langgraph: add stateful entrypoint

libs/langgraph/langgraph/func/__init__.py

@@ -1,4 +1,4 @@
 import asyncio
 import concurrent
 import concurrent.futures
 import functools
@@ -9,8 +9,10 @@
     Awaitable,
     Callable,
     Optional,
+    Type,
     TypeVar,
     Union,
+    get_type_hints,
     overload,
 )
 
@@ -20,6 +22,7 @@
 from langgraph.channels.last_value import LastValue
 from langgraph.checkpoint.base import BaseCheckpointSaver
 from langgraph.constants import END, START, TAG_HIDDEN
+from langgraph.graph.state import StateGraph
 from langgraph.pregel import Pregel
 from langgraph.pregel.call import get_runnable_for_func
 from langgraph.pregel.read import PregelNode
@@ -47,6 +50,14 @@
     return fut
 
 
+def get_store() -> BaseStore:
+    """Get the current store."""
+    from langgraph.constants import CONFIG_KEY_STORE
+    from langgraph.utils.config import get_configurable
+
+    return get_configurable()[CONFIG_KEY_STORE]
+
+
 @overload
 def task(
     *, retry: Optional[RetryPolicy] = None
@@ -153,3 +164,41 @@
         )
 
     return _imp
+
+
+def g(
+    *,
+    checkpointer: Optional[BaseCheckpointSaver] = None,
+    store: Optional[BaseStore] = None,
+    input: Optional[Type[Any]] = None,
+    output: Optional[Type[Any]] = None,
+) -> Callable[[types.FunctionType], Pregel]:
+    """Generate a single node StateGraph from a callable.
+
+    Args:
+        checkpointer: Checkpointer to use for the graph.
+        store: Store to use for the graph.
+        input: Schema projection applied to run input to the graph.
+        output: Schema projection applied to run output from the graph.
+
+    Returns:
+        Callable: A decorator that can be applied to a function to generate a Pregel graph.
+    """
+
+    def decorator(func: Callable) -> Pregel:
+        """Decorator to generate a Pregel graph from a callable."""
+        node_name = func.__name__
+        type_hints = get_type_hints(func)
+        if not type_hints:
+            state_schema = dict
+        else:
+            state_schema = list(type_hints.values())[0]
+        builder = (
+            StateGraph(state_schema=state_schema, input=input, output=output)
+            .add_node(func)
+            .set_entry_point(node_name)
+        )
+        graph = builder.compile(checkpointer=checkpointer, store=store)
+        return graph
+
+    return decorator