fix: prevent parsing empty responses from throwing (#105)

* fix: prevent parsing empty responses from throwing

* fix: guard empty JSON + check length of content

* fix: remove `try/catch`

* fix: adjust error text

Co-authored-by: katspaugh <381895+katspaugh@users.noreply.github.com>

* fix: throw when invalid content

Co-authored-by: katspaugh <381895+katspaugh@users.noreply.github.com>

Author: Aaron Cook

src/utils.ts

@@ -7,6 +7,11 @@ export type ErrorResponse = {
   message: string
 }
 
+const isErrorResponse = (data: unknown): data is ErrorResponse => {
+  const isObject = typeof data === 'object' && data !== null
+  return isObject && 'code' in data && 'message' in data
+}
+
 function replaceParam(str: string, key: string, value: string): string {
   return str.replace(new RegExp(`\\{${key}\\}`, 'g'), value)
 }
@@ -51,16 +56,18 @@ export async function fetchData<T>(url: string, body?: unknown): Promise<T> {
   }
 
   const resp = await fetch(url, options)
-  const json = await resp.json()
+  let json
 
-  if (!resp.ok) {
-    let errTxt = ''
-    try {
-      const err = json as ErrorResponse
-      errTxt = `${err.code}: ${err.message}`
-    } catch (e) {
-      errTxt = resp.statusText
+  try {
+    json = await resp.json()
+  } catch {
+    if (resp.headers && resp.headers.get('content-length') !== '0') {
+      throw new Error(`Invalid response content: ${resp.statusText}`)
     }
+  }
+
+  if (!resp.ok) {
+    const errTxt = isErrorResponse(json) ? `${json.code}: ${json.message}` : resp.statusText
     throw new Error(errTxt)
   }