessage): GroqRoleEnum {
     case "tool":
       // Not yet supported as a type
       return "tool" as GroqRoleEnum;
+    case "generic": {
+      if (!ChatMessage.isInstance(message))
+        throw new Error("Invalid generic chat message");
+      return extractGenericMessageCustomRole(message);
+    }
     default:
       throw new Error(`Unknown message type: ${type}`);
   }

libs/langchain-groq/src/tests/chat_models.test.ts

@@ -1,6 +1,8 @@
 /* eslint-disable no-process-env */
 import { test, expect } from "@jest/globals";
-import { ChatGroq } from "../chat_models.js";
+import { ChatMessage } from "@langchain/core/messages";
+
+import { ChatGroq, messageToGroqRole } from "../chat_models.js";
 
 test("Serialization", () => {
   const model = new ChatGroq({
@@ -11,3 +13,37 @@ test("Serialization", () => {
     `{"lc":1,"type":"constructor","id":["langchain","chat_models","groq","ChatGroq"],"kwargs":{"api_key":{"lc":1,"type":"secret","id":["GROQ_API_KEY"]},"model":"llama-3.3-70b-versatile"}}`
   );
 });
+
+test("messageToGroqRole", () => {
+  // Test generic messages (ChatMessage type = "generic") with valid roles
+  // These test the extractGenericMessageCustomRole path
+  const genericUser = new ChatMessage("Hello, world!", "user");
+  expect(messageToGroqRole(genericUser)).toBe("user");
+
+  const genericAssistant = new ChatMessage("Hello, world!", "assistant");
+  expect(messageToGroqRole(genericAssistant)).toBe("assistant");
+
+  const genericSystem = new ChatMessage("Hello, world!", "system");
+  expect(messageToGroqRole(genericSystem)).toBe("system");
+
+  const genericFunction = new ChatMessage("Hello, world!", "function");
+  expect(messageToGroqRole(genericFunction)).toBe("function");
+
+  // Test generic message with tool role - should throw via extractGenericMessageCustomRole
+  const genericTool = new ChatMessage("Hello, world!", "tool");
+  expect(() => messageToGroqRole(genericTool)).toThrow(
+    'Unsupported message role: tool. Expected "system", "assistant", "user", or "function"'
+  );
+
+  // Test generic message with invalid role - should throw via extractGenericMessageCustomRole
+  const genericInvalid = new ChatMessage("Invalid message", "invalid");
+  expect(() => messageToGroqRole(genericInvalid)).toThrow(
+    'Unsupported message role: invalid. Expected "system", "assistant", "user", or "function"'
+  );
+
+  // Test generic message with custom role that's not supported
+  const genericCustom = new ChatMessage("Custom message", "custom-role");
+  expect(() => messageToGroqRole(genericCustom)).toThrow(
+    'Unsupported message role: custom-role. Expected "system", "assistant", "user", or "function"'
+  );
+});