globalGroup adversely affects \color and tall right delimiters

PR #2091 has an unintended consequence. When the rendering option globalGroup is set to true, then \color escapes its group and affects tall right delimiters.

The KaTeX function\color works by creating a macro \current@color and assigning a color to it. When globalGroup is true, then this macro escapes its group. Tall right delimiters are then given that color in line https://github.com/KaTeX/KaTeX/blob/21c4bc355c04cfa13bb79dd9dd06627f5b04f54d/src/functions/delimsizing.js#L155. I don’t know why tall right delimiters get that treatment, but there it is.

The stated reason for PR #2091 was to give global scope to \newcommand. But its effect is more sweeping than that. I think that @edemaine’s comment was correct. We need some mechanism that gives global scope to \newcommand, not to all macros.

[ronkok]

Note that this will only be an issue for \color at the top level.

It will actually be an issue for any top level \def, not just color. You probably already realize that, but I want it clearly stated.

Please cast an eye over PR #2640. It’s intent is to restore local scope to any \def, regardless of KaTeX settings. \newcommand can still persist between calls to KaTeX, which accomplishes the original goal for globalScope.

[ronkok]

I’ll mention one other thing. I think it is valuable to maintain a distinction between \def and \gdef regardless of what happens to right delimiters. \def should not be global.