feat[core]: message type assertions should accept null | undefined

langchain-core/src/messages/ai.ts

@@ -219,11 +219,15 @@ export class AIMessage extends BaseMessage {
   }
 }
 
-export function isAIMessage(x: BaseMessage): x is AIMessage {
+export function isAIMessage(x: BaseMessage | null | undefined): x is AIMessage {
+  if (!x) return false;
   return x._getType() === "ai";
 }
 
-export function isAIMessageChunk(x: BaseMessageChunk): x is AIMessageChunk {
+export function isAIMessageChunk(
+  x: BaseMessageChunk | null | undefined
+): x is AIMessageChunk {
+  if (!x) return false;
   return x._getType() === "ai";
 }
 

langchain-core/src/messages/base.ts

@@ -544,13 +544,14 @@ export type BaseMessageLike =
   | SerializedConstructor;
 
 export function isBaseMessage(
-  messageLike?: unknown
+  messageLike: unknown | null | undefined
 ): messageLike is BaseMessage {
+  if (!messageLike) return false;
   return typeof (messageLike as BaseMessage)?._getType === "function";
 }
 
 export function isBaseMessageChunk(
-  messageLike?: unknown
+  messageLike: unknown | null | undefined
 ): messageLike is BaseMessageChunk {
   return (
     isBaseMessage(messageLike) &&

langchain-core/src/messages/chat.ts

@@ -45,7 +45,10 @@ export class ChatMessage
     return "generic";
   }
 
-  static isInstance(message: BaseMessage): message is ChatMessage {
+  static isInstance(
+    message: BaseMessage | null | undefined
+  ): message is ChatMessage {
+    if (!message) return false;
     return message._getType() === "generic";
   }
 
@@ -109,10 +112,16 @@ export class ChatMessageChunk extends BaseMessageChunk {
   }
 }
 
-export function isChatMessage(x: BaseMessage): x is ChatMessage {
+export function isChatMessage(
+  x: BaseMessage | null | undefined
+): x is ChatMessage {
+  if (!x) return false;
   return x._getType() === "generic";
 }
 
-export function isChatMessageChunk(x: BaseMessageChunk): x is ChatMessageChunk {
+export function isChatMessageChunk(
+  x: BaseMessageChunk | null | undefined
+): x is ChatMessageChunk {
+  if (!x) return false;
   return x._getType() === "generic";
 }

langchain-core/src/messages/function.ts

@@ -74,12 +74,16 @@ export class FunctionMessageChunk extends BaseMessageChunk {
   }
 }
 
-export function isFunctionMessage(x: BaseMessage): x is FunctionMessage {
+export function isFunctionMessage(
+  x: BaseMessage | null | undefined
+): x is FunctionMessage {
+  if (!x) return false;
   return x._getType() === "function";
 }
 
 export function isFunctionMessageChunk(
-  x: BaseMessageChunk
+  x: BaseMessageChunk | null | undefined
 ): x is FunctionMessageChunk {
+  if (!x) return false;
   return x._getType() === "function";
 }

langchain-core/src/messages/human.ts

@@ -76,12 +76,16 @@ export class HumanMessageChunk extends BaseMessageChunk {
   }
 }
 
-export function isHumanMessage(x: BaseMessage): x is HumanMessage {
+export function isHumanMessage(
+  x: BaseMessage | null | undefined
+): x is HumanMessage {
+  if (!x) return false;
   return x.getType() === "human";
 }
 
 export function isHumanMessageChunk(
-  x: BaseMessageChunk
+  x: BaseMessageChunk | null | undefined
 ): x is HumanMessageChunk {
+  if (!x) return false;
   return x.getType() === "human";
 }

langchain-core/src/messages/system.ts

@@ -75,12 +75,16 @@ export class SystemMessageChunk extends BaseMessageChunk {
   }
 }
 
-export function isSystemMessage(x: BaseMessage): x is SystemMessage {
+export function isSystemMessage(
+  x: BaseMessage | null | undefined
+): x is SystemMessage {
+  if (!x) return false;
   return x._getType() === "system";
 }
 
 export function isSystemMessageChunk(
-  x: BaseMessageChunk
+  x: BaseMessageChunk | null | undefined
 ): x is SystemMessageChunk {
+  if (!x) return false;
   return x._getType() === "system";
 }

langchain-core/src/messages/tool.ts

@@ -115,7 +115,10 @@ export class ToolMessage extends BaseMessage implements DirectToolOutput {
     return "tool";
   }
 
-  static isInstance(message: BaseMessage): message is ToolMessage {
+  static isInstance(
+    message: BaseMessage | null | undefined
+  ): message is ToolMessage {
+    if (!message) return false;
     return message._getType() === "tool";
   }
 
@@ -314,10 +317,16 @@ export function defaultToolCallParser(
   return [toolCalls, invalidToolCalls];
 }
 
-export function isToolMessage(x: BaseMessage): x is ToolMessage {
+export function isToolMessage(
+  x: BaseMessage | null | undefined
+): x is ToolMessage {
+  if (x == null) return false;
   return x._getType() === "tool";
 }
 
-export function isToolMessageChunk(x: BaseMessageChunk): x is ToolMessageChunk {
+export function isToolMessageChunk(
+  x: BaseMessageChunk | null | undefined
+): x is ToolMessageChunk {
+  if (x == null) return false;
   return x._getType() === "tool";
 }