test_on_chain_start_skips_persist_when_defers_inputs() — langchain Function Reference

Source Code

libs/core/tests/unit_tests/tracers/test_langchain.py lines 358–385

def test_on_chain_start_skips_persist_when_defers_inputs() -> None:
    """Test that `_on_chain_start` skips persist when `defers_inputs` is set."""
    client = unittest.mock.MagicMock(spec=Client)
    client.tracing_queue = None
    tracer = LangChainTracer(client=client)

    run_id = UUID("9d878ab3-e5ca-4218-aef6-44cbdc90160a")
    # Pass defers_inputs=True to signal deferred inputs
    tracer.on_chain_start(
        {"name": "test_chain"},
        {"input": ""},
        run_id=run_id,
        defers_inputs=True,
    )

    run = tracer.run_map[str(run_id)]

    persist_called = False

    def mock_persist() -> None:
        nonlocal persist_called
        persist_called = True

    with unittest.mock.patch.object(tracer, "_persist_run_single", mock_persist):
        tracer._on_chain_start(run)

    # Should NOT call persist when defers_inputs is set
    assert not persist_called