fix: preserve S3 XML error codes

Author: cxymds

contexts/s3-context.tsx

@@ -5,13 +5,47 @@ import { useRouter } from "next/navigation"
 import { S3Client } from "@aws-sdk/client-s3"
 import { useAuth } from "@/contexts/auth-context"
 import { configManager } from "@/lib/config"
+import { getServiceErrorMessage, getXmlErrorMessage } from "@/lib/error-handler"
 import type { SiteConfig } from "@/types/config"
 
 interface S3Response {
   response?: { body?: string }
   [key: string]: unknown
 }
 
+type StreamCollector = (streamBody: unknown) => Promise<Uint8Array>
+
+const readResponseBodyText = async (
+  body: unknown,
+  streamCollector: StreamCollector | undefined,
+): Promise<string | null> => {
+  if (typeof body === "string") {
+    return body
+  }
+
+  if (body instanceof Uint8Array) {
+    return new TextDecoder("utf-8").decode(body)
+  }
+
+  if (!body || !streamCollector) {
+    return null
+  }
+
+  const bytes = await streamCollector(body)
+  return new TextDecoder("utf-8").decode(bytes)
+}
+
+const createS3ServiceError = (message: string, statusCode: number) => {
+  const error = new Error(message) as Error & {
+    Code?: string
+    $metadata?: { httpStatusCode?: number }
+  }
+  error.name = message
+  error.Code = message
+  error.$metadata = { httpStatusCode: statusCode }
+  return error
+}
+
 function patchReplicationBody(
   body: string | undefined,
   config: { Rules?: Array<{ DeleteReplication?: { Status?: string } }> } | undefined,
@@ -95,6 +129,31 @@ export function S3Provider({ children }: { children: React.ReactNode }) {
         }) as any,
         { step: "serialize", name: "injectDeleteReplication", priority: "low" },
       )
+      client.middlewareStack.addRelativeTo(
+        ((next: any) => async (args: any) => {
+          const result = await next(args)
+          const response = result?.response
+          const statusCode = response?.statusCode
+
+          if (typeof statusCode === "number" && statusCode >= 300) {
+            const streamCollector = client.config.streamCollector as StreamCollector | undefined
+            const bodyText = await readResponseBodyText(response.body, streamCollector)
+            const errorMessage = bodyText ? (getXmlErrorMessage(bodyText) ?? bodyText.trim()) : null
+
+            if (errorMessage) {
+              throw createS3ServiceError(errorMessage, statusCode)
+            }
+          }
+
+          return result
+        }) as any,
+        {
+          name: "normalizeXmlErrorResponse",
+          relation: "after",
+          toMiddleware: "deserializerMiddleware",
+          override: true,
+        },
+      )
       client.middlewareStack.add(
         ((next: any) => async (args: any) => {
           try {
@@ -137,8 +196,10 @@ export function S3Provider({ children }: { children: React.ReactNode }) {
                 return { response: { statusCode: 401, headers: {} } }
               }
             }
-            if (err?.Code) {
-              throw new Error(err.Code)
+
+            const serviceErrorMessage = getServiceErrorMessage(error)
+            if (serviceErrorMessage) {
+              throw new Error(serviceErrorMessage)
             }
             throw error
           }

lib/error-handler.ts

@@ -5,6 +5,96 @@ export interface ApiError {
   originalError?: Error
 }
 
+const GENERIC_ERROR_MESSAGES = new Set(["error", "unknown", "unknownerror"])
+
+const normalizeErrorText = (value: unknown): string | null => {
+  if (typeof value !== "string") {
+    return null
+  }
+
+  const trimmed = value.trim()
+  return trimmed ? trimmed : null
+}
+
+const isSpecificErrorText = (value: string | null): value is string => {
+  return !!value && !GENERIC_ERROR_MESSAGES.has(value.toLowerCase())
+}
+
+const getXmlTagText = (xml: string, tagName: string): string | null => {
+  const match = xml.match(new RegExp(`<${tagName}[^>]*>([\\s\\S]*?)</${tagName}>`, "i"))
+  return normalizeErrorText(match?.[1])
+}
+
+export const getXmlErrorMessage = (xml: string): string | null => {
+  const trimmed = xml.trim()
+  if (!trimmed.startsWith("<")) {
+    return null
+  }
+
+  const code = getXmlTagText(trimmed, "Code")
+  if (isSpecificErrorText(code)) {
+    return code
+  }
+
+  const message = getXmlTagText(trimmed, "Message") ?? getXmlTagText(trimmed, "Error")
+  if (isSpecificErrorText(message)) {
+    return message
+  }
+
+  return code ?? message
+}
+
+export const getServiceErrorMessage = (error: unknown): string | null => {
+  if (error instanceof Error) {
+    const directMessage = normalizeErrorText(error.message)
+    if (isSpecificErrorText(directMessage)) {
+      return directMessage
+    }
+  }
+
+  if (!error || typeof error !== "object") {
+    return null
+  }
+
+  const err = error as {
+    Code?: unknown
+    Message?: unknown
+    name?: unknown
+    message?: unknown
+    Error?: {
+      Code?: unknown
+      Message?: unknown
+      message?: unknown
+    }
+  }
+
+  const codeCandidates = [
+    normalizeErrorText(err.Code),
+    normalizeErrorText(err.Error?.Code),
+    normalizeErrorText(err.name),
+  ]
+  const messageCandidates = [
+    normalizeErrorText(err.Message),
+    normalizeErrorText(err.Error?.Message),
+    normalizeErrorText(err.Error?.message),
+    normalizeErrorText(err.message),
+  ]
+
+  for (const candidate of codeCandidates) {
+    if (isSpecificErrorText(candidate)) {
+      return candidate
+    }
+  }
+
+  for (const candidate of messageCandidates) {
+    if (isSpecificErrorText(candidate)) {
+      return candidate
+    }
+  }
+
+  return codeCandidates.find(Boolean) ?? messageCandidates.find(Boolean) ?? null
+}
+
 export class ConfigLoadError extends Error {
   code: "INVALID_URL" | "STORAGE_ERROR" | "NETWORK_ERROR" | "UNKNOWN_ERROR"
   originalError?: Error
@@ -26,8 +116,7 @@ export const parseApiError = async (response: Response): Promise<string> => {
       const text = await response.clone().text()
       if (text) {
         if (text.trim().startsWith("<")) {
-          const match = text.match(/<Message>(.*?)<\/Message>/i) || text.match(/<Error>(.*?)<\/Error>/i)
-          return match?.[1] ?? text
+          return getXmlErrorMessage(text) ?? text
         }
         return text
       }

tests/lib/error-handler.test.ts

@@ -0,0 +1,44 @@
+import test from "node:test"
+import assert from "node:assert/strict"
+
+const loadErrorHandler = () => import(new URL("../../lib/error-handler.ts", import.meta.url).href)
+
+test("getServiceErrorMessage prefers a specific error code over UnknownError", async () => {
+  const { getServiceErrorMessage } = await loadErrorHandler()
+  const error = {
+    name: "UnknownError",
+    message: "UnknownError",
+    Error: {
+      Code: "InvalidBucketName",
+      Message: "The specified bucket is not valid.",
+    },
+  }
+
+  assert.equal(getServiceErrorMessage(error), "InvalidBucketName")
+})
+
+test("getServiceErrorMessage falls back to a specific nested message when the code is generic", async () => {
+  const { getServiceErrorMessage } = await loadErrorHandler()
+  const error = {
+    name: "UnknownError",
+    message: "UnknownError",
+    Error: {
+      Code: "UnknownError",
+      Message: "Bucket names cannot contain Chinese characters.",
+    },
+  }
+
+  assert.equal(getServiceErrorMessage(error), "Bucket names cannot contain Chinese characters.")
+})
+
+test("getServiceErrorMessage keeps plain Error messages intact", async () => {
+  const { getServiceErrorMessage } = await loadErrorHandler()
+  assert.equal(getServiceErrorMessage(new Error("network timeout")), "network timeout")
+})
+
+test("getXmlErrorMessage extracts an error code when the XML has no message", async () => {
+  const { getXmlErrorMessage } = await loadErrorHandler()
+  const xml = '<?xml version="1.0" encoding="UTF-8"?><Error><Code>InvalidBucketName</Code></Error>'
+
+  assert.equal(getXmlErrorMessage(xml), "InvalidBucketName")
+})