feat: add SaveToFile component for DataFrame, Data and Message exports (#6114)

* ✨ (save_to_file.py): Add a new component 'SaveToFileComponent' to save DataFrames, Data, or Messages to various file formats. This component allows users to select the input type, file format, and file path for saving the data.

* [autofix.ci] apply automated fixes

* 🔧 (save_to_file.py): refactor variable names for better readability and consistency
🐛 (save_to_file.py): handle unsupported input types and formats by raising ValueErrors with informative error messages

* [autofix.ci] apply automated fixes

* ✨ (test_save_to_file_component.py): Add unit tests for the SaveToFileComponent to ensure proper saving of data to various file formats and handling of different input types.

* [autofix.ci] apply automated fixes

* 📝 (save_to_file.py): Add support for handling different types of message text in the SaveToFileComponent class to ensure proper saving to file
🔧 (test_save_to_file_component.py): Refactor test cases in the SaveToFileComponent test file for better readability and maintainability

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/tests/unit/components/processing/test_save_to_file_component.py

@@ -0,0 +1,165 @@
+import json
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pandas as pd
+import pytest
+from langflow.components.processing.save_to_file import SaveToFileComponent
+from langflow.schema import Data, Message
+
+from tests.base import ComponentTestBaseWithoutClient
+
+
+class TestSaveToFileComponent(ComponentTestBaseWithoutClient):
+    @pytest.fixture(autouse=True)
+    def setup_and_teardown(self):
+        """Setup and teardown for each test."""
+        # Setup
+        test_files = [
+            "./test_output.csv",
+            "./test_output.xlsx",
+            "./test_output.json",
+            "./test_output.md",
+            "./test_output.txt",
+        ]
+        # Teardown
+        yield
+        # Delete test files after each test
+        for file_path in test_files:
+            path = Path(file_path)
+            if path.exists():
+                path.unlink()
+
+    @pytest.fixture
+    def component_class(self):
+        """Return the component class to test."""
+        return SaveToFileComponent
+
+    @pytest.fixture
+    def default_kwargs(self):
+        """Return the default kwargs for the component."""
+        sample_df = pd.DataFrame([{"col1": 1, "col2": "a"}, {"col1": 2, "col2": "b"}])
+        return {"input_type": "DataFrame", "df": sample_df, "file_format": "csv", "file_path": "./test_output.csv"}
+
+    @pytest.fixture
+    def file_names_mapping(self):
+        """Return the file names mapping for different versions."""
+        return []  # New component
+
+    def test_basic_setup(self, component_class, default_kwargs):
+        """Test basic component initialization."""
+        component = component_class()
+        component.set_attributes(default_kwargs)
+        assert component.input_type == "DataFrame"
+        assert component.file_format == "csv"
+        assert component.file_path == "./test_output.csv"
+
+    def test_update_build_config_dataframe(self, component_class):
+        """Test build config update for DataFrame input type."""
+        component = component_class()
+        build_config = {
+            "df": {"show": False},
+            "data": {"show": False},
+            "message": {"show": False},
+            "file_format": {"options": []},
+        }
+
+        updated_config = component.update_build_config(build_config, "DataFrame", "input_type")
+
+        assert updated_config["df"]["show"] is True
+        assert updated_config["data"]["show"] is False
+        assert updated_config["message"]["show"] is False
+        assert set(updated_config["file_format"]["options"]) == set(component.DATA_FORMAT_CHOICES)
+
+    def test_save_message(self, component_class):
+        """Test saving Message to different formats."""
+        test_cases = [
+            ("txt", "Test message"),
+            ("json", json.dumps({"message": "Test message"}, indent=2)),
+            ("markdown", "**Message:**\n\nTest message"),
+        ]
+
+        for fmt, expected_content in test_cases:
+            mock_file = MagicMock()
+            mock_parent = MagicMock()
+            mock_parent.exists.return_value = True
+            mock_file.parent = mock_parent
+            mock_file.expanduser.return_value = mock_file
+
+            # Mock Path at the module level where it's imported
+            with patch("langflow.components.processing.save_to_file.Path") as mock_path:
+                mock_path.return_value = mock_file
+
+                component = component_class()
+                component.set_attributes(
+                    {
+                        "input_type": "Message",
+                        "message": Message(text="Test message"),
+                        "file_format": fmt,
+                        "file_path": f"./test_output.{fmt}",
+                    }
+                )
+
+                result = component.save_to_file()
+
+                mock_file.write_text.assert_called_once_with(expected_content, encoding="utf-8")
+                assert "saved successfully" in result
+
+    def test_save_data(self, component_class):
+        """Test saving Data object to JSON."""
+        test_data = {"col1": ["value1"], "col2": ["value2"]}
+
+        mock_file = MagicMock()
+        mock_parent = MagicMock()
+        mock_parent.exists.return_value = True
+        mock_file.parent = mock_parent
+        mock_file.expanduser.return_value = mock_file
+
+        with patch("langflow.components.processing.save_to_file.Path") as mock_path:
+            mock_path.return_value = mock_file
+
+            component = component_class()
+            component.set_attributes(
+                {
+                    "input_type": "Data",
+                    "data": Data(data=test_data),
+                    "file_format": "json",
+                    "file_path": "./test_output.json",
+                }
+            )
+
+            result = component.save_to_file()
+
+            expected_json = json.dumps(test_data, indent=2)
+            mock_file.write_text.assert_called_once_with(expected_json, encoding="utf-8")
+            assert "saved successfully" in result
+
+    def test_directory_creation(self, component_class, default_kwargs):
+        """Test directory creation if it doesn't exist."""
+        mock_file = MagicMock()
+        mock_parent = MagicMock()
+        mock_parent.exists.return_value = False
+        mock_file.parent = mock_parent
+        mock_file.expanduser.return_value = mock_file
+
+        with patch("langflow.components.processing.save_to_file.Path") as mock_path:
+            mock_path.return_value = mock_file
+            with patch.object(pd.DataFrame, "to_csv") as mock_to_csv:
+                component = component_class()
+                component.set_attributes(default_kwargs)
+
+                result = component.save_to_file()
+
+                mock_parent.mkdir.assert_called_once_with(parents=True, exist_ok=True)
+                assert mock_to_csv.called
+                assert "saved successfully" in result
+
+    def test_invalid_input_type(self, default_kwargs):
+        """Test handling of invalid input type."""
+        component = SaveToFileComponent()
+        invalid_kwargs = default_kwargs.copy()  # Create a copy to modify
+        invalid_kwargs["input_type"] = "InvalidType"
+        component.set_attributes(invalid_kwargs)
+
+        with pytest.raises(ValueError, match="Unsupported input type"):
+            component.save_to_file()