How to exclude occurrences after a positive lookbehind?

Question

Suppose I have the following markdown list items:

- [x] Example of a completed task.
- [x] ! Example of a completed task.
- [x] ? Example of a completed task.

I am interested to parse that item using regex and extract the following group captures:

• $1: the left [ and the right ] brackets when the symbol x is in-between
• $2: the symbol x in between the brackets [ and ]
• $3: the modifier ! that follows after [x]
• $4: the modifier ? that follows after [x]
• $5: the text that follows [x] without a modifier, e.g., [x] This is targeted.
• $6: the text that follows [x] !
• $7: the text that follows [x] ?

After a lot of trial-and-error using online parsers, I came up with the following:

((?<=x)\]|\[(?=x]))|((?<=\[)x(?=\]))|((?<=\[x\]\s)!(?=\s))|((?<=\[x\]\s)\?(?=\s))|((?<=\[x\]\s)[^!?].*)|((?<=\[x\]\s!\s).*)|((?<=\[x\]\s\?\s).*)

To make the regex above more readable, these are the capture groups listed one by one:

• $1: ((?<=x)\]|\[(?=x]))
• $2: ((?<=\[)x(?=\]))
• $3: ((?<=\[x\]\s)!(?=\s))
• $4: ((?<=\[x\]\s)\?(?=\s))
• $5: ((?<=\[x\]\s)[^!?].*)
• $6: ((?<=\[x\]\s!\s).*)
• $7: ((?<=\[x\]\s\?\s).*)

This is most likely not the best way to do it, but at least it seems to capture what I want:

I would like to extend that regex to capture lines in a markdown table that looks like this:

|       | Task name                               |    Plan     |   Actual    |      File      |
| :---- | :-------------------------------------- | :---------: | :---------: | :------------: |
| [x]   | Task one with a reasonably long name.   | 08:00-08:45 | 08:00-09:00 |  [[task-one]]  |
| [x] ! | Task two with a reasonably long name.   | 09:00-09:30 |             |  [[task-two]]  |
| [x] ? | Task three with a reasonably long name. | 11:00-13:00 |             | [[task-three]] |

More specifically, I am interested in having the same group captures as above, but I would like to exclude the table grid (i.e., the |). So, groups $1 to $4 should stay the same, but groups $5 to $7 should capture the text, excluding the |, e.g., like in the selection below:

Do you have any ideas on how I can adjust, for example, the regex for group $5 to exclude the |. I have endlessly tried all sorts of negations (e.g., [^\|]). I am using Oniguruma regular expressions.

Answer 1

You can use

((?<=x)]|\[(?=x]))|((?<=\[)x(?=]))|((?<=\[x]\s)!(?=\s))|(?<=\[x]\s)(\?)(?=\s)|(?:\G(?!\A)\||(?<=\[x]\s[?!\s]\s\|))\K([^|\n]*)(?=\|)

See the regex101 PCRE and a Ruby (Onigmo/Oniguruma) demos.

What is added? The (?:\G(?!\A)\||(?<=\[x]\s[?!\s]\s\|))\K([^|\n]*)(?=\|) part:

• (?: - start of a non-capturing group (a custom boundary here, we'll match...)
  • \G(?!\A)\| - either the end of the previous match and a | char (i.e. | must immediately follow the previous match),
  • |(?<=\[x]\s[?!\s]\s\|) - or a location that is immediately preceded with [x] + a whitespace + a ?, ! or whitespace + a whitespace and | char
• ) - end of the group
• \K - match reset operator that removes the text matched so far from the overall match memory buffer
• ([^|\n]*) - zero or more chars other than | and a line feed char
• (?=\|) - a | char must appear immediately to the right of the current location.