@langchain/langgraph
Version:
LangGraph
124 lines • 3.96 kB
JavaScript
import { BinaryOperatorAggregate } from "../channels/binop.js";
import { LastValue } from "../channels/last_value.js";
import { isConfiguredManagedValue, } from "../managed/base.js";
/**
* Should not be instantiated directly. See {@link Annotation}.
*/
export class AnnotationRoot {
constructor(s) {
Object.defineProperty(this, "lc_graph_name", {
enumerable: true,
configurable: true,
writable: true,
value: "AnnotationRoot"
});
Object.defineProperty(this, "spec", {
enumerable: true,
configurable: true,
writable: true,
value: void 0
});
this.spec = s;
}
}
/**
* Helper that instantiates channels within a StateGraph state.
*
* Can be used as a field in an {@link Annotation.Root} wrapper in one of two ways:
* 1. **Directly**: Creates a channel that stores the most recent value returned from a node.
* 2. **With a reducer**: Creates a channel that applies the reducer on a node's return value.
*
* @example
* ```ts
* import { StateGraph, Annotation } from "@langchain/langgraph";
*
* // Define a state with a single string key named "currentOutput"
* const SimpleAnnotation = Annotation.Root({
* currentOutput: Annotation<string>,
* });
*
* const graphBuilder = new StateGraph(SimpleAnnotation);
*
* // A node in the graph that returns an object with a "currentOutput" key
* // replaces the value in the state. You can get the state type as shown below:
* const myNode = (state: typeof SimpleAnnotation.State) => {
* return {
* currentOutput: "some_new_value",
* };
* }
*
* const graph = graphBuilder
* .addNode("myNode", myNode)
* ...
* .compile();
* ```
*
* @example
* ```ts
* import { type BaseMessage, AIMessage } from "@langchain/core/messages";
* import { StateGraph, Annotation } from "@langchain/langgraph";
*
* // Define a state with a single key named "messages" that will
* // combine a returned BaseMessage or arrays of BaseMessages
* const AnnotationWithReducer = Annotation.Root({
* messages: Annotation<BaseMessage[]>({
* // Different types are allowed for updates
* reducer: (left: BaseMessage[], right: BaseMessage | BaseMessage[]) => {
* if (Array.isArray(right)) {
* return left.concat(right);
* }
* return left.concat([right]);
* },
* default: () => [],
* }),
* });
*
* const graphBuilder = new StateGraph(AnnotationWithReducer);
*
* // A node in the graph that returns an object with a "messages" key
* // will update the state by combining the existing value with the returned one.
* const myNode = (state: typeof AnnotationWithReducer.State) => {
* return {
* messages: [new AIMessage("Some new response")],
* };
* };
*
* const graph = graphBuilder
* .addNode("myNode", myNode)
* ...
* .compile();
* ```
* @namespace
* @property Root
* Helper function that instantiates a StateGraph state. See {@link Annotation} for usage.
*/
export const Annotation = function (annotation) {
if (isConfiguredManagedValue(annotation)) {
return annotation;
}
else if (annotation) {
return getChannel(annotation);
}
else {
// @ts-expect-error - Annotation without reducer
return new LastValue();
}
};
Annotation.Root = (sd) => new AnnotationRoot(sd);
export function getChannel(reducer) {
if (typeof reducer === "object" &&
reducer &&
"reducer" in reducer &&
reducer.reducer) {
return new BinaryOperatorAggregate(reducer.reducer, reducer.default);
}
if (typeof reducer === "object" &&
reducer &&
"value" in reducer &&
reducer.value) {
return new BinaryOperatorAggregate(reducer.value, reducer.default);
}
// @ts-expect-error - Annotation without reducer
return new LastValue();
}
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