core[patch]: Improve console.log format for messages (#6121)

* Improve console.log format for messages

* Fix lint

* Fix console.dir case

langchain-core/src/messages/ai.ts

@@ -128,6 +128,15 @@ export class AIMessage extends BaseMessage {
   _getType(): MessageType {
     return "ai";
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      tool_calls: this.tool_calls,
+      invalid_tool_calls: this.invalid_tool_calls,
+      usage_metadata: this.usage_metadata,
+    };
+  }
 }
 
 export function isAIMessage(x: BaseMessage): x is AIMessage {
@@ -234,6 +243,16 @@ export class AIMessageChunk extends BaseMessageChunk {
     return "ai";
   }
 
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      tool_calls: this.tool_calls,
+      tool_call_chunks: this.tool_call_chunks,
+      invalid_tool_calls: this.invalid_tool_calls,
+      usage_metadata: this.usage_metadata,
+    };
+  }
+
   concat(chunk: AIMessageChunk) {
     const combinedFields: AIMessageChunkFields = {
       content: mergeContent(this.content, chunk.content),

langchain-core/src/messages/base.ts

@@ -140,6 +140,34 @@ export function mergeContent(
   }
 }
 
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function stringifyWithDepthLimit(obj: any, depthLimit: number): string {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  function helper(obj: any, currentDepth: number): any {
+    if (typeof obj !== "object" || obj === null || obj === undefined) {
+      return obj;
+    }
+    if (currentDepth >= depthLimit) {
+      if (Array.isArray(obj)) {
+        return "[Array]";
+      }
+      return "[Object]";
+    }
+
+    if (Array.isArray(obj)) {
+      return obj.map((item) => helper(item, currentDepth + 1));
+    }
+
+    const result: Record<string, unknown> = {};
+    for (const key of Object.keys(obj)) {
+      result[key] = helper(obj[key], currentDepth + 1);
+    }
+    return result;
+  }
+
+  return JSON.stringify(helper(obj, 0), null, 2);
+}
+
 /**
  * Base class for all types of messages in a conversation. It includes
  * properties like `content`, `name`, and `additional_kwargs`. It also
@@ -227,6 +255,39 @@ export abstract class BaseMessage
         .kwargs as StoredMessageData,
     };
   }
+
+  static lc_name() {
+    return "BaseMessage";
+  }
+
+  // Can't be protected for silly reasons
+  get _printableFields(): Record<string, unknown> {
+    return {
+      id: this.id,
+      content: this.content,
+      name: this.name,
+      additional_kwargs: this.additional_kwargs,
+      response_metadata: this.response_metadata,
+    };
+  }
+
+  get [Symbol.toStringTag]() {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return (this.constructor as any).lc_name();
+  }
+
+  // Override the default behavior of console.log
+  [Symbol.for("nodejs.util.inspect.custom")](depth: number | null) {
+    if (depth === null) {
+      return this;
+    }
+    const printable = stringifyWithDepthLimit(
+      this._printableFields,
+      Math.max(4, depth)
+    );
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return `${(this.constructor as any).lc_name()} ${printable}`;
+  }
 }
 
 // TODO: Deprecate when SDK typing is updated

langchain-core/src/messages/chat.ts

@@ -48,6 +48,13 @@ export class ChatMessage
   static isInstance(message: BaseMessage): message is ChatMessage {
     return message._getType() === "generic";
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      role: this.role,
+    };
+  }
 }
 
 /**
@@ -93,4 +100,11 @@ export class ChatMessageChunk extends BaseMessageChunk {
       id: this.id ?? chunk.id,
     });
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      role: this.role,
+    };
+  }
 }

langchain-core/src/messages/modifier.ts

@@ -28,4 +28,11 @@ export class RemoveMessage extends BaseMessage {
   _getType(): MessageType {
     return "remove";
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      id: this.id,
+    };
+  }
 }

langchain-core/src/messages/tool.ts

@@ -75,6 +75,14 @@ export class ToolMessage extends BaseMessage {
   static isInstance(message: BaseMessage): message is ToolMessage {
     return message._getType() === "tool";
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      tool_call_id: this.tool_call_id,
+      artifact: this.artifact,
+    };
+  }
 }
 
 /**
@@ -124,6 +132,14 @@ export class ToolMessageChunk extends BaseMessageChunk {
       id: this.id ?? chunk.id,
     });
   }
+
+  override get _printableFields(): Record<string, unknown> {
+    return {
+      ...super._printableFields,
+      tool_call_id: this.tool_call_id,
+      artifact: this.artifact,
+    };
+  }
 }
 
 /**