feat: ability to run flow without langflow server (#7507)

* flow-runner

* flow-runner

* flow-runner - fix lint

* Update flow_runner.py

* [autofix.ci] apply automated fixes

* Update flow_runner.py

* [autofix.ci] apply automated fixes

* Update flow_runner.py

* [autofix.ci] apply automated fixes

* Update flow_runner.py

* [autofix.ci] apply automated fixes

* CR

* Add docs and require sessionid

* fix lint

* [autofix.ci] apply automated fixes

* refactor: simplify flow ID handling and update class docstring

* refactor: update flow runner import to experimental version

* removed obsolete test

* remove test that use io

* remove another io test

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Edwin Jose <edwin.jose@datastax.com>
Co-authored-by: Jordan Frazier <jordan.frazier@datastax.com>
Co-authored-by: Jordan Frazier <122494242+jordanrfrazier@users.noreply.github.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>

src/backend/tests/unit/services/flow/test_flow_runner.py

@@ -0,0 +1,84 @@
+from uuid import uuid4
+
+import pytest
+from langflow.services.flow.flow_runner import LangflowRunnerExperimental
+
+
+@pytest.fixture
+def sample_flow_dict():
+    return {
+        "data": {
+            "nodes": [],
+            "edges": [],
+        }
+    }
+
+
+@pytest.fixture
+def flow_runner():
+    return LangflowRunnerExperimental()
+
+
+@pytest.mark.asyncio
+async def test_database_exists_check(flow_runner):
+    """Test database exists check functionality."""
+    result = await flow_runner.database_exists_check()
+    assert isinstance(result, bool)
+
+
+@pytest.mark.asyncio
+async def test_get_flow_dict_from_dict(flow_runner, sample_flow_dict):
+    """Test loading flow from a dictionary."""
+    result = await flow_runner.get_flow_dict(sample_flow_dict)
+    assert result == sample_flow_dict
+
+
+@pytest.mark.asyncio
+async def test_get_flow_dict_invalid_input(flow_runner):
+    """Test loading flow with invalid input type."""
+    pattern = r"Input must be a file path .* or a JSON object .*"
+    with pytest.raises(TypeError, match=pattern):
+        await flow_runner.get_flow_dict(123)
+
+
+@pytest.mark.asyncio
+async def test_run_with_dict_input(flow_runner, sample_flow_dict):
+    """Test running flow with dictionary input."""
+    session_id = str(uuid4())
+    input_value = "test input"
+
+    result = await flow_runner.run(
+        flow=sample_flow_dict,
+        input_value=input_value,
+        session_id=session_id,
+    )
+    assert result is not None
+
+
+@pytest.mark.asyncio
+async def test_run_with_different_input_types(flow_runner, sample_flow_dict):
+    """Test running flow with different input and output types."""
+    session_id = str(uuid4())
+    test_cases = [
+        ("text input", "text", "text"),
+        ("chat input", "chat", "chat"),
+        ("test input", "chat", "text"),
+    ]
+
+    for input_value, input_type, output_type in test_cases:
+        result = await flow_runner.run(
+            flow=sample_flow_dict,
+            input_value=input_value,
+            input_type=input_type,
+            output_type=output_type,
+            session_id=session_id,
+        )
+        assert result is not None
+
+
+@pytest.mark.asyncio
+async def test_initialize_database(flow_runner):
+    """Test database initialization."""
+    flow_runner.should_initialize_db = True
+    await flow_runner.init_db_if_needed()
+    assert not flow_runner.should_initialize_db