fix(fetch): treat fetch-related TypeError as an AxiosError.ERR_NETWORK error; (#6380)

lib/adapters/fetch.js

@@ -196,13 +196,16 @@ export default isFetchSupported && (async (config) => {
   } catch (err) {
     onFinish();
 
-    let {code} = err;
-
-    if (err.name === 'NetworkError') {
-      code = AxiosError.ERR_NETWORK;
+    if (err && err.name === 'TypeError' && /fetch/i.test(err.message)) {
+      throw Object.assign(
+        new AxiosError('Network Error', AxiosError.ERR_NETWORK, config, request),
+        {
+          cause: err.cause || err
+        }
+      )
     }
 
-    throw AxiosError.from(err, code, config, request);
+    throw AxiosError.from(err, err && err.code, config, request);
   }
 });
 

test/unit/adapters/fetch.js

@@ -370,4 +370,14 @@ describe('supports fetch with nodejs', function () {
 
     assert.strictEqual(data, '/?test=1&foo=1&bar=2');
   });
+
+  it('should handle fetch failed error as an AxiosError with ERR_NETWORK code', async () => {
+    try{
+      await fetchAxios('http://notExistsUrl.in.nowhere');
+      assert.fail('should fail');
+    } catch (err) {
+      assert.strictEqual(String(err), 'AxiosError: Network Error');
+      assert.strictEqual(err.cause && err.cause.code, 'ENOTFOUND');
+    }
+  });
 });