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fix: handle empty tool response (#8118)

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* handle empty tool response

* Update src/backend/base/langflow/components/tools/mcp_component.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* DataFrame

* fix test

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
This commit is contained in:
Sebastián Estévez 2025-05-21 13:50:18 -04:00 • committed by GitHub
commit 076b228599
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2 changed files with 14 additions and 6 deletions
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12
src/backend/base/langflow/components/tools/mcp_component.py
View file

@ -17,7 +17,7 @@ from langflow.inputs.inputs import InputTypes
from langflow.io import MessageTextInput, MultilineInput, Output, TabInput
from langflow.io.schema import flatten_schema, schema_to_langflow_inputs
from langflow.logging import logger
from langflow.schema import Message
from langflow.schema import DataFrame
def maybe_unflatten_dict(flat: dict[str, Any]) -> dict[str, Any]:
@ -409,7 +409,7 @@ class MCPToolsComponent(Component):
logger.exception(msg)
raise ValueError(msg) from e
async def build_output(self) -> Message:
async def build_output(self) -> DataFrame:
"""Build output with improved error handling and validation."""
try:
await self.update_tools()
@ -426,8 +426,12 @@ class MCPToolsComponent(Component):
output = await exec_tool.coroutine(**unflattened_kwargs)
return Message(text=output.content[len(output.content) - 1].text)
return Message(text="You must select a tool", error=True)
tool_content = []
for item in output.content:
item_dict = item.model_dump()
tool_content.append(item_dict)
return DataFrame(data=tool_content)
return DataFrame(data=[{"error": "You must select a tool"}])
except Exception as e:
msg = f"Error in build_output: {e!s}"
logger.exception(msg)

8
src/backend/tests/unit/components/tools/test_mcp_component.py
View file

@ -108,7 +108,10 @@ class TestMCPToolsComponent(ComponentTestBaseWithoutClient):
# Mock the coroutine response
mock_response = AsyncMock()
mock_response.content = [MagicMock(text="Test response")]
mock_content_item = MagicMock()
mock_content_item.text = "Test response"
mock_content_item.model_dump.return_value = {"text": "Test response"}
mock_response.content = [mock_content_item]
mock_create_coroutine.return_value = AsyncMock(return_value=mock_response)
# Create a mock tool and add it to the cache
@ -126,7 +129,8 @@ class TestMCPToolsComponent(ComponentTestBaseWithoutClient):
mock_get_inputs.return_value = {"test_tool": [mock_input]}
output = await component.build_output()
assert output.text == "Test response"
# Use iloc to access the first row's 'text' column value
assert output.iloc[0]["text"] == "Test response"
# Verify the mocks were called correctly
mock_get_inputs.assert_called_once_with(component.tools)
mock_structured_tool.coroutine.assert_called_once_with(test_param="test value")