Allow a selection of text to be parsed in the playground

[NickLarsenNZ]

Currently the whole text is parsed, which means when debugging single rules, you have to keep deleting and re-adding sections of the input text.

It would be really nice to be able to select lines to parse, so that the text input can stay relatively static while you work on the grammar rules.

It would be super cool if it worked the same as Github selections (where you can click a line number, hold SHIFT, then click another line number - and the URL also has a selection fragment like #L7-L15).

[tomtau]

@LeoDog896 @nathanielknight any thoughts?

[tristan-f-r]

CodeMirror doesn't have any explicit plugins for gutter-based line selection, I believe, so there would have to be a home-baked solution. Optionally, it could be based on the selected text in the editor, but that would be much more finicky. I would put the gutter selection inside the share string, though, instead of its own separate hash.

tl;dr the base feature sounds good 👍

[nathanielknight]

I like the idea, but I agree that the implementation would be tricky. It might be easier to replace the editor with a stack of editors and let you break up your text that way instead?