INTPYTHON-619 Confirm invoke behaves as expected when invoked after an interrupt.

libs/langgraph-checkpoint-mongodb/pyproject.toml

@@ -21,6 +21,7 @@ dev = [
     "langchain-core>=0.3.55",
     "langchain-ollama>=0.2.2",
     "langchain-openai>=0.2.14",
+    "langgraph>=0.3.23",
     "langgraph-checkpoint>=2.0.9",
     "pytest-asyncio>=0.21.1",
     "pytest>=7.2.1",

libs/langgraph-checkpoint-mongodb/tests/integration_tests/test_interrupts.py

@@ -0,0 +1,119 @@
+"""Follows https://langchain-ai.github.io/langgraph/how-tos/human_in_the_loop/time-travel"""
+
+import os
+from collections.abc import Generator
+from typing import TypedDict
+
+import pytest
+from langchain_core.runnables import RunnableConfig
+
+from langgraph.checkpoint.base import BaseCheckpointSaver
+from langgraph.checkpoint.memory import InMemorySaver
+from langgraph.checkpoint.mongodb import MongoDBSaver
+from langgraph.graph import END, StateGraph
+from langgraph.graph.graph import CompiledGraph
+
+# --- Configuration ---
+MONGODB_URI = os.environ.get("MONGODB_URI", "mongodb://localhost:27017")
+DB_NAME = os.environ.get("DB_NAME", "langgraph-test")
+CHECKPOINT_CLXN_NAME = "interrupts_checkpoints"
+WRITES_CLXN_NAME = "interrupts_writes"
+
+
+@pytest.fixture(scope="function")
+def checkpointer_memory() -> Generator[InMemorySaver, None, None]:
+    yield InMemorySaver()
+
+
+@pytest.fixture(scope="function")
+def checkpointer_mongodb() -> Generator[MongoDBSaver, None, None]:
+    with MongoDBSaver.from_conn_string(
+        MONGODB_URI,
+        db_name=DB_NAME,
+        checkpoint_collection_name=CHECKPOINT_CLXN_NAME,
+        writes_collection_name=WRITES_CLXN_NAME,
+    ) as checkpointer:
+        checkpointer.checkpoint_collection.delete_many({})
+        checkpointer.writes_collection.delete_many({})
+        yield checkpointer
+        checkpointer.checkpoint_collection.drop()
+        checkpointer.writes_collection.drop()
+
+
+ALL_CHECKPOINTERS_SYNC = [
+    "checkpointer_memory",
+    "checkpointer_mongodb",
+]
+
+
+@pytest.mark.parametrize("checkpointer_name", ALL_CHECKPOINTERS_SYNC)
+def test(request: pytest.FixtureRequest, checkpointer_name: str) -> None:
+    checkpointer: BaseCheckpointSaver = request.getfixturevalue(checkpointer_name)
+    assert isinstance(checkpointer, BaseCheckpointSaver)
+
+    # --- State Definition ---
+    class State(TypedDict):
+        value: int
+        step: int
+
+    # --- Node Definitions ---
+    def node_inc(state: State) -> State:
+        """Increments value and step by 1"""
+        current_step = state.get("step", 0)
+        return {"value": state["value"] + 1, "step": current_step + 1}
+
+    def node_double(state: State) -> State:
+        """Doubles value and increments step by 1"""
+        current_step = state.get("step", 0)
+        return {"value": state["value"] * 2, "step": current_step + 1}
+
+    # --- Graph Construction ---
+    builder = StateGraph(State)
+    builder.add_node("increment", node_inc)
+    builder.add_node("double", node_double)
+    builder.set_entry_point("increment")
+    builder.add_edge("increment", "double")
+    builder.add_edge("double", END)
+
+    # --- Compile Graph (with Interruption) ---
+    # Using sync for simplicity in this demo
+    graph: CompiledGraph = builder.compile(
+        checkpointer=checkpointer, interrupt_after=["increment"]
+    )
+
+    # --- Configure  ---
+    config: RunnableConfig = {"configurable": {"thread_id": "thread_#1"}}
+    initial_input = {"value": 10, "step": 0}
+
+    # --- 1st invoke, with Interruption
+    interrupted_state = graph.invoke(initial_input, config=config)
+    assert interrupted_state == {"value": 10 + 1, "step": 1}
+    state_history = list(graph.get_state_history(config))
+    assert len(state_history) == 3
+    # The states are returned in reverse chronological order.
+    assert state_history[0].next == ("double",)
+
+    # --- 2nd invoke, with input=None, and original config ==> continues from point of interruption
+    final_state = graph.invoke(None, config=config)
+    assert final_state == {"value": (10 + 1) * 2, "step": 2}
+    state_history = list(graph.get_state_history(config))
+    assert len(state_history) == 4
+    assert state_history[0].next == ()
+    assert state_history[-1].next == ("__start__",)
+
+    # --- 3rd invoke, but with an input ===> the CompiledGraph is restarted.
+    new_input = {"value": 100, "step": -100}
+    third_state = graph.invoke(new_input, config=config)
+    assert third_state == {"value": 101, "step": -99}
+
+    # The entire state history is preserved however
+    state_history = list(graph.get_state_history(config))
+    assert len(state_history) == 7
+    assert state_history[0].next == ("double",)
+    assert state_history[2].next == ("__start__",)
+
+    # --- Upstate state and continue from interrupt
+    updated_state = {"value": 1000, "step": 1000}
+    updated_config = graph.update_state(config, updated_state)
+    final_state = graph.invoke(input=None, config=updated_config)
+    assert final_state == {"value": 2000, "step": 1001}