refactor(mcp): improve config loading to read from app.config first

Update MCP config loading to properly read from Flask app.config
before falling back to defaults. This allows users to override
MCP settings in their superset_config.py file.

- Refactor get_mcp_config() to accept app_config parameter
- Use Pythonic dict unpacking for cleaner config merging
- Add type hints with modern union syntax
- Update flask_singleton.py to pass app.config to get_mcp_config()

Author: aminghadersohi

superset/mcp_service/flask_singleton.py

@@ -39,11 +39,9 @@
     # Create the Flask app instance - this is the singleton
     app = create_app()
 
-    # Apply MCP-specific defaults to app.config if not already set
-    mcp_config = get_mcp_config()
-    for key, value in mcp_config.items():
-        if key not in app.config:
-            app.config[key] = value
+    # Apply MCP configuration - reads from app.config first, falls back to defaults
+    mcp_config = get_mcp_config(app.config)
+    app.config.update(mcp_config)
 
     logger.info("Flask app instance created successfully")
 

superset/mcp_service/mcp_config.py

@@ -73,29 +73,49 @@ def generate_secret_key() -> str:
     return secrets.token_urlsafe(42)
 
 
-def get_mcp_config() -> Dict[str, Any]:
-    """Get complete MCP configuration dictionary"""
-    config = {}
-
-    # Add MCP-specific settings
-    config.update(
-        {
-            "MCP_ADMIN_USERNAME": MCP_ADMIN_USERNAME,
-            "MCP_DEV_USERNAME": MCP_DEV_USERNAME,
-            "SUPERSET_WEBSERVER_ADDRESS": SUPERSET_WEBSERVER_ADDRESS,
-            "WEBDRIVER_BASEURL": WEBDRIVER_BASEURL,
-            "WEBDRIVER_BASEURL_USER_FRIENDLY": WEBDRIVER_BASEURL_USER_FRIENDLY,
-            "MCP_SERVICE_HOST": MCP_SERVICE_HOST,
-            "MCP_SERVICE_PORT": MCP_SERVICE_PORT,
-            "MCP_DEBUG": MCP_DEBUG,
-        }
-    )
-
-    # Add session and CSRF config
-    config.update(MCP_SESSION_CONFIG)
-    config.update(MCP_CSRF_CONFIG)
-
-    return config
+def get_mcp_config(app_config: Dict[str, Any] | None = None) -> Dict[str, Any]:
+    """
+    Get complete MCP configuration dictionary.
+
+    Reads from app_config first, then falls back to defaults if values are not provided.
+
+    Args:
+        app_config: Optional Flask app configuration dict to read values from
+    """
+    app_config = app_config or {}
+
+    # Default MCP configuration
+    defaults = {
+        "MCP_ADMIN_USERNAME": MCP_ADMIN_USERNAME,
+        "MCP_DEV_USERNAME": MCP_DEV_USERNAME,
+        "SUPERSET_WEBSERVER_ADDRESS": SUPERSET_WEBSERVER_ADDRESS,
+        "WEBDRIVER_BASEURL": WEBDRIVER_BASEURL,
+        "WEBDRIVER_BASEURL_USER_FRIENDLY": WEBDRIVER_BASEURL_USER_FRIENDLY,
+        "MCP_SERVICE_HOST": MCP_SERVICE_HOST,
+        "MCP_SERVICE_PORT": MCP_SERVICE_PORT,
+        "MCP_DEBUG": MCP_DEBUG,
+        **MCP_SESSION_CONFIG,
+        **MCP_CSRF_CONFIG,
+    }
+
+    # Merge app_config over defaults - app_config takes precedence
+    return {**defaults, **{k: v for k, v in app_config.items() if k in defaults}}
+
+
+def get_mcp_config_with_overrides(
+    app_config: Dict[str, Any] | None = None,
+) -> Dict[str, Any]:
+    """
+    Alternative approach: Allow any app_config keys, not just predefined ones.
+
+    This version lets users add custom MCP config keys in superset_config.py
+    that aren't predefined in the defaults.
+    """
+    app_config = app_config or {}
+    defaults = get_mcp_config()
+
+    # Start with defaults, then overlay any app_config values
+    return {**defaults, **app_config}
 
 
 def get_mcp_factory_config() -> Dict[str, Any]: