Fix unknown command throws System.InvalidOperationException: Enumeration already finished (#542)

* Update tests to run .NET 8
* Don't call enumerator.Current if MoveNext is not called or returns false in CommandArgumentEnumerator.

---------

Co-authored-by: Adam Sällergård <[email protected]>

Author: sallerga

src/CommandLineUtils/Internal/CommandLineProcessor.cs

@@ -519,10 +519,12 @@ public void Dispose()
         private sealed class CommandArgumentEnumerator : IEnumerator<CommandArgument>
         {
             private readonly IEnumerator<CommandArgument> _enumerator;
+            private bool _currentValid;
 
             public CommandArgumentEnumerator(IEnumerator<CommandArgument> enumerator)
             {
                 _enumerator = enumerator;
+                _currentValid = false;
             }
 
             public CommandArgument Current => _enumerator.Current;
@@ -533,9 +535,10 @@ public CommandArgumentEnumerator(IEnumerator<CommandArgument> enumerator)
 
             public bool MoveNext()
             {
-                if (Current == null || !Current.MultipleValues)
+                if (!_currentValid || !Current.MultipleValues)
                 {
-                    return _enumerator.MoveNext();
+                    _currentValid = _enumerator.MoveNext();
+                    return _currentValid;
                 }
 
                 // If current argument allows multiple values, we don't move forward and

test/CommandLineUtils.Tests/McMaster.Extensions.CommandLineUtils.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net7.0;net6.0</TargetFrameworks>
+    <TargetFrameworks>net8.0;net7.0;net6.0</TargetFrameworks>
     <TargetFrameworks Condition="'$(TestFullFramework)' != 'false'">$(TargetFrameworks);net472</TargetFrameworks>
     <!-- Once xunit supports nullable reference types, I might reconsider -->
     <Nullable>annotations</Nullable>

test/Hosting.CommandLine.Tests/McMaster.Extensions.Hosting.CommandLine.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net7.0;net6.0</TargetFrameworks>
+    <TargetFrameworks>net8.0;net7.0;net6.0</TargetFrameworks>
     <TargetFrameworks Condition="'$(TestFullFramework)' != 'false'">$(TargetFrameworks);net472</TargetFrameworks>
   </PropertyGroup>