fix: surface diff fetch failures

Author: taskylizard

server/api/registry/compare-file/[...pkg].get.ts

@@ -39,16 +39,24 @@ async function fetchFileContentForDiff(
   filePath: string,
   signal?: AbortSignal,
 ): Promise<string | null> {
+  const url = `https://cdn.jsdelivr.net/npm/${packageName}@${version}/${filePath}`
+  const controller = new AbortController()
+  const timeoutId = setTimeout(() => controller.abort(), DIFF_TIMEOUT)
+  if (signal) {
+    signal.addEventListener('abort', () => controller.abort(signal.reason as any), { once: true })
+  }
+
   try {
-    const url = `https://cdn.jsdelivr.net/npm/${packageName}@${version}/${filePath}`
-    const response = await fetch(url, { signal })
+    const response = await fetch(url, { signal: controller.signal })
 
     if (!response.ok) {
       if (response.status === 404) return null
-      throw new Error(`Failed to fetch: ${response.status}`)
+      throw createError({
+        statusCode: response.status >= 500 ? 502 : response.status,
+        message: `Failed to fetch file (${response.status})`,
+      })
     }
 
-    // Check content-length
     const contentLength = response.headers.get('content-length')
     if (contentLength && parseInt(contentLength, 10) > MAX_DIFF_FILE_SIZE) {
       throw createError({
@@ -71,7 +79,18 @@ async function fetchFileContentForDiff(
     if (error && typeof error === 'object' && 'statusCode' in error) {
       throw error
     }
-    return null
+    if ((error as Error)?.name === 'AbortError') {
+      throw createError({
+        statusCode: 504,
+        message: 'Diff request timed out while fetching file',
+      })
+    }
+    throw createError({
+      statusCode: 502,
+      message: 'Failed to fetch file for diff',
+    })
+  } finally {
+    clearTimeout(timeoutId)
   }
 }
 
@@ -116,12 +135,15 @@ export default defineCachedEventHandler(
 
     try {
       // Validate inputs
-      const { packageName, fromVersion, toVersion, filePath } = v.parse(PackageFileDiffQuerySchema, {
-        packageName: rawPackageName,
-        fromVersion: range.from,
-        toVersion: range.to,
-        filePath: rawFilePath,
-      })
+      const { packageName, fromVersion, toVersion, filePath } = v.parse(
+        PackageFileDiffQuerySchema,
+        {
+          packageName: rawPackageName,
+          fromVersion: range.from,
+          toVersion: range.to,
+          filePath: rawFilePath,
+        },
+      )
 
       // Set up abort controller for timeout
       const controller = new AbortController()
@@ -178,9 +200,7 @@ export default defineCachedEventHandler(
         }
 
         // Insert skip blocks and count stats
-        const hunkOnly = diff.hunks.filter(
-          (h): h is DiffHunk => h.type === 'hunk',
-        )
+        const hunkOnly = diff.hunks.filter((h): h is DiffHunk => h.type === 'hunk')
         const hunksWithSkips = insertSkipBlocks(hunkOnly)
         const stats = countDiffStats(hunksWithSkips)