UI API called on a background thread iOS 13 using Legacy Authentication

[dunada]

Description

After update Auth0.swift to version 1.17.1 When I hit the login button, the app freezes for a few seconds and the proceeds normally, and I get the following message in the terminal:

=================================================================
Main Thread Checker: UI API called on a background thread: -[UIViewController presentingViewController]
PID: 1180, TID: 314715, Thread name: (none), Queue name: NSOperationQueue 0x10b2210b0 (QOS: UNSPECIFIED), QoS: 0
Backtrace:
4 Auth0 0x00000001088be3dc $s5Auth013SafariWebAuthC03newB0_8callbackSo22SFSafariViewControllerC_yAA6ResultOyAA11CredentialsCGct10Foundation3URLV_yALctFyALcfU_ + 192
5 Auth0 0x000000010889e99c $s5Auth04PKCEV11credentials4from8callbackySDyS2SG_yAA6ResultOyAA11CredentialsCGctFyALcfU_ + 640
6 Auth0 0x00000001088a2f64 $s5Auth06ResultOyAA11CredentialsCGIegg_AFIegn_TR + 36
7 Auth0 0x000000010888ad9c $s5Auth020authenticationObject4from8callbackyAA8ResponseVyAA19AuthenticationErrorCG_yAA6ResultOyxGXEtAA17JSONObjectPayloadRzlFAA11CredentialsC_Tg5 + 332
8 Auth0 0x00000001088b2a70 $s5Auth07RequestV5startyyyAA6ResultOyxGcFy10Foundation4DataVSg_So13NSURLResponseCSgs5Error_pSgtcfU_AA11CredentialsC_AA014AuthenticationH0CTg5 + 280
9 Auth0 0x00000001088b5398 $s5Auth07RequestV5startyyyAA6ResultOyxGcFy10Foundation4DataVSg_So13NSURLResponseCSgs5Error_pSgtcfU_AA11CredentialsC_AA014AuthenticationH0CTg5TA + 32
10 Auth0 0x00000001088b2d6c $s10Foundation4DataVSgSo13NSURLResponseCSgs5Error_pSgIegggg_So6NSDataCSgAGSo7NSErrorCSgIeyByyy_TR + 148
11 Sonic-Inhouse 0x00000001039e7a30 __SplunkNSCFURLSessionDataTaskWithRequestCompletionHandler_block_invoke + 460
12 Dynatrace 0x0000000105e810ec __74-[DTXURLSessionInstrumentation dataTaskWithRequest_DTX:completionHandler:]_block_invoke + 792
13 CFNetwork 0x00000001be1aad7c CFNetServiceBrowserSearchForServices + 93016
14 CFNetwork 0x00000001be1bb2b0 _CFHTTPMessageSetResponseProxyURL + 9540
15 Foundation 0x00000001bb35d65c 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 1132124
16 Foundation 0x00000001bb267448 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 123976
17 Foundation 0x00000001bb35f8e4 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 1140964
18 Foundation 0x00000001bb2670e0 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 123104
19 Foundation 0x00000001bb3602dc 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 1143516
20 Foundation 0x00000001bb35fda8 32C04A3C-D431-351A-AE6A-1D87EE3CFFB6 + 1142184
21 libdispatch.dylib 0x000000010af11298 _dispatch_block_async_invoke2 + 104
22 libdispatch.dylib 0x000000010af02c04 _dispatch_client_callout + 16
23 libdispatch.dylib 0x000000010af05808 _dispatch_continuation_pop + 524
24 libdispatch.dylib 0x000000010af04c88 _dispatch_async_redirect_invoke + 624
25 libdispatch.dylib 0x000000010af14168 _dispatch_root_queue_drain + 376
26 libdispatch.dylib 0x000000010af14a90 _dispatch_worker_thread2 + 156
27 libsystem_pthread.dylib 0x00000001bacb5f64 _pthread_wqthread + 212
28 libsystem_pthread.dylib 0x00000001bacb8ae0 start_wqthread + 8

=================================================================

Environment

• Auth0.swift version 1.17.1
• iOS version 13
• Carthage
• Xcode GM Seed 2

Reproduction

Try to login in iOS 13 with the Auth0 version 1.17.1 using the legacy authentication.

The code I used for that:

func login(params: [String: Any], completion: @escaping (BFFAuthenticable.AuthResult) -> Void) {
    var auth = Auth0
        .webAuth(
            clientId: clientId,
            domain: domain)
        .scope("openid offline_access") //offline_access is required for refresh token...
        .audience(audience)
    let auth0Params: [String: String] = [
        "connection": connection,
        "flow": "login",
        "prompt": "login"
    ]
    
    
    auth = auth.parameters(auth0Params)
    
    if #available(iOS 11.0, *) {
        //Prevent ios 11 from showing a prompt by using `SFSafariViewController` vs. `SFAuthenticationSession`
        auth = auth.useLegacyAuthentication()
    }
    
    auth.start {
        result in
        self.handle(result, completion: completion)
    }
}

[cocojoe]

Please add the information requested in the issue template, it's also not clear was this a crash or was it the UI thread checker which will throw an exception as a warning.

Sounds like auth0/Lock.swift#565 which started in Xcode 11 with iOS 13. Doesn't present in iOS 12.

[dunada]

Sorry @cocojoe I just fixed the description, Yes you are right it looks like the auth0/Lock.swift#565

[colin-chan]

Is this going to be fixed for auth0/Auth0.swift. A fix was released for auth0/Lock.swift (#565) but the same problem hasn't been corrected for this project.