Append lines of text after pattern using global command

Question

I'm reworking a section of logic in some C code to avoid a memory leak that looks like this:

switch (result) {
case CASE_1:
     return report(...);
case CASE_2:
     return report(...);
/*
 * More cases follow with the same pattern.
 */
}

I've used %s/return report/report/ to remove the return statements, but now I need to add a line with break; after that, so the final result resembles something like this:

switch (result) {
case CASE_1:
     report(...);
     break;
case CASE_2:
     report(...);
     break;
/*
 * More cases follow with the same pattern.
 */
}

I've tried using the global command to execute the append command with no success:

# Error "E448: Trailing characters" (potential bug in Vim?)
:g/report("/a\
     break;

# Appends nothing and does not wait for text to be input.
:g/report("/a

Trying the above in ex mode with Vim fails, and visual mode doesn't seem to work well with the insertion commands in general, regardless of the variant of vi. If I omit the global command, it will work: I can enter text and type a single "." character on a line by itself to return to command mode (or visual mode, depending on which mode I was in). However, this cannot be repeated using the . key in visual mode because it's an ex command, not a motion command.

In an unusual twist, the first attempt works in ex mode with the port of "The Traditional Vi" and even ed of all things, though nothing is auto-indented due to the usage of to the global command. That's fine anyway since the structure is predictable enough to manually insert indentation characters.

I've also attempted the following:

%s/report(".*$/&\
    break;/

This is the result of one line as displayed by Vim:

    report("No match");^@
break;

Can anybody explain how to use the global command with the append command to append one or even more than one line of text in Vim, even if I have to leave visual mode to do it?

Answer 1

If I understand your post correctly, you had this snippet of C code :

switch (result) {
case CASE_1:
     return report("...");
case CASE_2:
     return report("...");
}

And you wanted to transform it to :

switch (result) {
case CASE_1:
     report("...");
     break;
case CASE_2:
     report("...");
     break;
}

I don't know all the details of the global command, but here's how I would do it :

g/return report/normal! _dawobreak;

Explanation :

The global command searches the pattern return report, then on each line that matches this pattern, it executes the following command :

normal! _dawobreak;

The normal command types every character that follows as if we were in normal mode. Here it reads _dawobreak; as a sequence of keystrokes that can be broken down like this :

• _ = go to first non whitespace character
• daw = delete a word (including the space after it)
• o = open a new line under the current one
• break; = insert break;

The exclamation mark after the normal command, is to prevent recursiveness.
It means : if inside the sequence of keystrokes you detect a subsequence corresponding to a mapping, don't interpret it.

Answer 2

One way to do it is to use the widely underappreciated \zs:

:%s/report.*\zs/\r     break;/

What this does is, look at lines containing report, find end of line, and add a new line with break.

You could also achieve the same thing with global, but that would just complicate the command for no reason.