SymbolResults improvements

[adamsitnik]

SymbolResults improvements based on feedback from our last meeting (notes):

• single, readonly LocalizationResources for entire symbol tree
• removed Symbol from SymbolResult, as each derived type defines a more specific property (OptionResult.Option etc)
• moved SymbolResult.Children to Command.Children, as it's the only type that officially has them (the fact that Option has them is an implementation detail)
• removed a lot of allocations by not storing a list of children per symbol/command and re-using the information present in symbol dictionary (we just search for instances with Parent equal to given symbol result)

I still need to implement a copy-free approach for Symbol.Tokens and I don't like the fact that many of the SymbolResults properties/methods are virtual and just calling Root.MethodAbc. I'll send another PR tomorrow or just update this one.

[adamsitnik]

previously this logic was performed as part of the validation (ValidateAndConvertOptionResult). Since here we know that given OptionNode was parsed with no arguments, we can create the argument result now and let validation method just validate without performing mutations.

command-line-api/src/System.CommandLine/Parsing/ParseResultVisitor.cs

Lines 489 to 500 in 9c48247

	if (optionResult.Children.Count == 0)
	{
	if (optionResult.Option.Argument is { HasCustomParser: true })
	{
	if (optionResult.Option is { } opt)
	{
	var argResult = optionResult.GetOrCreateDefaultArgumentResult(opt.Argument);
	optionResult.AddChild(argResult);
	ValidateAndConvertArgumentResult(argResult);
	}
	}
	}

[adamsitnik]

this is guaranteed to work, there can be no parsed OptionArgumentNode without option being parsed and handled first

[jonsequitur]

I think you can use BeOfType here, no?

[adamsitnik]

iirc it's RootCommandResult here (which is internal)

edit:

[xUnit.net 00:00:00.93]     System.CommandLine.Tests.ArgumentTests+CustomParsing.Command_ArgumentResult_Parent_is_set_correctly_when_token_is_implicit [FAIL]
  Failed System.CommandLine.Tests.ArgumentTests+CustomParsing.Command_ArgumentResult_Parent_is_set_correctly_when_token_is_implicit [34 ms]
  Error Message:
   Expected type to be System.CommandLine.Parsing.CommandResult, but found System.CommandLine.Parsing.RootCommandResult.
  Stack Trace:
     at FluentAssertions.Execution.XUnit2TestFramework.Throw(String message)
   at FluentAssertions.Execution.TestFrameworkProvider.Throw(String message)
   at FluentAssertions.Execution.DefaultAssertionStrategy.HandleFailure(String message)
   at FluentAssertions.Execution.AssertionScope.FailWith(Func`1 failReasonFunc)
   at FluentAssertions.Execution.AssertionScope.FailWith(Func`1 failReasonFunc)
   at FluentAssertions.Execution.AssertionScope.FailWith(String message, Object[] args)
   at FluentAssertions.Types.TypeAssertions.Be(Type expected, String because, Object[] becauseArgs)
   at FluentAssertions.Primitives.ReferenceTypeAssertions`2.BeOfType(Type expectedType, String because, Object[] becauseArgs)
   at FluentAssertions.Primitives.ReferenceTypeAssertions`2.BeOfType[T](String because, Object[] becauseArgs)
   at System.CommandLine.Tests.ArgumentTests.CustomParsing.Command_ArgumentResult_Parent_is_set_correctly_when_token_is_implicit() in D:\projects\command-line-api\src\System.CommandLine.Tests\ArgumentTests.cs:line 340
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)

[adamsitnik]

@jonsequitur thank you for the review!