Allow launching file-based apps via dnx

documentation/general/dotnet-run-file.md

@@ -120,6 +120,35 @@ and it is not a DLL path, built-in command, or a NuGet tool (e.g., `dotnet watch
 even if a valid `watch` file-based app exists in the current directory;
 one can use `dotnet ./watch` to run the file-based app).
 
+### `dnx`
+
+The `dnx` launcher also supports running file-based apps whose target path is valid according to the same rules as `dotnet run`:
+the file must exist and either have a `.cs` extension or start with `#!`.
+The target path must also be explicit: it must be fully qualified or contain a directory separator,
+such as `./app`, `../app`, or `some/directory/app`.
+This requirement avoids ambiguity with NuGet tool package IDs, so a bare `dnx app` always retains the existing tool execution behavior
+even if a file named `app` exists in the current directory.
+
+```ps1
+dnx ./some/path.cs arg0 arg1
+```
+
+This is equivalent to `dotnet run --file ./some/path.cs -- arg0 arg1`.
+All arguments after the target path are passed to the app verbatim, including a literal `--`
+and arguments that have the same names as `dnx` tool options.
+
+For file-based apps, `dnx` starts the `dotnet` host with the target directory as its working directory so SDK resolution,
+including the search for `global.json`, starts from the target directory rather than the directory from which `dnx` was invoked.
+After the SDK CLI has started, `dnx` restores the original working directory before building and running the app.
+Consequently, implicit build files such as `Directory.Build.props` are still discovered relative to the file-based app,
+while the running app observes the directory from which the user invoked `dnx` as its current working directory.
+
+For example, `cd /x/ && dnx /y/file.cs` searches for `global.json` and implicit build files from `/y/`,
+but runs the app with `/x/` as its current working directory.
+
+If the first argument is not a valid file-based app target path, `dnx` retains its existing NuGet tool execution behavior:
+it uses the newest installed SDK regardless of `global.json`.
+
 ### Other commands
 
 Commands `dotnet restore file.cs` and `dotnet build file.cs` are needed for IDE support and hence work for file-based programs.

src/Cli/Microsoft.DotNet.Cli.Definitions/CommandDefinitionStrings.resx

@@ -1057,9 +1057,15 @@ The default is to publish a framework-dependent application.</value>
   <data name="RunFrameworkOptionDescription" xml:space="preserve">
     <value>The target framework to run for. The target framework must also be specified in the project file.</value>
   </data>
+  <data name="RunFileModeOptionDescription" xml:space="preserve">
+    <value>Treat the first application argument as the file-based app to run. A relative file path is resolved against the directory specified by --working-directory.</value>
+  </data>
   <data name="RunRuntimeOptionDescription" xml:space="preserve">
     <value>The target runtime to run for.</value>
   </data>
+  <data name="RunWorkingDirectoryOptionDescription" xml:space="preserve">
+    <value>The working directory to use when running the application. This option overrides the working directory from a launch profile.</value>
+  </data>
   <data name="SdkAppFullName" xml:space="preserve">
     <value>.NET SDK Command</value>
   </data>
@@ -1551,4 +1557,16 @@ If command is specified without the argument, it lists all the template packages
   <data name="SDKSchemaCommandDefinition" xml:space="preserve">
     <value>Display the command schema as JSON.</value>
   </data>
+  <data name="DnxCommandDescription" xml:space="preserve">
+    <value>Run a file-based app or execute a tool package without permanently installing it.</value>
+  </data>
+  <data name="DnxPackageOrFileArgumentDescription" xml:space="preserve">
+    <value>A qualified path to a file-based app, or a package reference in the form of a package identifier like 'dotnetsay' or package identifier and version separated by '@' like 'dotnetsay@2.1.7'.</value>
+  </data>
+  <data name="DnxPackageOrFileArgumentName" xml:space="preserve">
+    <value>FILE_OR_PACKAGE</value>
+  </data>
+  <data name="DnxArgumentsDescription" xml:space="preserve">
+    <value>Arguments forwarded to the file-based app or tool.</value>
+  </data>
 </root>

src/Cli/Microsoft.DotNet.Cli.Definitions/Commands/Dnx/DnxCommandDefinition.cs

@@ -8,8 +8,12 @@ namespace Microsoft.DotNet.Cli.Commands.Dnx;
 internal sealed class DnxCommandDefinition : ToolExecuteCommandDefinitionBase
 {
     public DnxCommandDefinition()
-        : base("dnx")
+        : base("dnx", CommandDefinitionStrings.DnxPackageOrFileArgumentName)
     {
+        Description = CommandDefinitionStrings.DnxCommandDescription;
+        PackageIdentityArgument.Description = CommandDefinitionStrings.DnxPackageOrFileArgumentDescription;
+        PackageIdentityArgument.HelpName = CommandDefinitionStrings.DnxPackageOrFileArgumentName;
+        CommandArgument.Description = CommandDefinitionStrings.DnxArgumentsDescription;
         Hidden = true;
     }
 }

src/Cli/Microsoft.DotNet.Cli.Definitions/Commands/Run/RunCommandDefinition.cs

@@ -29,6 +29,17 @@ internal sealed class RunCommandDefinition : Command
         HelpName = CommandDefinitionStrings.CommandOptionFileHelpName,
     };
 
+    public readonly Option<bool> FileModeOption = new("--file-mode")
+    {
+        Description = CommandDefinitionStrings.RunFileModeOptionDescription,
+        Hidden = true,
+    };
+
+    public readonly Option<string> WorkingDirectoryOption = new("--working-directory")
+    {
+        Description = CommandDefinitionStrings.RunWorkingDirectoryOptionDescription,
+    };
+
     public readonly Option<ReadOnlyDictionary<string, string>?> PropertyOption = CommonOptions.CreatePropertyOption();
 
     public readonly Option<string> LaunchProfileOption = new("--launch-profile", "-lp")
@@ -107,6 +118,8 @@ public RunCommandDefinition()
         Options.Add(FrameworkOption);
         Options.Add(ProjectOption);
         Options.Add(FileOption);
+        Options.Add(FileModeOption);
+        Options.Add(WorkingDirectoryOption);
         Options.Add(PropertyOption);
         Options.Add(LaunchProfileOption);
         Options.Add(NoLaunchProfileOption);

src/Cli/Microsoft.DotNet.Cli.Definitions/Commands/Tool/ToolExecuteCommandDefinition.cs

@@ -16,7 +16,7 @@ public ToolExecuteCommandDefinition()
 
 internal abstract class ToolExecuteCommandDefinitionBase : Command
 {
-    public readonly Argument<PackageIdentityWithRange> PackageIdentityArgument = CommonArguments.CreateRequiredPackageIdentityArgument("dotnetsay", "2.1.7");
+    public readonly Argument<PackageIdentityWithRange> PackageIdentityArgument;
 
     public readonly Argument<IEnumerable<string>> CommandArgument = new("commandArguments")
     {
@@ -34,9 +34,13 @@ internal abstract class ToolExecuteCommandDefinitionBase : Command
 
     public readonly NuGetRestoreOptions RestoreOptions = new(forward: true);
 
-    public ToolExecuteCommandDefinitionBase(string name)
+    public ToolExecuteCommandDefinitionBase(string name, string packageIdentityArgumentName = CommonArguments.PackageIdArgumentName)
         : base(name, CommandDefinitionStrings.ToolExecuteCommandDescription)
     {
+        PackageIdentityArgument = CommonArguments.CreateRequiredPackageIdentityArgument(
+            "dotnetsay",
+            "2.1.7",
+            packageIdentityArgumentName);
         Arguments.Add(PackageIdentityArgument);
         Arguments.Add(CommandArgument);
 

src/Cli/Microsoft.DotNet.Cli.Definitions/Common/CommonArguments.cs

@@ -22,8 +22,11 @@ internal static class CommonArguments
                 IsDynamic = true
             };
 
-        public static Argument<PackageIdentityWithRange> CreateRequiredPackageIdentityArgument(string examplePackage = "Newtonsoft.Json", string exampleVersion = "13.0.3") =>
-            new(PackageIdArgumentName)
+        public static Argument<PackageIdentityWithRange> CreateRequiredPackageIdentityArgument(
+            string examplePackage = "Newtonsoft.Json",
+            string exampleVersion = "13.0.3",
+            string argumentName = PackageIdArgumentName) =>
+            new(argumentName)
             {
                 Description = string.Format(CommandDefinitionStrings.PackageIdentityArgumentDescription, examplePackage, exampleVersion),
                 CustomParser = argumentResult => ParsePackageIdentityWithVersionSeparator(argumentResult.Tokens[0]?.Value)!.Value,