Add runtime property HOSTFXR_PATH

src/installer/tests/Assets/TestProjects/RuntimeProperties/Program.cs

@@ -14,6 +14,13 @@ public static void Main(string[] args)
 
             foreach (string propertyName in args)
             {
+                var propertyValue = (string)System.AppContext.GetData(propertyName);
+                if (string.IsNullOrEmpty(propertyValue))
+                {
+                    Console.WriteLine($"Property '{propertyName}' was not found.");
+                    continue;
+                }
+
                 Console.WriteLine($"AppContext.GetData({propertyName}) = {System.AppContext.GetData(propertyName)}");
             }
         }

src/installer/tests/HostActivation.Tests/RuntimeProperties.cs

@@ -25,9 +25,7 @@ public void AppConfigProperty_AppCanGetData()
             var dotnet = fixture.BuiltDotnet;
             var appDll = fixture.TestProject.AppDll;
             dotnet.Exec(appDll, sharedState.AppTestPropertyName)
-                .EnvironmentVariable("COREHOST_TRACE", "1")
-                .CaptureStdErr()
-                .CaptureStdOut()
+                .EnableTracingAndCaptureOutputs()
                 .Execute()
                 .Should().Pass()
                 .And.HaveStdErrContaining($"Property {sharedState.AppTestPropertyName} = {sharedState.AppTestPropertyValue}")
@@ -43,9 +41,7 @@ public void FrameworkConfigProperty_AppCanGetData()
             var dotnet = fixture.BuiltDotnet;
             var appDll = fixture.TestProject.AppDll;
             dotnet.Exec(appDll, sharedState.FrameworkTestPropertyName)
-                .EnvironmentVariable("COREHOST_TRACE", "1")
-                .CaptureStdErr()
-                .CaptureStdOut()
+                .EnableTracingAndCaptureOutputs()
                 .Execute()
                 .Should().Pass()
                 .And.HaveStdErrContaining($"Property {sharedState.FrameworkTestPropertyName} = {sharedState.FrameworkTestPropertyValue}")
@@ -65,15 +61,28 @@ public void DuplicateConfigProperty_AppConfigValueUsed()
             var dotnet = fixture.BuiltDotnet;
             var appDll = fixture.TestProject.AppDll;
             dotnet.Exec(appDll, sharedState.FrameworkTestPropertyName)
-                .EnvironmentVariable("COREHOST_TRACE", "1")
-                .CaptureStdErr()
-                .CaptureStdOut()
+                .EnableTracingAndCaptureOutputs()
                 .Execute()
                 .Should().Pass()
                 .And.HaveStdErrContaining($"Property {sharedState.FrameworkTestPropertyName} = {sharedState.AppTestPropertyValue}")
                 .And.HaveStdOutContaining($"AppContext.GetData({sharedState.FrameworkTestPropertyName}) = {sharedState.AppTestPropertyValue}");
         }
 
+        [Fact]
+        public void HostFxrPathProperty_NotVisibleFromApp()
+        {
+            var fixture = sharedState.RuntimePropertiesFixture
+                .Copy();
+
+            var dotnet = fixture.BuiltDotnet;
+            var appDll = fixture.TestProject.AppDll;
+            dotnet.Exec(appDll, sharedState.HostFxrPathPropertyName)
+                .EnableTracingAndCaptureOutputs()
+                .Execute()
+                .Should().Pass()
+                .And.HaveStdOutContaining($"Property '{sharedState.HostFxrPathPropertyName}' was not found.");
+        }
+
         [Fact]
         public void DuplicateCommonProperty_Fails()
         {
@@ -88,9 +97,7 @@ public void DuplicateCommonProperty_Fails()
             var dotnet = fixture.BuiltDotnet;
             var appDll = fixture.TestProject.AppDll;
             dotnet.Exec(appDll)
-                .EnvironmentVariable("COREHOST_TRACE", "1")
-                .CaptureStdErr()
-                .CaptureStdOut()
+                .EnableTracingAndCaptureOutputs()
                 .Execute()
                 .Should().Fail()
                 .And.HaveStdErrContaining($"Duplicate runtime property found: {name}");
@@ -105,6 +112,7 @@ public class SharedTestState : IDisposable
             public string AppTestPropertyValue => "VALUE_FROM_APP";
             public string FrameworkTestPropertyName => "FRAMEWORK_TEST_PROPERTY";
             public string FrameworkTestPropertyValue => "VALUE_FROM_FRAMEWORK";
+            public string HostFxrPathPropertyName => "HOSTFXR_PATH";
 
             private readonly string copiedDotnet;
 

src/native/corehost/hostpolicy/coreclr.cpp

@@ -149,7 +149,8 @@ namespace
         _X("RUNTIME_IDENTIFIER"),
         _X("BUNDLE_PROBE"),
         _X("HOSTPOLICY_EMBEDDED"),
-        _X("PINVOKE_OVERRIDE")
+        _X("PINVOKE_OVERRIDE"),
+        _X("HOSTFXR_PATH")
     };
 
     static_assert((sizeof(PropertyNameMapping) / sizeof(*PropertyNameMapping)) == static_cast<size_t>(common_property::Last), "Invalid property count");

src/native/corehost/hostpolicy/coreclr.h

@@ -68,6 +68,7 @@ enum class common_property
     BundleProbe,
     HostPolicyEmbedded,
     PInvokeOverride,
+    HostFxrPath,
     // Sentinel value - new values should be defined above
     Last
 };

src/native/corehost/hostpolicy/hostpolicy_context.cpp

@@ -290,6 +290,16 @@ int hostpolicy_context_t::initialize(hostpolicy_init_t &hostpolicy_init, const a
         }
     }
 
+    // We pass the loaded hostfxr path to the SDK can load it without relying on dlopen/LoadLibrary to find it.
+    if (host_mode == host_mode_t::muxer &&
+        (pal::strcmp(get_filename(application).c_str(), _X("dotnet.dll")) == 0))
+    {
+        pal::dll_t fxr;
+        pal::string_t fxr_path;
+        pal::get_loaded_library(LIBFXR_NAME, "hostfxr_main", &fxr, &fxr_path);
+        coreclr_properties.add(common_property::HostFxrPath, fxr_path.c_str());
+    }
+
 #if defined(NATIVE_LIBS_EMBEDDED)
     // PInvoke Override
     if (bundle::info_t::is_single_file_bundle())