Fix Environment.GetCommandLineArgs()[0] to report the host invocation name

docs/design/features/host-runtime-information.md

@@ -40,6 +40,10 @@ Directory containing the application. This is used for [`AppContext.BaseDirector
 
 [Runtime identifier](https://learn.microsoft.com/dotnet/core/rid-catalog) for the application. This is used for [`RuntimeInformation.RuntimeIdentifier`](https://learn.microsoft.com/dotnet/api/system.runtime.interopservices.runtimeinformation.runtimeidentifier).
 
+`ARGV0`
+
+The name used to invoke an application host, corresponding to the native process's `argv[0]`. The apphost provides this property for the first element returned by [`Environment.GetCommandLineArgs()`](https://learn.microsoft.com/dotnet/api/system.environment.getcommandlineargs). Muxer-style hosts, including `dotnet` and `corerun`, do not provide this property, preserving the managed application path as the first element.
+
 ### Deps files
 
 `APP_CONTEXT_DEPS_FILES`

src/coreclr/vm/corhost.cpp

@@ -37,6 +37,7 @@
 #endif // !TARGET_UNIX
 
 #include "nativelibrary.h"
+#include "hostinformation.h"
 
 #ifndef DACCESS_COMPILE
 
@@ -217,17 +218,11 @@ HRESULT CorHost2::ExecuteApplication(LPCWSTR   pwzAppFullName,
 }
 
 /*
- * This method processes the arguments sent to the host which are then used
- * to invoke the main method.
- * Note -
- * [0] - points to the assemblyName that has been sent by the host.
- * The rest are the arguments sent to the assembly.
- * Also note, this might not always return the exact same identity as the cmdLine
- * used to invoke the method.
- *
- * For example :-
- * ActualCmdLine - Foo arg1 arg2.
- * (Host1)       - Full_path_to_Foo arg1 arg2
+ * This method constructs the array returned by Environment.GetCommandLineArgs().
+ * The first element is passed separately from argv as exePath and uses the native
+ * invocation name when provided by the host. Otherwise, the assembly or bundle path
+ * is used. The remaining elements come from argv, which contains the arguments to the
+ * main method.
 */
 static PTRARRAYREF SetCommandLineArgs(PCWSTR pwzAssemblyPath, int argc, PCWSTR* argv)
 {
@@ -242,7 +237,10 @@ static PTRARRAYREF SetCommandLineArgs(PCWSTR pwzAssemblyPath, int argc, PCWSTR*
     // Record the command line.
     SaveManagedCommandLine(pwzAssemblyPath, argc, argv);
 
-    PCWSTR exePath = Bundle::AppIsBundle() ? static_cast<PCWSTR>(Bundle::AppBundle->Path()) : pwzAssemblyPath;
+    StackSString invocationName;
+    PCWSTR exePath = HostInformation::GetProperty(HOST_PROPERTY_ARGV0, invocationName)
+        ? invocationName.GetUnicode()
+        : (Bundle::AppIsBundle() ? static_cast<PCWSTR>(Bundle::AppBundle->Path()) : pwzAssemblyPath);
 
     PTRARRAYREF result = NULL;
     GCPROTECT_BEGIN(result);

src/installer/tests/Assets/Projects/HelloWorld/Program.cs

@@ -52,6 +52,13 @@ public static void Main(string[] args)
                         Console.WriteLine($"AppContext.GetData({propertyName}) = {propertyValue}");
                     }
                     break;
+                case "print_command_line_args":
+                    string[] commandLineArgs = Environment.GetCommandLineArgs();
+                    for (int i = 0; i < commandLineArgs.Length; i++)
+                    {
+                        Console.WriteLine($"Environment.GetCommandLineArgs()[{i}] = {commandLineArgs[i]}");
+                    }
+                    break;
                 case "throw_exception":
                     // Disable core dumps - test is intentionally crashing
                     Utilities.CoreDump.Disable();

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

@@ -29,19 +29,23 @@ public void Muxer_Default()
             var dotnet = HostTestContext.BuiltDotNet;
             var appDll = sharedTestState.App.AppDll;
 
-            dotnet.Exec(appDll)
+            dotnet.Exec(appDll, "print_command_line_args")
                 .CaptureStdErr()
                 .CaptureStdOut()
                 .Execute()
                 .Should().Pass()
-                .And.HaveStdOutContaining("Hello World");
+                .And.HaveStdOutContaining("Hello World")
+                .And.HaveStdOutContaining($"Environment.GetCommandLineArgs()[0] = {appDll}")
+                .And.HaveStdOutContaining("Environment.GetCommandLineArgs()[1] = print_command_line_args");
 
-            dotnet.Exec("exec", appDll)
+            dotnet.Exec("exec", appDll, "print_command_line_args")
                 .CaptureStdErr()
                 .CaptureStdOut()
                 .Execute()
                 .Should().Pass()
-                .And.HaveStdOutContaining("Hello World");
+                .And.HaveStdOutContaining("Hello World")
+                .And.HaveStdOutContaining($"Environment.GetCommandLineArgs()[0] = {appDll}")
+                .And.HaveStdOutContaining("Environment.GetCommandLineArgs()[1] = print_command_line_args");
         }
 
         [Fact]

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

@@ -43,7 +43,8 @@ public void Symlink_all_files_fx(string symlinkRelativePath)
                     symlinks.Add(new SymLink(symlinkPath, file));
                 }
 
-                var result = Command.Create(Path.Combine(testDir.Location, symlinkRelativePath, Path.GetFileName(sharedTestState.FrameworkDependentApp.AppExe)))
+                string appHostPath = Path.Combine(testDir.Location, symlinkRelativePath, Path.GetFileName(sharedTestState.FrameworkDependentApp.AppExe));
+                var result = Command.Create(appHostPath, "print_command_line_args")
                     .CaptureStdErr()
                     .CaptureStdOut()
                     .DotNetRoot(HostTestContext.BuiltDotNet.BinPath)
@@ -54,7 +55,9 @@ public void Symlink_all_files_fx(string symlinkRelativePath)
                 // * Unix: The apphost will look next to the resolved apphost for the app dll and find the real thing
                 result
                     .Should().Pass()
-                    .And.HaveStdOutContaining("Hello World");
+                    .And.HaveStdOutContaining("Hello World")
+                    .And.HaveStdOutContaining($"Environment.GetCommandLineArgs()[0] = {appHostPath}")
+                    .And.HaveStdOutContaining("Environment.GetCommandLineArgs()[1] = print_command_line_args");
             }
             finally
             {

src/native/corehost/host_runtime_contract.h

@@ -19,6 +19,7 @@
 #define HOST_PROPERTY_BUNDLE_PROBE "BUNDLE_PROBE"
 #define HOST_PROPERTY_BUNDLE_EXTRACTION_PATH "BUNDLE_EXTRACTION_PATH"
 #define HOST_PROPERTY_ENTRY_ASSEMBLY_NAME "ENTRY_ASSEMBLY_NAME"
+#define HOST_PROPERTY_ARGV0 "ARGV0"
 #define HOST_PROPERTY_NATIVE_DLL_SEARCH_DIRECTORIES "NATIVE_DLL_SEARCH_DIRECTORIES"
 #define HOST_PROPERTY_PINVOKE_OVERRIDE "PINVOKE_OVERRIDE"
 #define HOST_PROPERTY_PLATFORM_RESOURCE_ROOTS "PLATFORM_RESOURCE_ROOTS"

src/native/corehost/hostpolicy/args.cpp

@@ -23,6 +23,9 @@ bool parse_arguments(
     pal::string_t managed_application_path;
     if (init.host_mode == host_mode_t::apphost)
     {
+        assert(argc > 0 && argv != nullptr);
+        args.invocation_name = argv[0];
+
         // Find the managed app in the same directory
         managed_application_path = init.host_info.app_path;
 

src/native/corehost/hostpolicy/args.h

@@ -126,6 +126,7 @@ struct arguments_t
     host_mode_t host_mode;
     pal::string_t app_root;
     pal::string_t deps_path;
+    pal::string_t invocation_name;
     pal::string_t managed_application;
 
     int app_argc;

src/native/corehost/hostpolicy/hostpolicy_context.cpp

@@ -122,6 +122,14 @@ namespace
             return pal::pal_utf8string(get_filename_without_ext(context->application), value_buffer, value_buffer_size);
         }
 
+        if (::strcmp(key, HOST_PROPERTY_ARGV0) == 0)
+        {
+            if (context->invocation_name.empty())
+                return -1;
+
+            return pal::pal_utf8string(context->invocation_name, value_buffer, value_buffer_size);
+        }
+
         if (::strcmp(key, HOST_PROPERTY_BUNDLE_EXTRACTION_PATH) == 0)
         {
             if (!bundle::info_t::is_single_file_bundle())
@@ -167,6 +175,7 @@ int hostpolicy_context_t::initialize(const hostpolicy_init_t &hostpolicy_init, c
     application = args.managed_application;
     host_mode = hostpolicy_init.host_mode;
     host_path = hostpolicy_init.host_info.host_path;
+    invocation_name = args.invocation_name;
     breadcrumbs_enabled = enable_breadcrumbs;
 
     deps_json_t::rid_resolution_options_t rid_resolution_options

src/native/corehost/hostpolicy/hostpolicy_context.h

@@ -20,6 +20,7 @@ struct hostpolicy_context_t
     pal::string_t clr_path;
     host_mode_t host_mode;
     pal::string_t host_path;
+    pal::string_t invocation_name;
 
     bool breadcrumbs_enabled;
     mutable std::unordered_set<pal::string_t> breadcrumbs;