Regex to select indented lines preceded by one top blank line not working in Vim

Question

I made the regex:

/^\n\t(\n|.)*?\n$/gm

(prepended with \v inside Vim) to select consecutively indented lines (with tab) separated by a top blank line.

But while it works in other languages it doesn't seem to do in Vim.

I expect to get the following "underlined" parts highlighted:

A random fact:
_
____this_______
________should_
____be_________
____highlighted
_
Another random fact:
    this
        should
    NOT
    be
    highlighted

But what I get is:

A random fact:
_
____this_______
________should_
____be_________
____highlighted
_
_Another_random_fact:
____this_______
________should_
____NOT________
____be_________
____highlighted

What am I doing wrong?

Answer 1

There is a BUG in the given regex.

The given regex /^\n\t(\n|.)*?\n$/gm is going to match "newline & tab" at the starting , then it is going to match "newline or other character" which works across lines & hence it matches the lines which start with "other character" because that will be Preceded by "newline" !

Solution :
/^\n\t.*(\n\t.*)*\n$/gm
What this regex is trying :
Match "newline & tab" followed by "other characters" , then match "newline & tab" followed by "other characters" , terminating in "newline" not followed by "tab" which is the correct regex.

This will work.

Answer 2

I believe the last \n is eaten by the first occurrence

/^\n\t\(\n\|.\){-}\ze^\n/g

Or:

/\v^\n\t(\n|.){-}\ze^\n/g

Or:

/\v^\n\t\_.{-}\ze^\n/g

The {-} replace the * make the repetition non-greedy to avoid that two consecutive blocks are treated like one.

The \ze make the the last \n is not eaten.

The ^\n search for an ending blank line.