langchain
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Typescript bindings for langchain
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{"version":3,"file":"middleware.cjs","names":["RunnableCallable","fields: RunnableCallableArgs<TStateSchema, NodeOutput<TStateSchema>>","options: MiddlewareNodeOptions","#options","invokeState: TStateSchema","config?: LangGraphRunnableConfig","relevantContext: Record<string, unknown>","state: TStateSchema","runtime: Runtime<TContextSchema>","jumpToConstraint: JumpToTarget[] | undefined","constraint: string | undefined","getHookConstraint","derivePrivateState"],"sources":["../../../src/agents/nodes/middleware.ts"],"sourcesContent":["/* eslint-disable @typescript-eslint/no-explicit-any */\nimport { z } from \"zod/v3\";\nimport { LangGraphRunnableConfig, Command } from \"@langchain/langgraph\";\nimport { interopParse } from \"@langchain/core/utils/types\";\n\nimport { RunnableCallable, RunnableCallableArgs } from \"../RunnableCallable.js\";\nimport type { JumpToTarget } from \"../constants.js\";\nimport type { Runtime } from \"../runtime.js\";\nimport type { AgentMiddleware, MiddlewareResult } from \"../middleware/types.js\";\nimport { derivePrivateState } from \"./utils.js\";\nimport { getHookConstraint } from \"../middleware/utils.js\";\n\n/**\n * Named class for context objects to provide better error messages\n */\nclass AgentContext {}\nclass AgentRuntime {}\n\ntype NodeOutput<TStateSchema extends Record<string, any>> =\n | TStateSchema\n | Command<any, TStateSchema, string>;\n\nexport interface MiddlewareNodeOptions {\n getState: () => Record<string, unknown>;\n}\n\nexport abstract class MiddlewareNode<\n TStateSchema extends Record<string, any>,\n TContextSchema extends Record<string, any>,\n> extends RunnableCallable<TStateSchema, NodeOutput<TStateSchema>> {\n #options: MiddlewareNodeOptions;\n\n abstract middleware: AgentMiddleware<\n z.ZodObject<z.ZodRawShape>,\n z.ZodObject<z.ZodRawShape>\n >;\n\n constructor(\n fields: RunnableCallableArgs<TStateSchema, NodeOutput<TStateSchema>>,\n options: MiddlewareNodeOptions\n ) {\n super(fields);\n this.#options = options;\n }\n\n abstract runHook(\n state: TStateSchema,\n config?: Runtime<TContextSchema>\n ): Promise<MiddlewareResult<TStateSchema>> | MiddlewareResult<TStateSchema>;\n\n async invokeMiddleware(\n invokeState: TStateSchema,\n config?: LangGraphRunnableConfig\n ): Promise<NodeOutput<TStateSchema>> {\n /**\n * Filter context based on middleware's contextSchema\n */\n let filteredContext = {} as TContextSchema;\n /**\n * Parse context using middleware's contextSchema to apply defaults and validation\n */\n if (this.middleware.contextSchema) {\n /**\n * Extract only the fields relevant to this middleware's schema\n */\n const schemaShape = this.middleware.contextSchema?.shape;\n if (schemaShape) {\n const relevantContext: Record<string, unknown> = {};\n const invokeContext = config?.context || {};\n for (const key of Object.keys(schemaShape)) {\n if (key in invokeContext) {\n relevantContext[key] = invokeContext[key];\n }\n }\n /**\n * Parse to apply defaults and validation, even if relevantContext is empty\n * This will throw if required fields are missing and no defaults exist\n */\n filteredContext = interopParse(\n this.middleware.contextSchema,\n relevantContext\n ) as TContextSchema;\n }\n }\n\n const state: TStateSchema = {\n ...this.#options.getState(),\n ...invokeState,\n /**\n * don't overwrite possible outdated messages from other middleware nodes\n */\n messages: invokeState.messages,\n };\n\n /**\n * ToDo: implement later\n */\n const runtime: Runtime<TContextSchema> = {\n context: filteredContext,\n writer: config?.writer,\n interrupt: config?.interrupt,\n signal: config?.signal,\n };\n\n const result = await this.runHook(\n state,\n /**\n * assign runtime and context values into empty named class\n * instances to create a better error message.\n */\n Object.freeze(\n Object.assign(new AgentRuntime(), {\n ...runtime,\n context: Object.freeze(\n Object.assign(new AgentContext(), filteredContext)\n ),\n })\n )\n );\n\n /**\n * If result is undefined, return current state\n */\n if (!result) {\n return { ...state, jumpTo: undefined };\n }\n\n /**\n * Verify that the jump target is allowed for the middleware\n */\n let jumpToConstraint: JumpToTarget[] | undefined;\n let constraint: string | undefined;\n\n if (this.name?.startsWith(\"BeforeAgentNode_\")) {\n jumpToConstraint = getHookConstraint(this.middleware.beforeAgent);\n constraint = \"beforeAgent.canJumpTo\";\n } else if (this.name?.startsWith(\"BeforeModelNode_\")) {\n jumpToConstraint = getHookConstraint(this.middleware.beforeModel);\n constraint = \"beforeModel.canJumpTo\";\n } else if (this.name?.startsWith(\"AfterAgentNode_\")) {\n jumpToConstraint = getHookConstraint(this.middleware.afterAgent);\n constraint = \"afterAgent.canJumpTo\";\n } else if (this.name?.startsWith(\"AfterModelNode_\")) {\n jumpToConstraint = getHookConstraint(this.middleware.afterModel);\n constraint = \"afterModel.canJumpTo\";\n }\n\n if (\n typeof result.jumpTo === \"string\" &&\n !jumpToConstraint?.includes(result.jumpTo as JumpToTarget)\n ) {\n const suggestion =\n jumpToConstraint && jumpToConstraint.length > 0\n ? `must be one of: ${jumpToConstraint?.join(\", \")}.`\n : constraint\n ? `no ${constraint} defined in middleware ${this.middleware.name}`\n : \"\";\n throw new Error(`Invalid jump target: ${result.jumpTo}, ${suggestion}.`);\n }\n\n /**\n * If result is a control action, handle it\n */\n if (typeof result === \"object\" && \"type\" in result) {\n // Handle control actions\n if (result.type === \"terminate\") {\n if (result.error) {\n throw result.error;\n }\n return {\n ...state,\n ...(result.result || {}),\n jumpTo: result.jumpTo,\n };\n }\n\n throw new Error(`Invalid control action: ${JSON.stringify(result)}`);\n }\n\n /**\n * If result is a state update, merge it with current state\n */\n return { ...state, ...result, jumpTo: result.jumpTo };\n }\n\n get nodeOptions(): {\n input: z.ZodObject<TStateSchema>;\n } {\n return {\n input: derivePrivateState(\n this.middleware.stateSchema\n ) as z.ZodObject<TStateSchema>,\n };\n 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