fetch: avoid async function in mainFetch to generate response (#3605)

Author: Uzlopak

lib/web/fetch/index.js

@@ -573,53 +573,46 @@ async function mainFetch (fetchParams, recursive = false) {
   // 11. If response is null, then set response to the result of running
   // the steps corresponding to the first matching statement:
   if (response === null) {
-    response = await (async () => {
-      const currentURL = requestCurrentURL(request)
-
-      if (
-        // - request’s current URL’s origin is same origin with request’s origin,
-        //   and request’s response tainting is "basic"
-        (sameOrigin(currentURL, request.url) && request.responseTainting === 'basic') ||
-        // request’s current URL’s scheme is "data"
-        (currentURL.protocol === 'data:') ||
-        // - request’s mode is "navigate" or "websocket"
-        (request.mode === 'navigate' || request.mode === 'websocket')
-      ) {
-        // 1. Set request’s response tainting to "basic".
-        request.responseTainting = 'basic'
-
-        // 2. Return the result of running scheme fetch given fetchParams.
-        return await schemeFetch(fetchParams)
-      }
-
-      // request’s mode is "same-origin"
-      if (request.mode === 'same-origin') {
-        // 1. Return a network error.
-        return makeNetworkError('request mode cannot be "same-origin"')
-      }
-
-      // request’s mode is "no-cors"
-      if (request.mode === 'no-cors') {
-        // 1. If request’s redirect mode is not "follow", then return a network
-        // error.
-        if (request.redirect !== 'follow') {
-          return makeNetworkError(
-            'redirect mode cannot be "follow" for "no-cors" request'
-          )
-        }
-
+    const currentURL = requestCurrentURL(request)
+    if (
+      // - request’s current URL’s origin is same origin with request’s origin,
+      //   and request’s response tainting is "basic"
+      (sameOrigin(currentURL, request.url) && request.responseTainting === 'basic') ||
+      // request’s current URL’s scheme is "data"
+      (currentURL.protocol === 'data:') ||
+      // - request’s mode is "navigate" or "websocket"
+      (request.mode === 'navigate' || request.mode === 'websocket')
+    ) {
+      // 1. Set request’s response tainting to "basic".
+      request.responseTainting = 'basic'
+
+      // 2. Return the result of running scheme fetch given fetchParams.
+      response = await schemeFetch(fetchParams)
+
+    // request’s mode is "same-origin"
+    } else if (request.mode === 'same-origin') {
+      // 1. Return a network error.
+      response = makeNetworkError('request mode cannot be "same-origin"')
+
+    // request’s mode is "no-cors"
+    } else if (request.mode === 'no-cors') {
+      // 1. If request’s redirect mode is not "follow", then return a network
+      // error.
+      if (request.redirect !== 'follow') {
+        response = makeNetworkError(
+          'redirect mode cannot be "follow" for "no-cors" request'
+        )
+      } else {
         // 2. Set request’s response tainting to "opaque".
         request.responseTainting = 'opaque'
 
         // 3. Return the result of running scheme fetch given fetchParams.
-        return await schemeFetch(fetchParams)
-      }
-
-      // request’s current URL’s scheme is not an HTTP(S) scheme
-      if (!urlIsHttpHttpsScheme(requestCurrentURL(request))) {
-        // Return a network error.
-        return makeNetworkError('URL scheme must be a HTTP(S) scheme')
+        response = await schemeFetch(fetchParams)
       }
+    // request’s current URL’s scheme is not an HTTP(S) scheme
+    } else if (!urlIsHttpHttpsScheme(requestCurrentURL(request))) {
+      // Return a network error.
+      response = makeNetworkError('URL scheme must be a HTTP(S) scheme')
 
       // - request’s use-CORS-preflight flag is set
       // - request’s unsafe-request flag is set and either request’s method is
@@ -633,13 +626,14 @@ async function mainFetch (fetchParams, recursive = false) {
       //    4. Return corsWithPreflightResponse.
       // TODO
 
-      // Otherwise
+    // Otherwise
+    } else {
       //    1. Set request’s response tainting to "cors".
       request.responseTainting = 'cors'
 
       //    2. Return the result of running HTTP fetch given fetchParams.
-      return await httpFetch(fetchParams)
-    })()
+      response = await httpFetch(fetchParams)
+    }
   }
 
   // 12. If recursive is true, then return response.