Easily reformatting function arguments onto multiple lines in Vim

Question

Particularly when editing legacy C++ code, I often find myself manually reformatting something like this:

SomeObject doSomething(firstType argumentOne, secondType argumentTwo, thirdType argumentThree);

to something like this:

SomeObject doSomething(firstType argumentOne,
                       secondType argumentTwo,
                       thirdType argumentThree);

Is there a builtin command to do this? If not, can someone suggest a plugin or provide some VimScript code for it? (J or gq can reverse the process very easily, so it need not go both ways.)

Answer 1

You can use splitjoin.

SomeObject doSomething(firstType argumentOne, secondType argumentTwo, thirdType argumentThree);

Inside or on brackets, type gS to split. You get:

SomeObject doSomething(firstType argumentOne,
    secondType argumentTwo,
    thirdType argumentThree);

You can also use vim-argwrap

Answer 2

Here's what I've put in my .vimrc. It is more flexible than @rbernabe's answer; it does the formatting based on the cinoptions global settings and simply breaks on commas (and so can be used on more than functions, if needed).

function FoldArgumentsOntoMultipleLines()
    substitute@,\s*@,\r@ge
    normal v``="
endfunction

nnoremap <F2> :call FoldArgumentsOntoMultipleLines()<CR>
inoremap <F2> <Esc>:call FoldArgumentsOntoMultipleLines()<CR>a

This maps F2 in normal and insert mode to doing a search and replace on the current line which converts all commas (with 0 or more spaces after each) into commas with a carriage return after each, then selects the whole group and indents it using the Vim builtin =.

A known shortcoming of this solution is for lines that include multiple template parameters (it breaks on their commas as well instead of just the commas of the normal parameters).