docs[patch]: Use an example file for docs code examples (#3567)

* docs[patch]: Use an example file for docs code examples

* cr

* cr

* cr

docs/core_docs/docs/expression_language/how_to/with_history.mdx

@@ -1,5 +1,11 @@
+---
+sidebar_class_name: hidden
+hide_table_of_contents: true
+---
+
 import CodeBlock from "@theme/CodeBlock";
 import Example from "@examples/guides/expression_language/runnable_history.ts";
+import ExampleConstructorConfig from "@examples/guides/expression_language/runnable_history_constructor_config.ts";
 
 # Add message history (memory)
 
@@ -29,25 +35,4 @@ To do this, the only change you need to make is remove the second arg (or just t
 
 This is a simple example building on top of what we have above:
 
-```typescript
-const config: RunnableConfig = { configurable: { sessionId: "1" } };
-
-const withHistory = new RunnableWithMessageHistory({
-  runnable,
-  getMessageHistory: (_sessionId: string) => messageHistory,
-  inputMessagesKey: "input",
-  historyMessagesKey: "history",
-  // Passing config through here instead of through the invoke method
-  config,
-});
-
-let output = await withHistory.invoke({ input: "Hello there, I'm Archibald!" });
-console.log("output 1:", output);
-/**
-output 1: AIMessage {
-  lc_namespace: [ 'langchain_core', 'messages' ],
-  content: 'Hello, Archibald! How can I assist you today?',
-  additional_kwargs: { function_call: undefined, tool_calls: undefined }
-}
- */
-```
+<CodeBlock language="typescript">{ExampleConstructorConfig}</CodeBlock>

examples/src/guides/expression_language/runnable_history_constructor_config.ts

@@ -0,0 +1,45 @@
+import { ChatOpenAI } from "langchain/chat_models/openai";
+import { ChatMessageHistory } from "langchain/stores/message/in_memory";
+import { ChatPromptTemplate, MessagesPlaceholder } from "langchain/prompts";
+import {
+  RunnableConfig,
+  RunnableWithMessageHistory,
+} from "langchain/runnables";
+
+// Construct your runnable with a prompt and chat model.
+const model = new ChatOpenAI({});
+const prompt = ChatPromptTemplate.fromMessages([
+  ["ai", "You are a helpful assistant"],
+  new MessagesPlaceholder("history"),
+  ["human", "{input}"],
+]);
+const runnable = prompt.pipe(model);
+const messageHistory = new ChatMessageHistory();
+
+// Define a RunnableConfig object, with a `configurable` key.
+const config: RunnableConfig = { configurable: { sessionId: "1" } };
+const withHistory = new RunnableWithMessageHistory({
+  runnable,
+  getMessageHistory: (_sessionId: string) => messageHistory,
+  inputMessagesKey: "input",
+  historyMessagesKey: "history",
+  // Passing config through here instead of through the invoke method
+  config,
+});
+
+const output = await withHistory.invoke({
+  input: "Hello there, I'm Archibald!",
+});
+console.log("output:", output);
+/**
+output: AIMessage {
+  lc_namespace: [ 'langchain_core', 'messages' ],
+  content: 'Hello, Archibald! How can I assist you today?',
+  additional_kwargs: { function_call: undefined, tool_calls: undefined }
+}
+ */
+
+/**
+ * You can see the LangSmith traces here:
+ * output @link https://smith.langchain.com/public/ee264a77-b767-4b5a-8573-efcbebaa5c80/r
+ */