@langchain/core/dist/singletons/async_local_storage/context.cjs

Core LangChain.js abstractions and schemas

const require_rolldown_runtime = require('../../_virtual/rolldown_runtime.cjs');
const require_globals = require('./globals.cjs');
const langsmith_run_trees = require_rolldown_runtime.__toESM(require("langsmith/run_trees"));

//#region src/singletons/async_local_storage/context.ts
/**
* Set a context variable. Context variables are scoped to any
* child runnables called by the current runnable, or globally if set outside
* of any runnable.
*
* @remarks
* This function is only supported in environments that support AsyncLocalStorage,
* including Node.js, Deno, and Cloudflare Workers.
*
* @example
* ```ts
* import { RunnableLambda } from "@langchain/core/runnables";
* import {
*   getContextVariable,
*   setContextVariable
* } from "@langchain/core/context";
*
* const nested = RunnableLambda.from(() => {
*   // "bar" because it was set by a parent
*   console.log(getContextVariable("foo"));
*
*   // Override to "baz", but only for child runnables
*   setContextVariable("foo", "baz");
*
*   // Now "baz", but only for child runnables
*   return getContextVariable("foo");
* });
*
* const runnable = RunnableLambda.from(async () => {
*   // Set a context variable named "foo"
*   setContextVariable("foo", "bar");
*
*   const res = await nested.invoke({});
*
*   // Still "bar" since child changes do not affect parents
*   console.log(getContextVariable("foo"));
*
*   return res;
* });
*
* // undefined, because context variable has not been set yet
* console.log(getContextVariable("foo"));
*
* // Final return value is "baz"
* const result = await runnable.invoke({});
* ```
*
* @param name The name of the context variable.
* @param value The value to set.
*/
function setContextVariable(name, value) {
	const asyncLocalStorageInstance = require_globals.getGlobalAsyncLocalStorageInstance();
	if (asyncLocalStorageInstance === void 0) throw new Error(`Internal error: Global shared async local storage instance has not been initialized.`);
	const runTree = asyncLocalStorageInstance.getStore();
	const contextVars = { ...runTree?.[require_globals._CONTEXT_VARIABLES_KEY] };
	contextVars[name] = value;
	let newValue = {};
	if ((0, langsmith_run_trees.isRunTree)(runTree)) newValue = new langsmith_run_trees.RunTree(runTree);
	newValue[require_globals._CONTEXT_VARIABLES_KEY] = contextVars;
	asyncLocalStorageInstance.enterWith(newValue);
}
/**
* Get the value of a previously set context variable. Context variables
* are scoped to any child runnables called by the current runnable,
* or globally if set outside of any runnable.
*
* @remarks
* This function is only supported in environments that support AsyncLocalStorage,
* including Node.js, Deno, and Cloudflare Workers.
*
* @example
* ```ts
* import { RunnableLambda } from "@langchain/core/runnables";
* import {
*   getContextVariable,
*   setContextVariable
* } from "@langchain/core/context";
*
* const nested = RunnableLambda.from(() => {
*   // "bar" because it was set by a parent
*   console.log(getContextVariable("foo"));
*
*   // Override to "baz", but only for child runnables
*   setContextVariable("foo", "baz");
*
*   // Now "baz", but only for child runnables
*   return getContextVariable("foo");
* });
*
* const runnable = RunnableLambda.from(async () => {
*   // Set a context variable named "foo"
*   setContextVariable("foo", "bar");
*
*   const res = await nested.invoke({});
*
*   // Still "bar" since child changes do not affect parents
*   console.log(getContextVariable("foo"));
*
*   return res;
* });
*
* // undefined, because context variable has not been set yet
* console.log(getContextVariable("foo"));
*
* // Final return value is "baz"
* const result = await runnable.invoke({});
* ```
*
* @param name The name of the context variable.
*/
function getContextVariable(name) {
	const asyncLocalStorageInstance = require_globals.getGlobalAsyncLocalStorageInstance();
	if (asyncLocalStorageInstance === void 0) return void 0;
	const runTree = asyncLocalStorageInstance.getStore();
	return runTree?.[require_globals._CONTEXT_VARIABLES_KEY]?.[name];
}
const LC_CONFIGURE_HOOKS_KEY = Symbol("lc:configure_hooks");
const _getConfigureHooks = () => getContextVariable(LC_CONFIGURE_HOOKS_KEY) || [];
/**
* Register a callback configure hook to automatically add callback handlers to all runs.
*
* There are two ways to use this:
*
* 1. Using a context variable:
*    - Set `contextVar` to specify the variable name
*    - Use `setContextVariable()` to store your handler instance
*
* 2. Using an environment variable:
*    - Set both `envVar` and `handlerClass`
*    - The handler will be instantiated when the env var is set to "true".
*
* @example
* ```typescript
* // Method 1: Using context variable
* import {
*   registerConfigureHook,
*   setContextVariable
* } from "@langchain/core/context";
*
* const tracer = new MyCallbackHandler();
* registerConfigureHook({
*   contextVar: "my_tracer",
* });
* setContextVariable("my_tracer", tracer);
*
* // ...run code here
*
* // Method 2: Using environment variable
* registerConfigureHook({
*   handlerClass: MyCallbackHandler,
*   envVar: "MY_TRACER_ENABLED",
* });
* process.env.MY_TRACER_ENABLED = "true";
*
* // ...run code here
* ```
*
* @param config Configuration object for the hook
* @param config.contextVar Name of the context variable containing the handler instance
* @param config.inheritable Whether child runs should inherit this handler
* @param config.handlerClass Optional callback handler class (required if using envVar)
* @param config.envVar Optional environment variable name to control handler activation
*/
const registerConfigureHook = (config) => {
	if (config.envVar && !config.handlerClass) throw new Error("If envVar is set, handlerClass must also be set to a non-None value.");
	setContextVariable(LC_CONFIGURE_HOOKS_KEY, [..._getConfigureHooks(), config]);
};

//#endregion
exports._getConfigureHooks = _getConfigureHooks;
exports.getContextVariable = getContextVariable;
exports.registerConfigureHook = registerConfigureHook;
exports.setContextVariable = setContextVariable;
//# sourceMappingURL=context.cjs.map