Merge branch 'feature/error-handling'

src/mcp_text_editor/errors.py

@@ -0,0 +1,99 @@
+"""Error handling for MCP Text Editor."""
+from dataclasses import dataclass
+from enum import Enum
+from typing import Any, Dict, Optional
+
+
+class ErrorCode(str, Enum):
+    """Error codes for MCP Text Editor."""
+
+    # Protocol level errors (1000-1999)
+    INVALID_REQUEST = "INVALID_REQUEST"
+    INVALID_SCHEMA = "INVALID_SCHEMA"
+    INVALID_FIELD = "INVALID_FIELD"
+
+    # File operation errors (2000-2999)
+    FILE_NOT_FOUND = "FILE_NOT_FOUND"
+    FILE_ALREADY_EXISTS = "FILE_ALREADY_EXISTS"
+    FILE_ACCESS_DENIED = "FILE_ACCESS_DENIED"
+    FILE_HASH_MISMATCH = "FILE_HASH_MISMATCH"
+
+    # Content operation errors (3000-3999)
+    CONTENT_HASH_MISMATCH = "CONTENT_HASH_MISMATCH"
+    INVALID_LINE_RANGE = "INVALID_LINE_RANGE"
+    CONTENT_TOO_LARGE = "CONTENT_TOO_LARGE"
+
+    # Internal errors (9000-9999)
+    INTERNAL_ERROR = "INTERNAL_ERROR"
+
+
+@dataclass
+class MCPError(Exception):
+    """Base exception class for MCP Text Editor."""
+
+    code: ErrorCode
+    message: str
+    details: Optional[Dict[str, Any]] = None
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert error to dictionary format for JSON response."""
+        error_dict = {
+            "error": {
+                "code": self.code,
+                "message": self.message,
+            }
+        }
+        if self.details:
+            error_dict["error"]["details"] = self.details
+        return error_dict
+
+
+class ValidationError(MCPError):
+    """Raised when input validation fails."""
+
+    def __init__(
+        self,
+        message: str,
+        details: Optional[Dict[str, Any]] = None,
+        code: ErrorCode = ErrorCode.INVALID_SCHEMA,
+    ):
+        super().__init__(code=code, message=message, details=details)
+
+
+class FileOperationError(MCPError):
+    """Raised when file operations fail."""
+
+    def __init__(
+        self,
+        message: str,
+        details: Optional[Dict[str, Any]] = None,
+        code: ErrorCode = ErrorCode.FILE_NOT_FOUND,
+    ):
+        super().__init__(code=code, message=message, details=details)
+
+
+class ContentOperationError(MCPError):
+    """Raised when content operations fail."""
+
+    def __init__(
+        self,
+        message: str,
+        details: Optional[Dict[str, Any]] = None,
+        code: ErrorCode = ErrorCode.CONTENT_HASH_MISMATCH,
+    ):
+        super().__init__(code=code, message=message, details=details)
+
+
+class InternalError(MCPError):
+    """Raised when internal errors occur."""
+
+    def __init__(
+        self,
+        message: str = "An internal error occurred",
+        details: Optional[Dict[str, Any]] = None,
+    ):
+        super().__init__(
+            code=ErrorCode.INTERNAL_ERROR,
+            message=message,
+            details=details,
+        )

src/mcp_text_editor/handlers/base.py

@@ -1,11 +1,36 @@
 """Base handler for MCP Text Editor."""
 
-from typing import Any, Dict, Sequence
+from functools import wraps
+from typing import Any, Dict, Sequence, TypeVar
 
 from mcp.types import TextContent, Tool
 
+from ..errors import MCPError, InternalError, ValidationError
 from ..text_editor import TextEditor
 
+T = TypeVar("T")
+
+
+def handle_errors(func):
+    """Decorator to handle errors in handler methods."""
+
+    @wraps(func)
+    async def wrapper(*args, **kwargs) -> Sequence[TextContent]:
+        try:
+            return await func(*args, **kwargs)
+        except MCPError as e:
+            # Known application errors
+            return [TextContent(text=str(e.to_dict()))]
+        except Exception as e:
+            # Unexpected errors
+            internal_error = InternalError(
+                message="An unexpected error occurred",
+                details={"error": str(e), "type": e.__class__.__name__},
+            )
+            return [TextContent(text=str(internal_error.to_dict()))]
+
+    return wrapper
+
 
 class BaseHandler:
     """Base class for handlers."""
@@ -17,10 +42,52 @@ def __init__(self, editor: TextEditor | None = None):
         """Initialize the handler."""
         self.editor = editor if editor is not None else TextEditor()
 
+    def validate_arguments(self, arguments: Dict[str, Any]) -> None:
+        """Validate the input arguments.
+
+        Args:
+            arguments: The arguments to validate
+
+        Raises:
+            ValidationError: If the arguments are invalid
+        """
+        raise NotImplementedError
+
     def get_tool_description(self) -> Tool:
         """Get the tool description."""
         raise NotImplementedError
 
+    @handle_errors
     async def run_tool(self, arguments: Dict[str, Any]) -> Sequence[TextContent]:
-        """Execute the tool with given arguments."""
+        """Execute the tool with given arguments.
+
+        This method is decorated with handle_errors to provide consistent
+        error handling across all handlers.
+
+        Args:
+            arguments: The arguments for the tool
+
+        Returns:
+            Sequence[TextContent]: The tool's output
+
+        Raises:
+            MCPError: For known application errors
+            Exception: For unexpected errors
+        """
+        # Validate arguments before execution
+        self.validate_arguments(arguments)
+        return await self._execute_tool(arguments)
+
+    async def _execute_tool(self, arguments: Dict[str, Any]) -> Sequence[TextContent]:
+        """Internal method to execute the tool.
+
+        This should be implemented by each handler to provide the actual
+        tool functionality.
+
+        Args:
+            arguments: The validated arguments for the tool
+
+        Returns:
+            Sequence[TextContent]: The tool's output
+        """
         raise NotImplementedError

src/mcp_text_editor/handlers/delete_text_file_contents.py

@@ -18,7 +18,7 @@ class DeleteTextFileContentsHandler(BaseHandler):
     """Handler for deleting content from a text file."""
 
     name = "delete_text_file_contents"
-    description = "Delete specified content ranges from a text file. The file must exist. File paths must be absolute. You need to provide the file_hash comes from get_text_file_contents."
+    description = "Delete specified content ranges from a text file. The file must exist. File paths must be absolute. You need to provide the file_hash comes from get_text_file_contents."  # noqa: E501
 
     def get_tool_description(self) -> Tool:
         """Get the tool description."""
@@ -34,7 +34,7 @@ def get_tool_description(self) -> Tool:
                     },
                     "file_hash": {
                         "type": "string",
-                        "description": "Hash of the file contents for concurrency control. it should be matched with the file_hash when get_text_file_contents is called.",
+                        "description": "Hash of the file contents for concurrency control. it should be matched with the file_hash when get_text_file_contents is called.",  # noqa: E501
                     },
                     "ranges": {
                         "type": "array",
@@ -52,7 +52,7 @@ def get_tool_description(self) -> Tool:
                                 },
                                 "range_hash": {
                                     "type": "string",
-                                    "description": "Hash of the content being deleted. it should be matched with the range_hash when get_text_file_contents is called with the same range.",
+                                    "description": "Hash of the content being deleted. it should be matched with the range_hash when get_text_file_contents is called with the same range.",  # noqa: E501
                                 },
                             },
                             "required": ["start", "range_hash"],

src/mcp_text_editor/handlers/insert_text_file_contents.py

@@ -17,7 +17,7 @@ class InsertTextFileContentsHandler(BaseHandler):
     """Handler for inserting content before or after a specific line in a text file."""
 
     name = "insert_text_file_contents"
-    description = "Insert content before or after a specific line in a text file. Uses hash-based validation for concurrency control. You need to provide the file_hash comes from get_text_file_contents."
+    description = "Insert content before or after a specific line in a text file. Uses hash-based validation for concurrency control. You need to provide the file_hash comes from get_text_file_contents."  # noqa: E501
 
     def get_tool_description(self) -> Tool:
         """Get the tool description."""
@@ -33,7 +33,7 @@ def get_tool_description(self) -> Tool:
                     },
                     "file_hash": {
                         "type": "string",
-                        "description": "Hash of the file contents for concurrency control. it should be matched with the file_hash when get_text_file_contents is called.",
+                        "description": "Hash of the file contents for concurrency control. it should be matched with the file_hash when get_text_file_contents is called.",  # noqa: E501
                     },
                     "contents": {
                         "type": "string",