Macros do not persist despite gdef and globalGroup

[recmo]

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• Check the bug is reproducible in the demo. If not, check KaTeX is up-to-date and installed correctly.
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Describe the bug:
Macros are forgotten between invocations of renderToString (and possibly render), even when globalGroup is set and \gdef is used.

katex.renderToString(String.raw`\gdef\foo{1}`);
katex.renderToString(String.raw`\foo`); // Fails

katex.renderToString(String.raw`\gdef\foo{1}`, { globalGroup: true });
katex.renderToString(String.raw`\foo`); // Fails

To Reproduce:
Steps to reproduce the behavior:

1. Go to 'https://katex.org.'
2. Open javascript console
3. Enter either of the two examples above
4. See error Uncaught ParseError: KaTeX parse error: Undefined control sequence: \foo at position 1: \̲f̲o̲o̲

Expected behavior:
Foo macro to expand because it was defined globally.

Screenshots:
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• KaTeX Version: 0.12.0
• Device: Desktop
• OS: MacOS 10.15.6 (19G2021)
• Browser: Firefox
• Version: 80.0.1 (64-bit)

Additional context:
I'm trying to define some globally available macros that require arguments. Doing this through the macros option seems extremely complicated and I can not find a working example, I'd much prefer parsing some \gdef statements. Unfortunately this does not work either.

[recmo]

After digging some more, the following seems to work:

var macros = {};
katex.renderToString(String.raw`\gdef\foo{1}`, { macros });
katex.renderToString(String.raw`\foo`, { macros })

This solves it for me, but it took me many hours to figure out.

[edemaine]

Right, that's the intended behavior -- sorry it took you hours to figure out! Do you have a suggestion on where we (or you via PR) could mention this in the documentation that would have helped you find it sooner?