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Backreferences to non-participating groups are handled incorrectly #26

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jaynetics opened this issue Dec 22, 2024 · 1 comment

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jaynetics commented Dec 22, 2024

Issue extracted from #21.

E.g. ruby does this:

/\1()/.match?('foo') # => false

but the resulting js regex, with the same source, produces a zero-length match on any string.

slevithan commented Dec 22, 2024 •

edited

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A few other examples of regexes that include nonparticipating capturing groups:

(\1) - should fail to match
(a)|b\1 - should never match the second alternative
(?<n>a)|(?<n>)\k<n> - the backreference should not allow matching an empty string as one of the multiplexed options (see No backref multiplexing #28)

Might include a nonparticipating capturing group:

(a)?b\1
((a)|b)+\2

Never includes a nonparticipating capturing group:

(a?)b\1

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