@langchain/langgraph/dist/channels/untracked_value.js

LangGraph

import { EmptyChannelError, InvalidUpdateError } from "../errors.js";
import { BaseChannel } from "./base.js";
//#region src/channels/untracked_value.ts
const MISSING = Symbol.for("langgraph.channel.missing");
/**
* Stores the last value received, never checkpointed.
*
* This channel stores values during graph execution but does NOT persist
* the value to checkpoints. On restoration from a checkpoint, the value
* will be reset to empty (or the initial value if provided).
*
* Useful for transient state like:
* - Database connections
* - Temporary caches
* - Runtime-only configuration
*
* @internal
*/
var UntrackedValueChannel = class UntrackedValueChannel extends BaseChannel {
	lc_graph_name = "UntrackedValue";
	/**
	* If true, throws an error when multiple values are received in a single step.
	* If false, stores the last value received.
	*/
	guard;
	/**
	* The current value. MISSING sentinel indicates no value has been set.
	*/
	_value = MISSING;
	/**
	* Optional factory function for the initial value.
	*/
	initialValueFactory;
	constructor(options) {
		super();
		this.guard = options?.guard ?? true;
		this.initialValueFactory = options?.initialValueFactory;
		if (this.initialValueFactory) this._value = this.initialValueFactory();
	}
	/**
	* Return a new channel, ignoring the checkpoint since we don't persist.
	* The initial value (if any) is restored.
	*/
	fromCheckpoint(_checkpoint) {
		return new UntrackedValueChannel({
			guard: this.guard,
			initialValueFactory: this.initialValueFactory
		});
	}
	/**
	* Update the channel with the given values.
	* If guard is true, throws if more than one value is received.
	*/
	update(values) {
		if (values.length === 0) return false;
		if (values.length !== 1 && this.guard) throw new InvalidUpdateError("UntrackedValue(guard=true) can receive only one value per step. Use guard=false if you want to store any one of multiple values.", { lc_error_code: "INVALID_CONCURRENT_GRAPH_UPDATE" });
		this._value = values[values.length - 1];
		return true;
	}
	/**
	* Get the current value.
	* @throws EmptyChannelError if no value has been set.
	*/
	get() {
		if (this._value === MISSING) throw new EmptyChannelError();
		return this._value;
	}
	/**
	* Always returns undefined - untracked values are never checkpointed.
	*/
	checkpoint() {}
	/**
	* Return true if a value has been set.
	*/
	isAvailable() {
		return this._value !== MISSING;
	}
};
//#endregion
export { UntrackedValueChannel };

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