⚡✅ Update more regexps to run in linear time #147
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The BIDI_FAILURE regexps all used `\g<name>` to define char classes and then re-use them. Unfortunately, ruby 3.2 can't compile that to run in linear time. The regexps could also be written using lookahead, but that also wouldn't run in linear time. The debug output gsub is simple to accomplish without negative lookahead by using a block with gsub and checking `$'.empty?`. `bin/check-regexps` was added for quick double-check, just in case the tests aren't catching everything.
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I didn't have time to look closely at these when I pushed #145. For that PR, I prioritized
BEG_REGEXPbecause it is used all the time, with unconstrained input. These other regexps are only used whenNet::IMAP.debug = truthyor bysaslprep, which is only used by the SCRAM-SHA-256 SASL mechanism, which isn't even merged yet, oops! (See #54, #78)So this fixes both of those.
For the debug output gsub, the same string transform is simple to accomplish without negative lookahead by using a block with gsub and checking
$'.empty?. I don't believeNet::IMAP.debughas any tests, but 1) I did test it manually, and 2) I intend to push a PR that changes how strings are validated, generated, and sent. The updated output will also change (simplify) this debug output, allowing redaction of passwords and authentication tokens, and come with its own tests.For
StringPrep::SASLprep::BIDI_FAILUREand the other related regexps, they all used\g<name>to define char classes and then re-use them. Unfortunately, ruby 3.2 can't compile\g<...>to run in linear time. The regexps can also be shortened by using lookahead, but that also can't run in linear time. Although this expands theBIDI_FAILUREregexp to ~15Kb, it slightly simplifies the generation.