fix: Ensure filename is available for diff rendering in write-file

This commit resolves a bug where the `write-file` operation could fail to render content due to a missing filename.

The fix involves:
- Ensuring `fileName` is consistently passed to `DiffRenderer.tsx` through `ToolConfirmationMessage.tsx`, `ToolMessage.tsx`, and `useGeminiStream.ts`.
- Modifying `edit.ts` and `write-file.ts` to include `fileName` in the `FileDiff` object.
- Expanding the `FileDiff` interface in `tools.ts` to include `fileName`.

Additionally, this commit enhances the diff rendering by:
- Adding syntax highlighting based on file extension in `DiffRenderer.tsx`.
- Adding more language mappings to `getLanguageFromExtension` in `DiffRenderer.tsx`.
- Added lots of tests for all the above.

Fixes https://b.corp.google.com/issues/418125982

3 files changed, 14 insertions, 7 deletions

diff --git a/packages/cli/src/ui/hooks/atCommandProcessor.ts b/packages/cli/src/ui/hooks/atCommandProcessor.ts
index e0cf65c5..e2934840 100644
--- a/packages/cli/src/ui/hooks/atCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/atCommandProcessor.ts
@@ -154,7 +154,9 @@ export async function handleAtCommand({
     if (isNodeError(error) && error.code === 'ENOENT') {
       onDebugMessage(`Path not found, proceeding with original: ${pathSpec}`);
     } else {
-      console.error(`Error stating path ${pathPart}:`, error);
+      console.error(
+        `Error stating path ${pathPart}: ${getErrorMessage(error)}`,
+      );
       onDebugMessage(
         `Error stating path, proceeding with original: ${pathSpec}`,
       );
@@ -200,7 +202,7 @@ export async function handleAtCommand({
     );
 
     return { processedQuery, shouldProceed: true };
-  } catch (error) {
+  } catch (error: unknown) {
     // Handle errors during tool execution
     toolCallDisplay = {
       callId: `client-read-${userMessageTimestamp}`,
diff --git a/packages/cli/src/ui/hooks/useCompletion.ts b/packages/cli/src/ui/hooks/useCompletion.ts
index 622dc4c4..9c0c2db1 100644
--- a/packages/cli/src/ui/hooks/useCompletion.ts
+++ b/packages/cli/src/ui/hooks/useCompletion.ts
@@ -7,7 +7,12 @@
 import { useState, useEffect, useCallback } from 'react';
 import * as fs from 'fs/promises';
 import * as path from 'path';
-import { isNodeError, escapePath, unescapePath } from '@gemini-code/server';
+import {
+  isNodeError,
+  escapePath,
+  unescapePath,
+  getErrorMessage,
+} from '@gemini-code/server';
 import {
   MAX_SUGGESTIONS_TO_SHOW,
   Suggestion,
@@ -202,7 +207,7 @@ export function useCompletion(
           setActiveSuggestionIndex(filteredSuggestions.length > 0 ? 0 : -1);
           setVisibleStartIndex(0);
         }
-      } catch (error) {
+      } catch (error: unknown) {
         if (isNodeError(error) && error.code === 'ENOENT') {
           // Directory doesn't exist, likely mid-typing, clear suggestions
           if (isMounted) {
@@ -211,8 +216,7 @@ export function useCompletion(
           }
         } else {
           console.error(
-            `Error fetching completion suggestions for ${baseDirAbsolute}:`,
-            error,
+            `Error fetching completion suggestions for ${baseDirAbsolute}: ${getErrorMessage(error)}`,
           );
           if (isMounted) {
             resetCompletionState();
diff --git a/packages/cli/src/ui/hooks/useGeminiStream.ts b/packages/cli/src/ui/hooks/useGeminiStream.ts
index a9aa8d54..29ce313d 100644
--- a/packages/cli/src/ui/hooks/useGeminiStream.ts
+++ b/packages/cli/src/ui/hooks/useGeminiStream.ts
@@ -326,6 +326,7 @@ export const useGeminiStream = (
       if ('fileDiff' in originalDetails) {
         resultDisplay = {
           fileDiff: (originalDetails as ToolEditConfirmationDetails).fileDiff,
+          fileName: (originalDetails as ToolEditConfirmationDetails).fileName,
         };
       } else {
         resultDisplay = `~~${(originalDetails as ToolExecuteConfirmationDetails).command}~~`;
@@ -590,7 +591,7 @@ export const useGeminiStream = (
           addItem(
             {
               type: MessageType.ERROR,
-              text: `[Stream Error: ${getErrorMessage(error)}]`,
+              text: `[Stream Error: ${getErrorMessage(error) || 'Unknown error'}]`,
             },
             userMessageTimestamp,
           );