Updating HelpBuilder.WriteColumns to be easier to extend

[Keboo]

While updating ClangSharp to the latest System.CommandLine I ran into the issue of a custom HelpBuilder wanting to leverage the two column layout for some arbitrary items. This required building a HelpContext despite the method only needing a TextWriter to output to.

See: dotnet/ClangSharp#343

[jonsequitur]

I wonder if another helper method like this work:

command-line-api/src/System.CommandLine/Help/HelpBuilderExtensions.cs

Lines 31 to 40 in 74ae46e

	/// <summary>
	/// Writes help output for the specified command.
	/// </summary>
	public static void Write(
	this HelpBuilder helpBuilder,
	Command command,
	TextWriter writer)
	{
	helpBuilder.Write(new HelpContext(helpBuilder, command, writer));
	}

HelpBuilder.Write also takes a HelpContext and keeping things consistent on this type leaves an opening to add things to the HelpContext later.

[Keboo]

The only issue with that type of extension is it makes is very difficult for anyone to use the built-in two column layout with arbitrary content. For the PR linked above, there is a large bit of content simply wants to be written out using the two-column layout. To work around the API I did something similar, the suggested extension method still assumes that the input to the function will come from a command. Where in this case what is desired is a way for an option to give "help-like" behavior with a lot of additional details. Really that code path doesn't really need to even go through a help builder, it is only using it to get some of the formatting niceness, but the input is "custom".

[jonsequitur]

I wonder if that suggests that the problem isn't so much the HelpContext as the fact that it's so Command-centric.

[Keboo]

I think that is a good summary. Which brings up two questions. 1. Should it be less command centric? 2. Any thoughts on what that should like?

[jonsequitur]

One approach off the top of my head could be to change HelpBuilder.Write to accept Symbol and change HelpContext.Command to HelpContext.Symbol. That might have a bit of a ripple effect, though.