Add ios pinvoke functional test (#47988)

Contributes to #43865.

Author: MaximLipnin

eng/testing/tests.mobile.targets

@@ -96,6 +96,7 @@
     <PropertyGroup>
       <Optimized>true</Optimized>
       <MainLibraryFileName Condition="'$(MainLibraryFileName)' == ''">AppleTestRunner.dll</MainLibraryFileName>
+      <_MobileIntermediateOutputPath Condition="'$(RunAOTCompilation)' == 'true'">$(IntermediateOutputPath)mobile</_MobileIntermediateOutputPath>
     </PropertyGroup>
     <ItemGroup>
       <AotInputAssemblies Condition="'$(RunAOTCompilation)' == 'true'" Include="$(PublishDir)*.dll" Exclude="$(PublishDir)System.Runtime.WindowsRuntime.dll">
@@ -105,10 +106,13 @@
       <BundleAssemblies Condition="'$(RunAOTCompilation)' != 'true'" Include="$(PublishDir)*.dll" />
     </ItemGroup>
 
+    <MakeDir Directories="$(_MobileIntermediateOutputPath)" 
+             Condition="'$(RunAOTCompilation)' == 'true'"/>
     <RemoveDir Directories="$(BundleDir)" />
 
     <MonoAOTCompiler Condition="'$(RunAOTCompilation)' == 'true'"
         CompilerBinaryPath="$(MicrosoftNetCoreAppRuntimePackNativeDir)cross\$(PackageRID)\mono-aot-cross"
+        OutputDir="$(_MobileIntermediateOutputPath)"
         Mode="Full"
         OutputType="AsmOnly"
         Assemblies="@(AotInputAssemblies)"

src/tasks/AppleAppBuilder/Templates/main-console.m

@@ -64,6 +64,14 @@ - (void)viewDidLoad {
 
 @end
 
+// called from C#
+void
+invoke_external_native_api (void (*callback)(void))
+{
+    if (callback)
+        callback();
+}
+
 // can be called from C# to update UI
 void
 mono_ios_set_summary (const char* value)

src/tests/FunctionalTests/iOS/Simulator/AOT/Program.cs

@@ -9,10 +9,7 @@
 public static class Program
 {
     [DllImport("__Internal")]
-    public extern static void mono_ios_append_output (string value);
-
-    [DllImport("__Internal")]
-    public extern static void mono_ios_set_summary (string value);
+    public static extern void mono_ios_set_summary (string value);
 
     public static async Task<int> Main(string[] args)
     {

src/tests/FunctionalTests/iOS/Simulator/Interpreter/Program.cs

@@ -9,10 +9,7 @@
 public static class Program
 {
     [DllImport("__Internal")]
-    public extern static void mono_ios_append_output (string value);
-
-    [DllImport("__Internal")]
-    public extern static void mono_ios_set_summary (string value);
+    public static extern void mono_ios_set_summary (string value);
 
     public static async Task<int> Main(string[] args)
     {

src/tests/FunctionalTests/iOS/Simulator/PInvoke/Program.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Runtime.InteropServices;
+
+public static class Program
+{
+    [DllImport("__Internal")]
+    unsafe private static extern void invoke_external_native_api(delegate* unmanaged<void> callback);
+
+    private static int counter = 1;
+
+    [UnmanagedCallersOnly]
+    private static void Callback()
+    {
+        counter = 42;
+    }    
+    
+    [DllImport("__Internal")]
+    public static extern void mono_ios_set_summary (string value);
+    
+    public static async Task<int> Main(string[] args)
+    {
+        mono_ios_set_summary($"Starting functional test");
+        unsafe {
+            delegate* unmanaged<void> unmanagedPtr = &Callback;
+            invoke_external_native_api(unmanagedPtr);
+        }
+        Console.WriteLine("Done!");
+        await Task.Delay(5000);
+
+        return counter;
+    }
+}

src/tests/FunctionalTests/iOS/Simulator/PInvoke/iOS.Simulator.PInvoke.Test.csproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <MonoForceInterpreter>true</MonoForceInterpreter>
+    <RunAOTCompilation>false</RunAOTCompilation>
+    <TestRuntime>true</TestRuntime>
+    <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+    <MainLibraryFileName>iOS.Simulator.PInvoke.Test.dll</MainLibraryFileName>
+    <IncludesTestRunner>false</IncludesTestRunner>
+    <ExpectedExitCode>42</ExpectedExitCode>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+  </ItemGroup>
+</Project>