Beef up tool message support

langchain-core/.gitignore

@@ -62,6 +62,10 @@ messages.cjs
 messages.js
 messages.d.ts
 messages.d.cts
+messages/tool.cjs
+messages/tool.js
+messages/tool.d.ts
+messages/tool.d.cts
 output_parsers.cjs
 output_parsers.js
 output_parsers.d.ts

langchain-core/langchain.config.js

@@ -28,6 +28,7 @@ export const config = {
     "load/serializable": "load/serializable",
     memory: "memory",
     messages: "messages/index",
+    "messages/tool": "messages/tool",
     output_parsers: "output_parsers/index",
     "output_parsers/openai_tools": "output_parsers/openai_tools/index",
     "output_parsers/openai_functions": "output_parsers/openai_functions/index",

langchain-core/package.json

@@ -237,6 +237,15 @@
       "import": "./messages.js",
       "require": "./messages.cjs"
     },
+    "./messages/tool": {
+      "types": {
+        "import": "./messages/tool.d.ts",
+        "require": "./messages/tool.d.cts",
+        "default": "./messages/tool.d.ts"
+      },
+      "import": "./messages/tool.js",
+      "require": "./messages/tool.cjs"
+    },
     "./output_parsers": {
       "types": {
         "import": "./output_parsers.d.ts",
@@ -620,6 +629,10 @@
     "messages.js",
     "messages.d.ts",
     "messages.d.cts",
+    "messages/tool.cjs",
+    "messages/tool.js",
+    "messages/tool.d.ts",
+    "messages/tool.d.cts",
     "output_parsers.cjs",
     "output_parsers.js",
     "output_parsers.d.ts",

langchain-core/src/messages/ai.ts

@@ -0,0 +1,145 @@
+import { parsePartialJson } from "../output_parsers/json.js";
+import {
+  BaseMessage,
+  BaseMessageChunk,
+  mergeContent,
+  _mergeDicts,
+  type MessageType,
+  BaseMessageFields,
+} from "./base.js";
+import {
+  InvalidToolCall,
+  ToolCall,
+  ToolCallChunk,
+  defaultToolCallParser,
+} from "./tool.js";
+
+export type AIMessageFields = BaseMessageFields & {
+  tool_calls?: (ToolCall | InvalidToolCall)[];
+};
+
+/**
+ * Represents an AI message in a conversation.
+ */
+export class AIMessage extends BaseMessage {
+  tool_calls?: (ToolCall | InvalidToolCall)[];
+
+  get lc_aliases(): Record<string, string> {
+    // exclude snake case conversion to pascal case
+    return {
+      ...super.lc_aliases,
+      tool_calls: "tool_calls",
+    };
+  }
+
+  constructor(fields: string | AIMessageFields) {
+    if (typeof fields === "string") {
+      super(fields);
+      return;
+    }
+    try {
+      const rawToolCalls = fields.additional_kwargs?.tool_calls;
+      const toolCalls = fields.tool_calls;
+      if (rawToolCalls !== undefined && toolCalls === undefined) {
+        // eslint-disable-next-line no-param-reassign
+        fields.tool_calls = defaultToolCallParser(rawToolCalls ?? []);
+      }
+    } catch (e) {
+      // Do nothing if parsing fails
+    }
+    super(fields);
+    this.tool_calls = fields.tool_calls;
+  }
+
+  static lc_name() {
+    return "AIMessage";
+  }
+
+  _getType(): MessageType {
+    return "ai";
+  }
+}
+
+export type AIMessageChunkFields = AIMessageFields & {
+  tool_call_chunks?: ToolCallChunk[];
+};
+
+/**
+ * Represents a chunk of an AI message, which can be concatenated with
+ * other AI message chunks.
+ */
+export class AIMessageChunk extends BaseMessageChunk {
+  // Must redeclare "tool_calls" field due to lack of support for multiple inhertiance.
+  tool_calls?: (ToolCall | InvalidToolCall)[];
+
+  tool_call_chunks?: ToolCallChunk[];
+
+  constructor(fields: AIMessageChunkFields) {
+    if (fields.tool_calls !== undefined) {
+      throw new Error(
+        `"tool_calls" cannot be set directly on AIMessageChunk, it is derived from "tool_call_chunks".`
+      );
+    }
+    if (
+      fields.tool_call_chunks === undefined ||
+      fields.tool_call_chunks.length === 0
+    ) {
+      super({ tool_calls: fields.tool_call_chunks, ...fields });
+    } else {
+      // eslint-disable-next-line no-param-reassign
+      fields.tool_calls = fields.tool_call_chunks.map((toolCallChunk) => {
+        let parsedArgs = {};
+        try {
+          parsedArgs = parsePartialJson(toolCallChunk.args ?? "{}") ?? {};
+        } catch (e) {
+          // Do nothing if parsing fails
+        }
+        return new ToolCall({
+          name: toolCallChunk.name ?? "",
+          args: parsedArgs,
+          index: toolCallChunk.index,
+          id: toolCallChunk.id,
+        });
+      });
+    }
+    super(fields);
+    this.tool_call_chunks = fields.tool_call_chunks;
+    this.tool_calls = fields.tool_calls;
+  }
+
+  get lc_aliases(): Record<string, string> {
+    // exclude snake case conversion to pascal case
+    return {
+      ...super.lc_aliases,
+      tool_call_chunks: "tool_call_chunks",
+    };
+  }
+
+  static lc_name() {
+    return "AIMessageChunk";
+  }
+
+  _getType(): MessageType {
+    return "ai";
+  }
+
+  concat(chunk: AIMessageChunk) {
+    const combinedFields: AIMessageChunkFields = {
+      content: mergeContent(this.content, chunk.content),
+      additional_kwargs: _mergeDicts(
+        this.additional_kwargs,
+        chunk.additional_kwargs
+      ),
+      response_metadata: _mergeDicts(
+        this.response_metadata,
+        chunk.response_metadata
+      ),
+    };
+    if (
+      this.tool_call_chunks !== undefined ||
+      chunk.tool_call_chunks !== undefined
+    ) {
+    }
+    return new AIMessageChunk(combinedFields);
+  }
+}