NSURLsessionDelegate issues

[Maddy79]

Steps to Reproduce

1. Create a class that derives from NSURLProtocol and NSURLSession delegate interfaces:
   Ex: public partial class TestUrlProtocol : NSUrlProtocol, INSUrlSessionDelegate, INSUrlSessionTaskDelegate, INSUrlSessionDataDelegate

2. In StartLoading, create the URLSessionTask and resume the task

3. Add delegate methods to handle challenge and redirection

Expected Behavior

This needs to build / run and handle NTLM /certificate challenges

Actual Behavior

First issue:
Gives a warning for the below delegate:
**Warning MT4174: Unable to locate the block to delegate conversion method for the method TestSampleApp.TestUrlProtocol.WillPerformHttpRedirection's parameter #5. (MT4174) Warning

MT4174: Unable to locate the block to delegate conversion method for the method TestSampleApp.TestUrlProtocol.DidReceiveChallenge's parameter #4. (MT4174)**

**And when running this will crash with below error:

Unhandled managed exception: The runtime function get_block_wrapper_creator has been linked away. (ObjCRuntime.RuntimeException)
Crash is pointing at DidReceiveChallenge call.**

Environment

=== Visual Studio Enterprise 2019 for Mac ===

Version 8.1.3 (build 19)
Installation UUID: 5bba6d13-ac9c-4c7c-b27c-1f9467a37562
GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 5.6.0.25 (d16-0 / 50f7527)

Package version: 518010028

=== Mono Framework MDK ===

Runtime:
Mono 5.18.1.28 (2018-08/223ea7ef92e) (64-bit)
Package version: 518010028

=== NuGet ===

Version: 5.0.2.5988

=== .NET Core ===

Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
2.1.11
2.1.9
2.1.8
2.1.2
2.1.1
SDK: /usr/local/share/dotnet/sdk/2.1.700/Sdks
SDK Versions:
2.1.700
2.1.505
2.1.504
2.1.302
2.1.301
MSBuild SDKs: /Library/Frameworks/Mono.framework/Versions/5.18.1/lib/mono/msbuild/Current/bin/Sdks

=== Xamarin.Profiler ===

Version: 1.6.10
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

=== Updater ===

Version: 11

=== Apple Developer Tools ===

Xcode 10.2.1 (14490.122)
Build 10E1001

=== Xamarin.Mac ===

Version: 5.10.0.157 (Visual Studio Enterprise)
Hash: 6bd9475
Branch: d16-1
Build date: 2019-06-12 17:28:48-0400

=== Xamarin.iOS ===

Version: 12.10.0.157 (Visual Studio Enterprise)
Hash: 6bd9475
Branch: d16-1
Build date: 2019-06-12 17:28:47-0400

=== Xamarin.Android ===

Version: 9.3.0.23 (Visual Studio Enterprise)
Commit: HEAD/d0b48056f
Android SDK: /Users/mbhattathiri/Library/Developer/Xamarin/android-sdk-macosx
Supported Android versions:
7.1 (API level 25)
8.0 (API level 26)
8.1 (API level 27)

SDK Tools Version: 26.1.1
SDK Platform Tools Version: 28.0.1
SDK Build Tools Version: 27.0.3

Build Information:
Mono: mono/mono@3a07bd426d3
Java.Interop: xamarin/java.interop/d16-1@5ddc3e3
LibZipSharp: grendello/LibZipSharp/d16-1@44de300
LibZip: nih-at/libzip@b95cf3f
ProGuard: xamarin/proguard@905836d
SQLite: xamarin/sqlite@8212a2d
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-1@acabd26

=== Microsoft Mobile OpenJDK ===

Java SDK: /Users/mbhattathiri/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_1.8.0.25
1.8.0-25
Android Designer EPL code available here:
https://github.com/xamarin/AndroidDesigner.EPL

=== Android Device Manager ===

Version: 1.2.0.44
Hash: aac645b
Branch: remotes/origin/d16-1
Build date: 2019-05-29 19:55:24 UTC

=== Xamarin Designer ===

Version: 16.1.0.467
Hash: f1657e133
Branch: remotes/origin/d16-1-new-document-model
Build date: 2019-06-18 21:57:42 UTC

=== Xamarin Inspector ===

Version: 1.4.3
Hash: db27525
Branch: 1.4-release
Build date: Mon, 09 Jul 2018 21:20:18 GMT
Client compatibility: 1

=== Build Information ===

Release ID: 801030019
Git revision: 2d04b0145da8aa946d2cc9898fe2a59484e4f3f4
Build date: 2019-06-26 15:34:25+00
Build branch: release-8.1
Xamarin extensions: de240bddd6d1f96bfb1e7d11ce7ac5398956fe1d

=== Operating System ===

Mac OS X 10.14.5
Darwin 18.6.0 Darwin Kernel Version 18.6.0
Thu Apr 25 23:16:27 PDT 2019
root:xnu-4903.261.4~2/RELEASE_X86_64 x86_64

Build Logs

Example Project (If Possible)

[spouliot]

From the warnings/errors it looks like your delegate code is incorrect. Please attach a self-contained test case so we can have a look at the implementation.

It's likely easier to use https://github.com/xamarin/xamarin-macios/blob/master/src/Foundation/NSUrlSessionHandler.cs with HttpClient if you want to use the native NSURLSession API.

[Maddy79]

@spouliot
Attached test app. If http is used it is loading fine, issue is when using https and then it needs to call the challenge delegates.
https://drive.google.com/file/d/1h5m6A-YIrjQwcoEXa-qKekBloo_n2Yya/view?usp=sharing

[spouliot]

Thanks for the sample. Your issue is that you cannot override (ObjC) block-based arguments without some extra glue code.

E.g. this is how WillPerformHttpRedirection is declared in Xamarin.iOS.dll

[Export ("URLSession:task:willPerformHTTPRedirection:newRequest:completionHandler:")]
[BindingImpl (BindingImplOptions.GeneratedCode | BindingImplOptions.Optimizable)]
public unsafe virtual void WillPerformHttpRedirection (NSUrlSession session, NSUrlSessionTask task, NSHttpUrlResponse response, NSUrlRequest newRequest, [BlockProxy (typeof (ObjCRuntime.Trampolines.NIDActionArity1V1))]global::System.Action<NSUrlRequest> completionHandler)

The [BlockProxy] attribute points to extra code that will ensure a correct transition between ObjC and managed code.

This glue code is provided automatically if you use (or override) existing bindings - but if you declare the [Export] manually then you need to do the full job (and manually provide the required glue code).

This is not trivial so you can try to copy/paste existing code (it's largely internal) from Xamarin.iOS.dll into your application.

However I would suggest you to use HttpClient with the NSUrlSessionHandler since it will require a lot less code and ease code sharing across platforms.

[Maddy79]

@spouliot , thanks for looking into this. My requirement is to handle all the challenges (NTLM/Basic/ClientCertificate/ServerTrust) from my code , so I was doing this, which used to work till sometime back. Can you point me where I can get the code for this from Xamarin.iOS.dll?

[spouliot]

Upon re-examination (by @rolfbjarne ) it's actually a supported scenario (i.e. it should work) but there's an issue in the static registrar for inherited interfaces. Re-opening

[spouliot]

@Maddy79 the workaround would be add the [BlockProxy] attributes and copy/paste the source code (of the type referenced) into your application.

Sadly the Trampolines.g.cs file is generated code that is not shipped (like others) inside the package (filed as #6507) but you can use the VS assembly browser to disassemble/decompile it back to C#.

[Maddy79]

@spouliot , yea when I tried using the BlockProxy , I did get the accessibility error for trampolines.
Will check the decompile option, is there any possibility of getting the issue fix in any upcoming release?

[spouliot]

yes, it will be fixed in a future release - but I cannot say when it will be released (even in a preview).

Still it will be available (as an untested package, directly from our build bots) soon after this bug is closed (and you'll get a notification when that happens)

[Maddy79]

@spouliot , is the fix available in the Preview builds of VS (Mac)?

[hmeng7]

Want to check on this to see if this fix is available now since the thread was closed 16 days ago as of the post. Thanks!

[rolfbjarne]

The fix is currently available in our Xcode 11 preview channel. It will also be included in an upcoming update to the existing preview release in our Alpha/Beta channels.