匹配注释，除非起始字符被未转义的引号包围

Question

With a regex: How can I match comments which begin with a semicolon unless the semicolon is surrounded on both sides by unescaped quotes, as shown below (the green blocks denote the matched comments )?:

Note, that the dquotes can by escaped by doubling them up "" . Such escaped dquotes behave as completely different characters, ie they do not have the ability to surround the semicolon and disable its comment-starting function.

Also, unbalanced dquotes are treated as escaped dquotes.

With Bubble's help, I have gotten as far as the regex below, which fails to correctly treat a trailing escaped dquote in the last test vector line.

^(?>(?:""[^""\n]*""|[^;""\n]+)*)""?[^"";\n]*(;.*)

See it run here .

Test vectors (the same as in the color-coded diagram above):

Peekaboo ; A comment starts with a semicolon and continues till the EOL
Unless the semicolon is surrounded by dquotes ”Don’t do it ; here” ;but match me; once
Im not surrounded ”so pay attention to me” ; ”peekaboo”
Im not surrounded ”so pay attention” to;me” ; ”peekaboo”
Im not surrounded ”so pay attention to me ; peekaboo
Dquote escapes a dquote so ”dont pay attention to ””me;here”” buster” do it ; here
Don’t pay attention to  ”””me;here””” but do ””it;here””
and ”dont do ””it;here”””  either ;peekaboo
but "pay attention to "it;here"" ;not here though
Simon said ”I like goats” then he added ”and sheep;” ;a good comment is ”here
Simon said ”I like goats” then he added ”and sheep;” dont do it here
Simon said ””I like goats;”peekaboo
Simon said ”I like goats;””peekaboo

Answer 1

The task is to find comments starting with a ; semicolon outside quotes considering "" escaped quotes and a potential non-closed quote before. This approach works for yet provided test cases.

Updated pattern : A shorter and more efficient variant without alternation .

^((?>(?:(?:[^"\n;]*"[^"\n]*")+(?!"))?[^"\n;]*)"?[^"\n;]*);.*

New demo at regex101

This pattern works without alternation and uses a negative lookahead to check for the last valid double quote. In both patterns the atomic group mimics possessive quantifiers to prevent any backtracking and keep the balance. Using possessive quantifiers the pattern would look like this regex101 demo . [^";\n]*"?[^";\n]* is the part that is allowing an optional non-closed quote.

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Previous pattern : This turned out to be reliable yet but is a little bit slower.

^((?>(?:(?:[^;"\n]*"(?>(?:[^"\n]+|"")*)")+)?)[^";\n]*"?[^";\n]*);.*

Old demo at regex101

"(([^"]+|"")*)" consumes either " ... " or "" . This gets repeated any amount of times with any [^;"]* characters that are not ; or " in between. All that is done inside an atomic group . Having matched the quoted parts with any non semicolons in between due to use of an atomic group there is no way back. After finally allowing an optional non-closed " either a ; will be found or it fails.

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The first capturing group $1 contains the part up to the targeted ; comment-start . To remove the comment, replace the full match with the captured part. If needed capture (.*) to a second group .

regex-part	matches
(?> ... )	denotes an atomic group , used to prevent any further backtracking
[^ ... ]	a negated character class matches a single character not in the listed
( ... ) and (?: ... )	capturing and non capturing groups (latter for repitition or alternation )
quantifiers : ? * +	? matches zero or one ( optional ), * any amount and + one or more

If replacements are done on single lines, all the \n newlines can be dropped from either pattern.