ExecuteScriptAsync doesn't return fetch PromiseResult

[ninoxscutulata]

Version
SDK: 1.0.1189-prerelease
Runtime: 99.0.1150.36
Framework: WInForms
OS: Win10

Repro Steps

string resp1 = await webView.CoreWebView2.ExecuteScriptAsync("async function abc () { let response = await fetch('https://www.yahoo.com/tdv2_fp/api/resource/WeatherLocationService.favoriteLocation?lang=en-US&region=US&site=fp&ssl=1&crumb=N2/kCEJVXBm&returnMeta=true'); let text = await response.json();  return text;} await abc();");
string resp2 = await webView.CoreWebView2.ExecuteScriptAsync("async function abc () { let response = await fetch('https://www.yahoo.com/tdv2_fp/api/resource/WeatherLocationService.favoriteLocation?lang=en-US&region=US&site=fp&ssl=1&crumb=N2/kCEJVXBm&returnMeta=true'); let text = await response.json();  return text;} abc();");
      
Debug.WriteLine(resp1); // "null"
Debug.WriteLine(resp2); // "{}"
      
  // expected response
  // {"data":[],"meta":{}}

In the real Chrome or Edge WebBrowser Devtools Console or chrome webdriver, this script works fine.
But it doesn't work in WebView2.

I think that webview2 should also return a string response because I get a successful string response using a different kind of webdriver, but this is just my guess.

Maybe I don't know how to use it
Is there a way to return the response contents using fetch in webview2?

[champnic]

Hey @ninoxscutulata - thanks for the bug report, and sorry you are running into this. Unfortunately we don't have great support yet for getting async results from a script using ExecuteScriptAsync. The easiest work is to probably have the script send a web message and listen for it using WebMessageReceived when the work is complete. (edit: please see amaitlands comment below for a better workaround) Thanks!

[amaitland]

An alternative is to use the DevTools protocol to evaluate your JavaScript. WebView2 already has support for this. The relevant DevTools method is https://chromedevtools.github.io/devtools-protocol/tot/Runtime/#method-evaluate

If your interested in a ready made library then check out an example #416 (comment)

[R0Wi]

Was running into the same problem and solved it by using DevTools protocol method Runtime.evaluate (see https://gist.github.com/R0Wi/e1266fa4ca0dfa5a65a5f05c188f18b6 for a working example).

Alternatively you could use the NuGet package Microsoft.Web.WebView2.DevToolsProtocolExtension. The method Microsoft.Web.WebView2.Core.DevToolsProtocolExtension.DevToolsProtocolHelper.Runtime.EvaluateAsync will behave the same way under the hood but the package adds a few more dependencies to your project.

[CocoDico78]

Are there any chances of getting this reopened? Are Promsies now supported by ExecuteScriptAsyncExecuteScriptWithResultAsync`?