search for pattern and insert text that precedes the pattern from pattern1 to pattern2 exclusive

Question

basically I have a bunch of lines of code that all match the format .\module.variable (), .\module.variable2 (),

I want to take everything between the backslash and the space, before the parentheses and put it in the parentheses for each line, with whatever is on that line, like this: .\module.variable (module.variable), .\module.variable2 (module.variable2),

Answer 1

Visit each line that has the key pattern using the global command and do a (global) substitution on that same pattern at each visited line:

:g/\.\\\(\S\+\) ()/ s//.\\\1 (\1)/g

The pattern, which is used in both the global and substitution operations:

• \.\\ : period and backslash
• \(\S\+\) : non-empty, non-space string inside a capturing group (\(...\)) which allows us to reference the match in the replacement section of the substitution operation
• () : a space and empty pair of parens

We leave the pattern in the substitution operation empty which indicates that we want the last used pattern. The replacement part then just uses the capturing group back reference (\1) twice to build the target string. (Note: I don't think Vim help refers to these constructs as "capture/capturing groups" but it's pretty much a universally used term for them.)