langchain-ai/langgraph
1
0
Fork 0
mirror of https://github.com/langchain-ai/langgraph.git synced 2026-07-15 12:35:43 -04:00
Code Issues 314 Packages Projects Releases 17 Wiki Activity

[PR #6543] Fix type signature for add_conditional_edges path_map parameter #5111

New Issue
Closed
opened 2026-02-20 17:51:14 -05:00 by yindo · 0 comments
yindo commented 2026-02-20 17:51:14 -05:00
Owner
Copy Link
Copy Source

Original Pull Request: https://github.com/langchain-ai/langgraph/pull/6543

State: closed
Merged: No

Summary

Fixes the type signature incompatibility in add_conditional_edges where dict[str, str] could not be assigned to dict[Hashable, str] due to Python's type invariance.

Problem

The current type signature uses dict[Hashable, str] for the path_map parameter:

def add_conditional_edges(
    self,
    source: str,
    path: Callable[..., Hashable | Sequence[Hashable]],
    path_map: dict[Hashable, str] | list[str] | None = None,
) -> Self:

This causes pyright/mypy errors when passing a dict[str, str]:

path_map: dict[str, str] = {"yes": "approved", "no": "rejected"}
graph.add_conditional_edges("__start__", check_approval, path_map)
# Error: dict[str, str] is not assignable to dict[Hashable, str]

Solution

Introduced a TypeVar bound to Hashable that links the return type of path with the key type of path_map:

_PathReturnT = TypeVar("_PathReturnT", bound=Hashable)

def add_conditional_edges(
    self,
    source: str,
    path: Callable[..., _PathReturnT | Sequence[_PathReturnT]]
        | Callable[..., Awaitable[_PathReturnT | Sequence[_PathReturnT]]]
        | Runnable[Any, _PathReturnT | Sequence[_PathReturnT]],
    path_map: dict[_PathReturnT, str] | list[str] | None = None,
) -> Self:

This allows:

  • dict[str, str] when path returns str
  • dict[MyEnum, str] when path returns MyEnum
  • Type safety is preserved since _PathReturnT is bound to Hashable

Testing

Verified the fix works with the example from the issue:

from typing import TypedDict
from langgraph.graph import END, StateGraph

class State(TypedDict):
    approved: bool

def check_approval(state: State) -> str:
    return "yes" if state["approved"] else "no"

graph = StateGraph(State)
graph.add_node("approved", approved_node)
graph.add_node("rejected", rejected_node)

# This now works without type errors!
path_map: dict[str, str] = {"yes": "approved", "no": "rejected"}
graph.add_conditional_edges("__start__", check_approval, path_map)

Closes #6540

**Original Pull Request:** https://github.com/langchain-ai/langgraph/pull/6543 **State:** closed **Merged:** No --- ## Summary Fixes the type signature incompatibility in `add_conditional_edges` where `dict[str, str]` could not be assigned to `dict[Hashable, str]` due to Python's type invariance. ## Problem The current type signature uses `dict[Hashable, str]` for the `path_map` parameter: ```python def add_conditional_edges( self, source: str, path: Callable[..., Hashable | Sequence[Hashable]], path_map: dict[Hashable, str] | list[str] | None = None, ) -> Self: ``` This causes pyright/mypy errors when passing a `dict[str, str]`: ```python path_map: dict[str, str] = {"yes": "approved", "no": "rejected"} graph.add_conditional_edges("__start__", check_approval, path_map) # Error: dict[str, str] is not assignable to dict[Hashable, str] ``` ## Solution Introduced a `TypeVar` bound to `Hashable` that links the return type of `path` with the key type of `path_map`: ```python _PathReturnT = TypeVar("_PathReturnT", bound=Hashable) def add_conditional_edges( self, source: str, path: Callable[..., _PathReturnT | Sequence[_PathReturnT]] | Callable[..., Awaitable[_PathReturnT | Sequence[_PathReturnT]]] | Runnable[Any, _PathReturnT | Sequence[_PathReturnT]], path_map: dict[_PathReturnT, str] | list[str] | None = None, ) -> Self: ``` This allows: - `dict[str, str]` when `path` returns `str` - `dict[MyEnum, str]` when `path` returns `MyEnum` - Type safety is preserved since `_PathReturnT` is bound to `Hashable` ## Testing Verified the fix works with the example from the issue: ```python from typing import TypedDict from langgraph.graph import END, StateGraph class State(TypedDict): approved: bool def check_approval(state: State) -> str: return "yes" if state["approved"] else "no" graph = StateGraph(State) graph.add_node("approved", approved_node) graph.add_node("rejected", rejected_node) # This now works without type errors! path_map: dict[str, str] = {"yes": "approved", "no": "rejected"} graph.add_conditional_edges("__start__", check_approval, path_map) ``` Closes #6540
yindo added the pull-request label 2026-02-20 17:51:14 -05:00
yindo closed this issue 2026-02-20 17:51:14 -05:00
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
agents
awaiting author revision
bug
change
chat models
checkpointer
ci
code quality
code quality
dependencies
documentation
drawing
duplicate
enhancement
good first issue
help wanted
invalid
maintainer
meta
missing information
not maintained by langchain
open-swe-auto
open-swe-max
open-swe-max-auto
pending
performance
pull-request
Mirrored from GitHub Pull Request
 question
requires design
sdk
server
stale
studio
tests
type checking
usage question
v0.5
v1.1
No Label pull-request
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
yindo
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: langchain-ai/langgraph#5111
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?