@langchain/langgraph/dist/pregel/stream.cjs.map

LangGraph

{"version":3,"file":"stream.cjs","names":["IterableReadableStream","BaseCallbackHandler","isCheckpointEnvelope"],"sources":["../../src/pregel/stream.ts"],"sourcesContent":["import { IterableReadableStream } from \"@langchain/core/utils/stream\";\nimport type { RunnableConfig } from \"@langchain/core/runnables\";\nimport { BaseCallbackHandler } from \"@langchain/core/callbacks/base\";\nimport { Serialized } from \"@langchain/core/load/serializable\";\nimport { isCheckpointEnvelope } from \"../stream/convert.js\";\nimport type { Checkpoint } from \"../stream/types.js\";\nimport type { StreamMode, StreamOutputMap } from \"./types.js\";\nimport { TAG_HIDDEN } from \"../constants.js\";\n\n/**\n * Optional chunk-level metadata carried alongside the payload. Used by\n * `streamEvents(..., { version: \"v3\" })` to emit a companion `checkpoints`\n * protocol event adjacent to the `values` event for the same superstep, so\n * clients can build branching / time-travel UIs without subscribing to a\n * full-state `checkpoints` stream.\n *\n * Companion checkpoint envelopes are emitted as separate\n * ``[namespace, \"checkpoints\", envelope]`` chunks (see\n * ``PregelLoop._emitValuesWithCheckpointMeta``).\n */\nexport interface StreamChunkMeta {\n  /**\n   * Lightweight checkpoint envelope for the superstep that produced the\n   * paired `values` chunk. Shape matches the canonical {@link Checkpoint}\n   * generated from `protocol.cddl`.\n   */\n  checkpoint?: Checkpoint;\n}\n\n// [namespace, streamMode, payload]\nexport type StreamChunk = [string[], StreamMode, unknown];\n\ntype StreamCheckpointsOutput<StreamValues> = StreamOutputMap<\n  \"checkpoints\",\n  false,\n  StreamValues,\n  unknown,\n  string,\n  unknown,\n  unknown,\n  undefined\n>;\n\ntype AnyStreamOutput = StreamOutputMap<\n  StreamMode[],\n  true,\n  unknown,\n  unknown,\n  string,\n  unknown,\n  unknown,\n  undefined\n>;\n\ntype ToolRunInfo = {\n  ns: string[];\n  toolCallId?: string;\n  toolName: string;\n  input: unknown;\n};\n\n/**\n * A wrapper around an IterableReadableStream that allows for aborting the stream when\n * {@link cancel} is called.\n */\nexport class IterableReadableStreamWithAbortSignal<\n  T,\n> extends IterableReadableStream<T> {\n  protected _abortController: AbortController;\n\n  protected _innerReader: ReadableStreamDefaultReader<T>;\n\n  /**\n   * @param readableStream - The stream to wrap.\n   * @param abortController - The abort controller to use. Optional. One will be created if not provided.\n   */\n  constructor(\n    readableStream: ReadableStream<T>,\n    abortController?: AbortController\n  ) {\n    const reader = readableStream.getReader();\n    const ac = abortController ?? new AbortController();\n    super({\n      start(controller: ReadableStreamDefaultController<T>) {\n        return pump();\n        function pump(): Promise<T | undefined> {\n          return reader.read().then(({ done, value }) => {\n            // When no more data needs to be consumed, close the stream\n            if (done) {\n              controller.close();\n              return;\n            }\n            // Enqueue the next data chunk into our target stream\n            controller.enqueue(value);\n            return pump();\n          });\n        }\n      },\n    });\n    this._abortController = ac;\n    this._innerReader = reader;\n  }\n\n  /**\n   * Aborts the stream, abandoning any pending operations in progress. Calling this triggers an\n   * {@link AbortSignal} that is propagated to the tasks that are producing the data for this stream.\n   * @param reason - The reason for aborting the stream. Optional.\n   */\n  override async cancel(reason?: unknown) {\n    this._abortController.abort(reason);\n    this._innerReader.releaseLock();\n  }\n\n  /**\n   * The {@link AbortSignal} for the stream. Aborted when {@link cancel} is called.\n   */\n  get signal() {\n    return this._abortController.signal;\n  }\n}\n\nexport class IterableReadableWritableStream extends IterableReadableStream<StreamChunk> {\n  modes: Set<StreamMode>;\n\n  private controller: ReadableStreamDefaultController;\n\n  private passthroughFn?: (chunk: StreamChunk) => void;\n\n  private _closed: boolean = false;\n\n  get closed() {\n    return this._closed;\n  }\n\n  constructor(params: {\n    passthroughFn?: (chunk: StreamChunk) => void;\n    modes: Set<StreamMode>;\n  }) {\n    let streamControllerPromiseResolver: (\n      controller: ReadableStreamDefaultController\n    ) => void;\n    const streamControllerPromise: Promise<ReadableStreamDefaultController> =\n      new Promise<ReadableStreamDefaultController>((resolve) => {\n        streamControllerPromiseResolver = resolve;\n      });\n\n    super({\n      start: (controller) => {\n        streamControllerPromiseResolver!(controller);\n      },\n    });\n\n    // .start() will always be called before the stream can be interacted\n    // with anyway\n    void streamControllerPromise.then((controller) => {\n      this.controller = controller;\n    });\n\n    this.passthroughFn = params.passthroughFn;\n    this.modes = params.modes;\n  }\n\n  push(chunk: StreamChunk) {\n    // Prevent pushing to a closed stream to avoid race condition errors\n    if (this._closed || !this.controller) {\n      // Silently drop chunks when stream is closed - this is expected behavior\n      // when async operations try to push after stream termination\n      return;\n    }\n\n    // Forward chunk to passthrough function if provided\n    this.passthroughFn?.(chunk);\n\n    // Attempt to enqueue the chunk to the underlying stream\n    this.controller.enqueue(chunk);\n  }\n\n  close() {\n    try {\n      this.controller.close();\n    } catch {\n      // pass\n    } finally {\n      this._closed = true;\n    }\n  }\n\n  // eslint-disable-next-line @typescript-eslint/no-explicit-any\n  error(e: any) {\n    try {\n      this.controller?.error(e);\n    } finally {\n      // Mark the stream as closed so any late `push()` calls from in-flight\n      // parallel tasks are dropped instead of throwing on an errored controller.\n      this._closed = true;\n    }\n  }\n}\n\n/**\n * A callback handler that implements stream_mode=tools.\n * Emits on_tool_start, on_tool_event, on_tool_end, on_tool_error events.\n */\nexport class StreamToolsHandler extends BaseCallbackHandler {\n  name = \"StreamToolsHandler\";\n\n  /** Ensure tool lifecycle callbacks run before tool.invoke returns/errors. */\n  awaitHandlers = true;\n\n  streamFn: (streamChunk: StreamChunk) => void;\n\n  runs: Record<string, ToolRunInfo | undefined> = {};\n\n  constructor(streamFn: (streamChunk: StreamChunk) => void) {\n    super();\n    this.streamFn = streamFn;\n  }\n\n  handleToolStart(\n    _tool: Serialized,\n    input: string,\n    runId: string,\n    _parentRunId?: string,\n    tags?: string[],\n    metadata?: Record<string, unknown>,\n    runName?: string,\n    toolCallId?: string\n  ) {\n    if (!metadata || (tags && tags.includes(TAG_HIDDEN))) return;\n\n    const ns = (metadata.langgraph_checkpoint_ns as string)?.split(\"|\") ?? [];\n    const info: ToolRunInfo = {\n      ns,\n      toolCallId,\n      toolName: runName ?? \"unknown\",\n      input,\n    };\n    this.runs[runId] = info;\n\n    this.streamFn([\n      ns,\n      \"tools\",\n      {\n        event: \"on_tool_start\",\n        toolCallId: info.toolCallId,\n        name: info.toolName,\n        input,\n      },\n    ]);\n  }\n\n  handleToolEvent(chunk: unknown, runId: string) {\n    const info = this.runs[runId];\n    if (!info) return;\n\n    this.streamFn([\n      info.ns,\n      \"tools\",\n      {\n        event: \"on_tool_event\",\n        toolCallId: info.toolCallId,\n        name: info.toolName,\n        data: chunk,\n      },\n    ]);\n  }\n\n  handleToolEnd(output: unknown, runId: string) {\n    const info = this.runs[runId];\n    delete this.runs[runId];\n    if (!info) return;\n\n    this.streamFn([\n      info.ns,\n      \"tools\",\n      {\n        event: \"on_tool_end\",\n        toolCallId: info.toolCallId,\n        name: info.toolName,\n        output,\n      },\n    ]);\n  }\n\n  handleToolError(err: unknown, runId: string) {\n    const info = this.runs[runId];\n    delete this.runs[runId];\n    if (!info) return;\n\n    this.streamFn([\n      info.ns,\n      \"tools\",\n      {\n        event: \"on_tool_error\",\n        toolCallId: info.toolCallId,\n        name: info.toolName,\n        error: err,\n      },\n    ]);\n  }\n}\n\nfunction _stringifyAsDict(obj: unknown) {\n  return JSON.stringify(obj, function (key: string | number, value: unknown) {\n    const rawValue = this[key];\n    if (\n      rawValue != null &&\n      typeof rawValue === \"object\" &&\n      \"toDict\" in rawValue &&\n      typeof rawValue.toDict === \"function\"\n    ) {\n      const { type, data } = rawValue.toDict();\n      return { ...data, type };\n    }\n\n    return value;\n  });\n}\n\nfunction _serializeError(error: unknown) {\n  // eslint-disable-next-line no-instanceof/no-instanceof\n  if (error instanceof Error) {\n    return { error: error.name, message: error.message };\n  }\n  return { error: \"Error\", message: JSON.stringify(error) };\n}\n\nfunction _isRunnableConfig(\n  config: unknown\n): config is RunnableConfig & { configurable: Record<string, unknown> } {\n  if (typeof config !== \"object\" || config == null) return false;\n  return (\n    \"configurable\" in config &&\n    typeof config.configurable === \"object\" &&\n    config.configurable != null\n  );\n}\n\nfunction _extractCheckpointFromConfig(\n  config: RunnableConfig | null | undefined\n) {\n  if (!_isRunnableConfig(config) || !config.configurable.thread_id) {\n    return null;\n  }\n\n  return {\n    thread_id: config.configurable.thread_id,\n    checkpoint_ns: config.configurable.checkpoint_ns || \"\",\n    checkpoint_id: config.configurable.checkpoint_id || null,\n    checkpoint_map: config.configurable.checkpoint_map || null,\n  };\n}\n\nfunction _serializeConfig(config: unknown) {\n  if (_isRunnableConfig(config)) {\n    const configurable = Object.fromEntries(\n      Object.entries(config.configurable).filter(\n        ([key]) => !key.startsWith(\"__\")\n      )\n    );\n\n    const newConfig = { ...config, configurable };\n    delete newConfig.callbacks;\n    return newConfig;\n  }\n\n  return config;\n}\n\nfunction _serializeCheckpoint(payload: StreamCheckpointsOutput<unknown>) {\n  const result: Record<string, unknown> = {\n    ...payload,\n    checkpoint: _extractCheckpointFromConfig(payload.config),\n    parent_checkpoint: _extractCheckpointFromConfig(payload.parentConfig),\n\n    config: _serializeConfig(payload.config),\n    parent_config: _serializeConfig(payload.parentConfig),\n\n    tasks: payload.tasks.map((task) => {\n      if (_isRunnableConfig(task.state)) {\n        const checkpoint = _extractCheckpointFromConfig(task.state);\n        if (checkpoint != null) {\n          const cloneTask: Record<string, unknown> = { ...task, checkpoint };\n          delete cloneTask.state;\n          return cloneTask;\n        }\n      }\n\n      return task;\n    }),\n  };\n\n  delete result.parentConfig;\n  return result;\n}\n\nexport function toEventStream(stream: AsyncGenerator) {\n  const encoder = new TextEncoder();\n  return new ReadableStream<Uint8Array>({\n    async start(controller) {\n      const enqueueChunk = (sse: {\n        id?: string;\n        event: string;\n        data: unknown;\n      }) => {\n        controller.enqueue(\n          encoder.encode(\n            `event: ${sse.event}\\ndata: ${_stringifyAsDict(sse.data)}\\n\\n`\n          )\n        );\n      };\n\n      try {\n        for await (const payload of stream) {\n          const [ns, mode, chunk] = payload as AnyStreamOutput;\n\n          let data: unknown = chunk;\n          if (mode === \"debug\") {\n            const debugChunk = chunk;\n\n            if (debugChunk.type === \"checkpoint\") {\n              data = {\n                ...debugChunk,\n                payload: _serializeCheckpoint(debugChunk.payload),\n              };\n            }\n          }\n\n          if (mode === \"checkpoints\") {\n            data = _serializeCheckpoint(chunk);\n          }\n\n          const event = ns?.length ? `${mode}|${ns.join(\"|\")}` : mode;\n          enqueueChunk({ event, data });\n        }\n      } catch (error) {\n        enqueueChunk({ event: \"error\", data: _serializeError(error) });\n      }\n\n      controller.close();\n    },\n  });\n}\n\n/** Multiplex subgraph stream chunks into the parent pregel stream. */\nexport function createDuplexStream(\n  ...streams: IterableReadableWritableStream[]\n) {\n  return new IterableReadableWritableStream({\n    passthroughFn: (value: StreamChunk) => {\n      const isEnvelope =\n        value[1] === \"checkpoints\" && isCheckpointEnvelope(value[2]);\n      for (const stream of streams) {\n        if (stream.modes.has(value[1]) || isEnvelope) {\n          stream.push(value);\n        }\n      }\n    },\n    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