core[patch]: Treat OpenAI message format as a message like (#6654)

langchain-core/src/language_models/tests/chat_models.test.ts

@@ -27,6 +27,64 @@ test("Test ChatModel accepts object shorthand for messages", async () => {
   expect(response.content).toEqual("Hello there!");
 });
 
+test("Test ChatModel accepts object with role for messages", async () => {
+  const model = new FakeChatModel({});
+  const response = await model.invoke([
+    {
+      role: "human",
+      content: "Hello there!!",
+      example: true,
+    },
+  ]);
+  expect(response.content).toEqual("Hello there!!");
+});
+
+test("Test ChatModel accepts several messages as objects with role", async () => {
+  const model = new FakeChatModel({});
+  const response = await model.invoke([
+    {
+      role: "system",
+      content: "You are an assistant.",
+    },
+    {
+      role: "human",
+      content: [{ type: "text", text: "What is the weather in SF?" }],
+      example: true,
+    },
+    {
+      role: "assistant",
+      content: "",
+      tool_calls: [
+        {
+          id: "call_123",
+          function: {
+            name: "get_weather",
+            arguments: JSON.stringify({ location: "sf" }),
+          },
+          type: "function",
+        },
+      ],
+    },
+    {
+      role: "tool",
+      content: "Pretty nice right now!",
+      tool_call_id: "call_123",
+    },
+  ]);
+  expect(response.content).toEqual(
+    [
+      "You are an assistant.",
+      JSON.stringify(
+        [{ type: "text", text: "What is the weather in SF?" }],
+        null,
+        2
+      ),
+      "",
+      "Pretty nice right now!",
+    ].join("\n")
+  );
+});
+
 test("Test ChatModel uses callbacks", async () => {
   const model = new FakeChatModel({});
   let acc = "";

langchain-core/src/messages/base.ts

@@ -450,12 +450,25 @@ export abstract class BaseMessageChunk extends BaseMessage {
   abstract concat(chunk: BaseMessageChunk): BaseMessageChunk;
 }
 
+export type MessageFieldWithRole = {
+  role: StringWithAutocomplete<"user" | "assistant" | MessageType>;
+  content: MessageContent;
+  name?: string;
+} & Record<string, unknown>;
+
+export function _isMessageFieldWithRole(
+  x: BaseMessageLike
+): x is MessageFieldWithRole {
+  return typeof (x as MessageFieldWithRole).role === "string";
+}
+
 export type BaseMessageLike =
   | BaseMessage
   | ({
       type: MessageType | "user" | "assistant" | "placeholder";
     } & BaseMessageFields &
       Record<string, unknown>)
+  | MessageFieldWithRole
   | [
       StringWithAutocomplete<
         MessageType | "user" | "assistant" | "placeholder"

langchain-core/src/messages/tests/base_message.test.ts

@@ -6,6 +6,8 @@ import {
   ToolMessage,
   ToolMessageChunk,
   AIMessageChunk,
+  coerceMessageLikeToMessage,
+  SystemMessage,
 } from "../index.js";
 import { load } from "../../load/index.js";
 
@@ -334,3 +336,63 @@ describe("Complex AIMessageChunk concat", () => {
     );
   });
 });
+
+describe("Message like coercion", () => {
+  it("Should convert OpenAI format messages", async () => {
+    const messages = [
+      {
+        id: "foobar",
+        role: "system",
+        content: "6",
+      },
+      {
+        role: "user",
+        content: [{ type: "image_url", image_url: { url: "7.1" } }],
+      },
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "8.1" }],
+        tool_calls: [
+          {
+            id: "8.5",
+            function: {
+              name: "8.4",
+              arguments: JSON.stringify({ "8.2": "8.3" }),
+            },
+            type: "function",
+          },
+        ],
+      },
+      {
+        role: "tool",
+        content: "10.2",
+        tool_call_id: "10.2",
+      },
+    ].map(coerceMessageLikeToMessage);
+    expect(messages).toEqual([
+      new SystemMessage({
+        id: "foobar",
+        content: "6",
+      }),
+      new HumanMessage({
+        content: [{ type: "image_url", image_url: { url: "7.1" } }],
+      }),
+      new AIMessage({
+        content: [{ type: "text", text: "8.1" }],
+        tool_calls: [
+          {
+            id: "8.5",
+            name: "8.4",
+            args: { "8.2": "8.3" },
+            type: "tool_call",
+          },
+        ],
+      }),
+      new ToolMessage({
+        name: undefined,
+        content: "10.2",
+        tool_call_id: "10.2",
+      }),
+    ]);
+  });
+});

langchain-core/src/messages/utils.ts

@@ -1,3 +1,4 @@
+import { _isToolCall } from "../tools/utils.js";
 import { AIMessage, AIMessageChunk, AIMessageChunkFields } from "./ai.js";
 import {
   BaseMessageLike,
@@ -6,6 +7,7 @@ import {
   StoredMessage,
   StoredMessageV1,
   BaseMessageFields,
+  _isMessageFieldWithRole,
 } from "./base.js";
 import {
   ChatMessage,
@@ -19,16 +21,53 @@ import {
 } from "./function.js";
 import { HumanMessage, HumanMessageChunk } from "./human.js";
 import { SystemMessage, SystemMessageChunk } from "./system.js";
-import { ToolMessage, ToolMessageFieldsWithToolCallId } from "./tool.js";
+import {
+  ToolCall,
+  ToolMessage,
+  ToolMessageFieldsWithToolCallId,
+} from "./tool.js";
+
+function _coerceToolCall(
+  toolCall: ToolCall | Record<string, unknown>
+): ToolCall {
+  if (_isToolCall(toolCall)) {
+    return toolCall;
+  } else if (
+    typeof toolCall.id === "string" &&
+    toolCall.type === "function" &&
+    typeof toolCall.function === "object" &&
+    toolCall.function !== null &&
+    "arguments" in toolCall.function &&
+    typeof toolCall.function.arguments === "string" &&
+    "name" in toolCall.function &&
+    typeof toolCall.function.name === "string"
+  ) {
+    // Handle OpenAI tool call format
+    return {
+      id: toolCall.id,
+      args: JSON.parse(toolCall.function.arguments),
+      name: toolCall.function.name,
+      type: "tool_call",
+    };
+  } else {
+    // TODO: Throw an error?
+    return toolCall as ToolCall;
+  }
+}
 
 function _constructMessageFromParams(
-  params: BaseMessageFields & { type: string }
+  params: BaseMessageFields & { type: string } & Record<string, unknown>
 ) {
   const { type, ...rest } = params;
   if (type === "human" || type === "user") {
     return new HumanMessage(rest);
   } else if (type === "ai" || type === "assistant") {
-    return new AIMessage(rest);
+    const { tool_calls: rawToolCalls, ...other } = rest;
+    if (!Array.isArray(rawToolCalls)) {
+      return new AIMessage(rest);
+    }
+    const tool_calls = rawToolCalls.map(_coerceToolCall);
+    return new AIMessage({ ...other, tool_calls });
   } else if (type === "system") {
     return new SystemMessage(rest);
   } else if (type === "tool" && "tool_call_id" in rest) {
@@ -56,6 +95,9 @@ export function coerceMessageLikeToMessage(
   if (Array.isArray(messageLike)) {
     const [type, content] = messageLike;
     return _constructMessageFromParams({ type, content });
+  } else if (_isMessageFieldWithRole(messageLike)) {
+    const { role: type, ...rest } = messageLike;
+    return _constructMessageFromParams({ ...rest, type });
   } else {
     return _constructMessageFromParams(messageLike);
   }