Improved error handling for the fetch api

lib/bigcommerce/api/utils/errors.ts

@@ -4,12 +4,14 @@ export class BigcommerceGraphQLError extends Error {}
 export class BigcommerceApiError extends Error {
   status: number
   res: Response
+  data: any
 
-  constructor(msg: string, res: Response) {
+  constructor(msg: string, res: Response, data?: any) {
     super(msg)
     this.name = 'BigcommerceApiError'
     this.status = res.status
     this.res = res
+    this.data = data
   }
 }
 

lib/bigcommerce/api/utils/fetch-graphql-api.ts

@@ -23,7 +23,7 @@ export default async function fetchGraphqlApi<Q, V = any>(
   const json = await res.json()
   if (json.errors) {
     console.error(json.errors)
-    throw new Error('Failed to fetch API')
+    throw new Error('Failed to fetch BigCommerce API')
   }
   return json.data
 }

lib/bigcommerce/api/utils/fetch-store-api.ts

@@ -24,13 +24,22 @@ export default async function fetchStoreApi<T>(
     )
   }
 
+  const contentType = res.headers.get('Content-Type')
+  const isJSON = contentType?.includes('application/json')
+
   if (!res.ok) {
-    throw new BigcommerceApiError(await getErrorText(res), res)
+    const data = isJSON ? await res.json() : await getTextOrNull(res)
+    const headers = getRawHeaders(res)
+    const msg = `Big Commerce API error (${
+      res.status
+    }) \nHeaders: ${JSON.stringify(headers, null, 2)}\n${
+      typeof data === 'string' ? data : JSON.stringify(data, null, 2)
+    }`
+
+    throw new BigcommerceApiError(msg, res, data)
   }
 
-  const contentType = res.headers.get('Content-Type')
+  if (!isJSON) {
-
-  if (!contentType?.includes('application/json')) {
     throw new BigcommerceApiError(
       `Fetch to Bigcommerce API failed, expected JSON content but found: ${contentType}`,
       res
@@ -41,12 +50,6 @@ export default async function fetchStoreApi<T>(
   return res.status === 204 ? null : await res.json()
 }
 
-async function getErrorText(res: Response) {
-  return `Big Commerce API error (${res.status}) \n${JSON.stringify(
-    getRawHeaders(res)
-  )}\n ${await getTextOrNull(res)}`
-}
-
 function getRawHeaders(res: Response) {
   const headers: { [key: string]: string } = {}