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I am trying to figure out how to capture the positive lookahead group in the following regex:

(((Initial commit)|(Merge [^\r\n]+)|(((build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test|BREAKING CHANGE)(\(\w+\))?!?: ([\w ]+))(\r|\n|\r\n){0,2}((?:\w|\s|\r|\n|\r\n)+)(?=(((\r|\n|\r\n){2}([\w-]+): (\w+))|$)))))

My sample dataset I am trying to match with is as follows:

#1

build(Breaking): la asdf asdf asdf

asdfasdf asdf asdf
asdf
asdf
asdf

asdf
asdf

asdf

aef asdf asdf

#2

build(Breaking): la asdf asdf asdf

asdfasdf asdf asdf
asdf
asdf
asdf

asdf
asdf

asdf

aef asdf asdf

asdf-asdf: asdf

I successfully capture all fields preceeding the positive lookahead of asdf-asdf: asdf, whether or not it is there, but for some reason, even if the positive look-ahead finds the asdf-asdf: asdf match, the capturing group doesn't seem to capture the asdf-asdf: asdf match.

What should I be doing in order to accomplish this goal, or what am I doing wrong?

cremedekhan
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  • This pattern looks heavily over-bracketed and can leave one in despair. Myself I can't see the reason for trying to capture inside a lookahead, but maybe there is one like overlapping? (match full str, but capture part str). Unclear about this. My guess is something without lookahead could suffice. See this demo: [`Initial commit|Merge [^\r\n]+|(?:(build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test|BREAKING CHANGE)(\(\w+\))?!?: ([\w ]+))(?:\r?\n){0,2}([\w\s]+)(?:\r?\n([\w-]+): (\w+)|$)`](https://regex101.com/r/Ufzun9/1) – bobble bubble Jul 14 '22 at 11:42

1 Answers1

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Your regex string is very long, but your problem is essentially that your positive lookahead is not being captured, because positive lookaheads do not capture itself. A simpler example is bad (?=tea) which will not capture bad tea and only bad . However if you do bad (?=(tea))\1 it will indeed capture the entire string. Your correct regex string is

(((Initial commit)|(Merge [^\r\n]+)|(((build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test|BREAKING CHANGE)(\(\w+\))?!?: ([\w ]+))(\r|\n|\r\n){0,2}((?:\w|\s|\r|\n|\r\n)+)(?=(((\r|\n|\r\n){2}([\w-]+): (\w+))|$))\12)))

You simply add \12 (or just replicate whatever string is inside the positive lookahead) after the lookahead itself.

Subienay Ganesh
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