How to count lines of code (LOC) using IntelliJ IDEA?

title says everything plus: - development language Lua - code revision control system - Perforce (integrated with IntelliJ IDE)

Solution

You can hack it via the native, global search:

Ctrl + Shift + F (to open global search)
Use regex mode (check the .* checkbox)
In the searchbox, enter only a caret "^" (without the quotes)
You may want to limit the search to a specific directory, via the "directory" tab
Hit the "Open in Find Window" button on the bottom-right
If it asks whether you want to continue, press "Continue"

The number of lines is shown at the end of the "Found occurrences" sentence.

Notes:

In regex, the caret (^) denotes the start of a line, except when inside square brackets, in which case it denotes negation
If you wanted to count non-empty lines, you could instead use "^.*\S" (without quotes), which signifies "The start of a line (^), followed by any number of characters (except newline) (.*), followed by a non-whitespace character (\S)"