fix: MCP server update to support partial updates (PATCH semantics)

[iymh]

Description

This PR fixes an issue where updating an MCP server configuration would unintentionally clear existing fields like env and args if they were not included in the request payload.

Reasoning

The endpoint @router.patch("/servers/{server_name}") implies a PATCH operation (partial update). However, the previous implementation performed a full replacement of the configuration object.

This change modifies update_server to merge the new configuration with the existing one, preserving critical fields like env and args when they are not explicitly provided in the update. This aligns the backend behavior with proper PATCH semantics.

CI Fix

Fixed a bash syntax error in typescript_test.yml that occurs when multiple test suites are selected (e.g., @components|@api).

• The grep pattern contained a pipe | character which was interpreted by bash as a pipe operator because it was unquoted.
• Added quotes around the variable to ensure it is treated as a string.

Summary by CodeRabbit

• Bug Fixes
  • Fixed a configuration preservation issue in server updates. When updating an existing server, the system now retains previously configured settings that aren't explicitly modified, preventing unintended loss of environment variables and runtime parameters.

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Walkthrough

The update_server function in the MCP API now inherits missing fields from the existing server configuration during updates. When updating a server, if the new configuration lacks env or args fields but the existing configuration contains them, those fields are preserved from the previous configuration.

Changes

Cohort / File(s)	Summary
Server Update Field Inheritance src/backend/base/langflow/api/v2/mcp.py	Added conditional logic to inherit env and args fields from existing server configuration when they are absent in the new configuration during update operations

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant API as update_server()
    participant Config as Existing Config
    participant NewConfig as New Config

    User->>API: Send update request
    API->>Config: Retrieve existing server config
    Config-->>API: Return existing config
    
    rect rgb(240, 248, 255)
    Note over API: New inheritance logic
    alt existing.env exists AND new.env missing
        API->>NewConfig: Copy env from existing
    end
    alt existing.args exists AND new.args missing
        API->>NewConfig: Copy args from existing
    end
    end
    
    API->>API: Assign updated config to server list
    API->>API: Refresh and upload files
    API-->>User: Return updated server

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Verify the conditional logic correctly identifies missing fields in the new configuration
• Confirm that field inheritance from existing config doesn't cause unintended behavior in edge cases (e.g., when explicitly clearing fields is intended)
• Check that the rest of the update workflow remains unaffected by these additions

Pre-merge checks and finishing touches

❌ Failed checks (1 error, 2 warnings, 2 inconclusive)

Check name	Status	Explanation	Resolution
Test Coverage For New Implementations	❌ Error	No test files found for the PATCH endpoint changes that preserve env and args fields during partial updates.	Add test coverage verifying env/args preservation, override behavior, and backward compatibility for the new PATCH semantics.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.
Test File Naming And Structure	⚠️ Warning	PR modifies critical MCP API update function but includes no test files or test coverage for the PATCH semantics implementation and configuration merging logic.	Add backend test files using test_*.py naming convention with pytest structure covering partial updates, field preservation, edge cases, and both positive/negative scenarios.
Test Quality And Coverage	❓ Inconclusive	Assessment cannot be completed due to inability to access repository code and test files to evaluate implementation changes and test coverage.	Repository must be made accessible in sandbox or provide modified mcp.py file, test files for PATCH endpoint, and test output demonstrating coverage.
Excessive Mock Usage Warning	❓ Inconclusive	Repository access unavailable to analyze test files for excessive mock usage patterns.	Resolve repository access to analyze test infrastructure for mock saturation and verify appropriate mock usage in test files.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title accurately describes the main change: implementing partial updates (PATCH semantics) for MCP server configuration to preserve existing fields like env and args.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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[iymh]

Closing this in favor of #10749