tidy up constants

langchain-ai · Jan 28, 2025 · eaf1c85 · eaf1c85
1 parent d100e7e
commit eaf1c85
Show file tree

Hide file tree

Showing 4 changed files with 22 additions and 26 deletions.
diff --git a/libs/langgraph/src/constants.ts b/libs/langgraph/src/constants.ts
@@ -5,25 +5,31 @@ export const END = "__end__";
 export const INPUT = "__input__";
 export const ERROR = "__error__";
 export const CONFIG_KEY_SEND = "__pregel_send";
+/** config key containing function used to call a node (push task) */
 export const CONFIG_KEY_CALL = "__pregel_call";
 export const CONFIG_KEY_READ = "__pregel_read";
 export const CONFIG_KEY_CHECKPOINTER = "__pregel_checkpointer";
 export const CONFIG_KEY_RESUMING = "__pregel_resuming";
 export const CONFIG_KEY_TASK_ID = "__pregel_task_id";
 export const CONFIG_KEY_STREAM = "__pregel_stream";
-export const CONFIG_KEY_GENERATOR_WRITER = "__pregel_generator_writer";
 export const CONFIG_KEY_RESUME_VALUE = "__pregel_resume_value";
 export const CONFIG_KEY_SCRATCHPAD = "__pregel_scratchpad";
-export const CONFIG_KEY_PREVIOUS = "__pregel_previous";
+/** config key containing state from previous invocation of graph for the given thread */
+export const CONFIG_KEY_PREVIOUS_STATE = "__pregel_previous";
 export const CONFIG_KEY_CHECKPOINT_NS = "checkpoint_ns";
 
 // this one is part of public API
 export const CONFIG_KEY_CHECKPOINT_MAP = "checkpoint_map";
 
+/** Special channel reserved for graph interrupts */
 export const INTERRUPT = "__interrupt__";
+/** Special channel reserved for graph resume */
 export const RESUME = "__resume__";
+/** Special channel reserved for cases when a task exits without any writes */
 export const NO_WRITES = "__no_writes__";
+/** Special channel reserved for graph return */
 export const RETURN = "__return__";
+/** Special channel reserved for graph previous state */
 export const PREVIOUS = "__previous__";
 export const RUNTIME_PLACEHOLDER = "__pregel_runtime_placeholder__";
 export const RECURSION_LIMIT_DEFAULT = 25;

diff --git a/libs/langgraph/src/func/index.ts b/libs/langgraph/src/func/index.ts
@@ -5,7 +5,12 @@ import {
 import { AsyncLocalStorageProviderSingleton } from "@langchain/core/singletons";
 import { Pregel } from "../pregel/index.js";
 import { PregelNode } from "../pregel/read.js";
-import { CONFIG_KEY_PREVIOUS, END, PREVIOUS, START } from "../constants.js";
+import {
+  CONFIG_KEY_PREVIOUS_STATE,
+  END,
+  PREVIOUS,
+  START,
+} from "../constants.js";
 import { EphemeralValue } from "../channels/ephemeral_value.js";
 import { call, getRunnableForEntrypoint } from "../pregel/call.js";
 import { RetryPolicy } from "../pregel/utils/index.js";
@@ -173,5 +178,5 @@ entrypoint.final = function final<ValueT, SaveT>({
 export function getPreviousState<StateT>(): StateT {
   const config: LangGraphRunnableConfig =
     AsyncLocalStorageProviderSingleton.getRunnableConfig();
-  return config.configurable?.[CONFIG_KEY_PREVIOUS] as StateT;
+  return config.configurable?.[CONFIG_KEY_PREVIOUS_STATE] as StateT;
 }
diff --git a/libs/langgraph/src/pregel/algo.ts b/libs/langgraph/src/pregel/algo.ts
@@ -49,9 +49,8 @@ import {
   RETURN,
   ERROR,
   NO_WRITES,
-  CONFIG_KEY_PREVIOUS,
+  CONFIG_KEY_PREVIOUS_STATE,
   PREVIOUS,
-  CONFIG_KEY_GENERATOR_WRITER,
 } from "../constants.js";
 import {
   Call,
@@ -644,14 +643,9 @@ export function _prepareSingleTask<
                 ],
                 id
               ),
-              [CONFIG_KEY_PREVIOUS]: checkpoint.channel_values[PREVIOUS],
+              [CONFIG_KEY_PREVIOUS_STATE]: checkpoint.channel_values[PREVIOUS],
               checkpoint_id: undefined,
               checkpoint_ns: taskCheckpointNamespace,
-              // Used by the functional API iff the entrypoint is a generator function. It's necessary to set it regardless
-              // of streammode, because we can't tell when initializing the graph whether the entrypoint is a function that
-              // returns a generator.
-              [CONFIG_KEY_GENERATOR_WRITER]: (chunk: unknown) =>
-                extra.stream?.push([[], "custom", chunk]),
             },
           }
         ),
@@ -786,14 +780,10 @@ export function _prepareSingleTask<
                   ],
                   taskId
                 ),
-                [CONFIG_KEY_PREVIOUS]: checkpoint.channel_values[PREVIOUS],
+                [CONFIG_KEY_PREVIOUS_STATE]:
+                  checkpoint.channel_values[PREVIOUS],
                 checkpoint_id: undefined,
                 checkpoint_ns: taskCheckpointNamespace,
-                // Used by the functional API iff the entrypoint is a generator function. It's necessary to set it regardless
-                // of streammode, because we can't tell when initializing the graph whether the entrypoint is a function that
-                // returns a generator.
-                [CONFIG_KEY_GENERATOR_WRITER]: (chunk: unknown) =>
-                  extra.stream?.push([[], "custom", chunk]),
               },
             }
           ),
@@ -940,14 +930,10 @@ export function _prepareSingleTask<
                     ],
                     taskId
                   ),
-                  [CONFIG_KEY_PREVIOUS]: checkpoint.channel_values[PREVIOUS],
+                  [CONFIG_KEY_PREVIOUS_STATE]:
+                    checkpoint.channel_values[PREVIOUS],
                   checkpoint_id: undefined,
                   checkpoint_ns: taskCheckpointNamespace,
-                  // Used by the functional API iff the entrypoint is a generator function. It's necessary to set it regardless
-                  // of streammode, because we can't tell when initializing the graph whether the entrypoint is a function that
-                  // returns a generator.
-                  [CONFIG_KEY_GENERATOR_WRITER]: (chunk: unknown) =>
-                    extra.stream?.push([[], "custom", chunk]),
                 },
               }
             ),

diff --git a/libs/langgraph/src/pregel/utils/config.ts b/libs/langgraph/src/pregel/utils/config.ts
@@ -2,7 +2,6 @@ import { RunnableConfig } from "@langchain/core/runnables";
 import { AsyncLocalStorageProviderSingleton } from "@langchain/core/singletons";
 import { BaseStore } from "@langchain/langgraph-checkpoint";
 import { LangGraphRunnableConfig } from "../runnable_types.js";
-import { CONFIG_KEY_GENERATOR_WRITER } from "../../constants.js";
 
 const COPIABLE_KEYS = ["tags", "metadata", "callbacks", "configurable"];
 
@@ -114,7 +113,7 @@ export function getStore(): BaseStore | undefined {
 export function getWriter(): ((chunk: unknown) => void) | undefined {
   const config: LangGraphRunnableConfig =
     AsyncLocalStorageProviderSingleton.getRunnableConfig();
-  return config?.configurable?.[CONFIG_KEY_GENERATOR_WRITER];
+  return config?.configurable?.writer;
 }
 
 export function getConfig(): LangGraphRunnableConfig {