Regexp caching

[apalala]

Caching by re.compile() is mostly undocumented and unreliable.

Implement caching of compiled regexes for the few critical ones in TatSu configurations.

[vfazio]

I don't know if you want to address it in this MR, but I do want to call out that we're still applying (?m) implicitly on whitespace:

TatSu/tatsu/buffering.py

Line 96 in 0240667

return re.compile(f'(?m){whitespace}')

You've updated the ebnf grammar to specify this flag explicitly

TatSu/grammar/tatsu.ebnf

Line 2 in 0240667

@@whitespace :: /(?m)\s+/

which was necessary when it was an re.Pattern but the parsing will be hitting the str branch of this logic. It may make sense to just remove that (?m) and update the documentation to say users need to update their patterns as necessary.

[vfazio]

seems ok so far, just a question on the whitespace pattern which could be spun off into a new issue/PR and the regex validation

[apalala]

seems ok so far, just a question on the whitespace pattern which could be spun off into a new issue/PR and the regex validation

Yes! There may be more improvements in further issues and pull requests.

I'd like to merge and make a release now to get feedback about what projects we broke ASAP.

[vfazio]

Last minor fixup. Since you're updating whitespace I think it would be nice to add a note to the documentation like was done for the comments and eol_comments:

TatSu/docs/directives.rst

Lines 121 to 127 in f3fb92a

	@@whitespace :: /[\t ]+/
	To disable any parsing of whitespace, use ``None`` for the definition:
	.. code::
	@@whitespace :: None

Should be OK after this minor change

[vfazio]

@apalala do you want me to merge this or do you want to?