refactor: implement proper typed message for file not found errors

- Add file_not_found_error to clineSays array in message types
- Emit typed file_not_found_error message from readFileTool instead of embedding in XML
- Handle file_not_found_error in ChatRow switch statement
- Remove fragile XML parsing logic for file not found errors
- Maintain consistent error handling pattern with other tool errors like diff_error

Author: roomote

packages/types/src/message.ts

@@ -134,6 +134,7 @@ export function isInteractiveAsk(ask: ClineAsk): ask is InteractiveAsk {
  * - `checkpoint_saved`: Indicates a checkpoint has been saved
  * - `rooignore_error`: Error related to .rooignore file processing
  * - `diff_error`: Error occurred while applying a diff/patch
+ * - `file_not_found_error`: Error when attempting to read a file that doesn't exist
  * - `condense_context`: Context condensation/summarization has started
  * - `condense_context_error`: Error occurred during context condensation
  * - `codebase_search_result`: Results from searching the codebase
@@ -160,6 +161,7 @@ export const clineSays = [
 	"checkpoint_saved",
 	"rooignore_error",
 	"diff_error",
+	"file_not_found_error",
 	"condense_context",
 	"condense_context_error",
 	"codebase_search_result",

src/core/tools/readFileTool.ts

@@ -611,18 +611,30 @@ export async function readFileTool(
 				})
 			} catch (error) {
 				let errorMsg = error instanceof Error ? error.message : String(error)
-				let userFriendlyError = errorMsg
 
 				// Check if this is a file not found error
 				if (error instanceof Error && "code" in error && error.code === "ENOENT") {
-					userFriendlyError = `File not found: The requested file does not exist in the current workspace.`
-				}
+					// Emit a proper typed message for file not found errors
+					await cline.say(
+						"file_not_found_error",
+						JSON.stringify({
+							filePath: relPath,
+							error: "The requested file does not exist in the current workspace.",
+						}),
+					)
 
-				updateFileResult(relPath, {
-					status: "error",
-					error: userFriendlyError,
-					xmlContent: `<file><path>${relPath}</path><error>${userFriendlyError}</error></file>`,
-				})
+					updateFileResult(relPath, {
+						status: "error",
+						error: "File not found",
+						xmlContent: `<file><path>${relPath}</path><error>File not found: The requested file does not exist in the current workspace.</error></file>`,
+					})
+				} else {
+					updateFileResult(relPath, {
+						status: "error",
+						error: errorMsg,
+						xmlContent: `<file><path>${relPath}</path><error>${errorMsg}</error></file>`,
+					})
+				}
 				await handleError(`reading file ${relPath}`, error instanceof Error ? error : new Error(errorMsg))
 			}
 		}
@@ -702,20 +714,35 @@ export async function readFileTool(
 		// Handle all errors using per-file format for consistency
 		const relPath = fileEntries[0]?.path || "unknown"
 		let errorMsg = error instanceof Error ? error.message : String(error)
-		let userFriendlyError = errorMsg
 
 		// Check if this is a file not found error
 		if (error instanceof Error && "code" in error && error.code === "ENOENT") {
-			userFriendlyError = `File not found: The requested file does not exist in the current workspace.`
-		}
+			// Emit a proper typed message for file not found errors
+			await cline.say(
+				"file_not_found_error",
+				JSON.stringify({
+					filePath: relPath,
+					error: "The requested file does not exist in the current workspace.",
+				}),
+			)
 
-		// If we have file results, update the first one with the error
-		if (fileResults.length > 0) {
-			updateFileResult(relPath, {
-				status: "error",
-				error: userFriendlyError,
-				xmlContent: `<file><path>${relPath}</path><error>${userFriendlyError}</error></file>`,
-			})
+			// If we have file results, update the first one with the error
+			if (fileResults.length > 0) {
+				updateFileResult(relPath, {
+					status: "error",
+					error: "File not found",
+					xmlContent: `<file><path>${relPath}</path><error>File not found: The requested file does not exist in the current workspace.</error></file>`,
+				})
+			}
+		} else {
+			// If we have file results, update the first one with the error
+			if (fileResults.length > 0) {
+				updateFileResult(relPath, {
+					status: "error",
+					error: errorMsg,
+					xmlContent: `<file><path>${relPath}</path><error>${errorMsg}</error></file>`,
+				})
+			}
 		}
 
 		await handleError(`reading file ${relPath}`, error instanceof Error ? error : new Error(errorMsg))

webview-ui/src/components/chat/ChatRow.tsx

@@ -1054,23 +1054,14 @@ export const ChatRowContent = ({
 				case "api_req_finished":
 					return null // we should never see this message type
 				case "text":
-					// Check if this is a file not found error from read_file tool
-					if (message.text && message.text.includes("<files>") && message.text.includes("<error>")) {
-						// Parse the XML to extract file path and error message
-						const fileMatch = message.text.match(
-							/<file><path>([^<]+)<\/path><error>([^<]+)<\/error><\/file>/,
-						)
-						if (fileMatch && fileMatch[2].includes("File not found:")) {
-							const filePath = fileMatch[1]
-							return <FileNotFoundError filePath={filePath} />
-						}
-					}
-
 					return (
 						<div>
 							<Markdown markdown={message.text} partial={message.partial} />
 						</div>
 					)
+				case "file_not_found_error":
+					const errorData = safeJsonParse<{ filePath: string; error: string }>(message.text || "{}")
+					return <FileNotFoundError filePath={errorData?.filePath || ""} />
 				case "user_feedback":
 					return (
 						<div className="bg-vscode-editor-background border rounded-xs p-1 overflow-hidden whitespace-pre-wrap">