[dotnet] Set the default RuntimeIdentifier for publishing scenarios. (#24329)

Ref: dotnet/sdk#27253

Author: rolfbjarne

dotnet/targets/Xamarin.Shared.Sdk.props

@@ -137,6 +137,12 @@
 
 	</PropertyGroup>
 
+	<!-- Set the default RuntimeIdentifier when publishing -->
+	<PropertyGroup Condition="'$(PublishRuntimeIdentifier)' == ''">
+		<PublishRuntimeIdentifier Condition="'$(_PlatformName)' == 'iOS'">ios-arm64</PublishRuntimeIdentifier>
+		<PublishRuntimeIdentifier Condition="'$(_PlatformName)' == 'tvOS'">tvos-arm64</PublishRuntimeIdentifier>
+	</PropertyGroup>
+
 	<!-- Now that we know the runtime identifier, we can determine if we're building for a simulator -->
 	<PropertyGroup>
 		<_SdkIsSimulator Condition="$(RuntimeIdentifier.Contains('simulator')) Or $(RuntimeIdentifiers.Contains('simulator'))">true</_SdkIsSimulator>

tests/dotnet/UnitTests/PostBuildTest.cs

@@ -233,5 +233,22 @@ public void PublishFailureTest (ApplePlatform platform, string runtimeIdentifier
 
 			Assert.That (pkgPath, Does.Not.Exist, "ipa/pkg creation");
 		}
+
+		[TestCase (ApplePlatform.iOS, "ios-arm64")]
+		[TestCase (ApplePlatform.TVOS, "tvos-arm64")]
+		public void DefaultPublishRid (ApplePlatform platform, string expectedRuntimeIdentifier)
+		{
+			var project = "MySimpleApp";
+			var configuration = "Release";
+			Configuration.IgnoreIfIgnoredPlatform (platform);
+			Configuration.AssertRuntimeIdentifiersAvailable (platform, expectedRuntimeIdentifier);
+
+			var project_path = GetProjectPath (project, expectedRuntimeIdentifier, platform: platform, out var appPath, configuration: configuration);
+			Clean (project_path);
+
+			var properties = GetDefaultProperties ();
+			var rv = DotNet.AssertPublish (project_path, properties);
+			Assert.That (appPath, Does.Exist, "App existence");
+		}
 	}
 }

tests/xharness/Jenkins/TestVariationsFactory.cs

@@ -229,6 +229,8 @@ public IEnumerable<T> CreateTestVariations<T> (IEnumerable<T> tests, Func<MSBuil
 						if (publishaot) {
 							clone.Xml.SetProperty ("PublishAot", "true", last: false);
 							clone.Xml.SetProperty ("_IsPublishing", "true", last: false); // quack like "dotnet publish", otherwise PublishAot=true has no effect.
+							if (!string.IsNullOrEmpty (runtime_identifer))
+								clone.Xml.SetProperty ("PublishRuntimeIdentifier", runtime_identifer);
 						}
 						if (!string.IsNullOrEmpty (test_variation)) {
 							clone.Xml.SetProperty ("TestVariation", test_variation);