How to use Regex to 'uppercase and replace' in Visual Studio Code's snippets?

Question

I want to create a snippet on Visual Studio Code 1.33.1 that create a C++ class using the file's name.
First, I want to set up the "include guard", the point is to use the file's name, replace every '.' by a '_' and set it all to uppercase (norm):
#ifndef FILE_CLASS_HPP //filename: File.class.hpp

The VSC documentation provides some variable for the file's name, and some Regex to change to all uppercase and replace a character by another.
Point is: I never managed to do both since I know nothing about Regex.

I tried to manually join the Regex but it never worked:
#ifndef ${TM_FILENAME/(.*)/${1:/upcase}/[\\.-]/_/g}

expected result:
#ifndef FILE_CLASS_HPP
actual result:
#ifndef ${TM_FILENAME/(.*)//upcase/[\.-]/_/g}

• Tim Biegeleisen: Visual Studio does not appear to support uppercasing via regex.
• tblaudez: @TimBiegeleisen The post you linked dates from 2012. You can see in the examples of the VSC Documentation that uppercasing using Regex is possible.
• Tim Biegeleisen: This is tough to do purely with regex. Do the #ifndef names have a fixed number of dots in them, or could there be an arbitrary number of dots?
• tblaudez: @TimBiegeleisen Unfortunately, the number of dots is arbitrary. It seems that there is a Regex to replace all occurrences of a character by another thought: [\\.-]/_/g. I just don't know how to combine it with the all uppercase Regex.
• Tim Biegeleisen: Yes, but the thing is, the regex you have in mind only works if you already have the string isolated and in hand, which is not the case here. For uppercasing, you have the same problem.

Answer 1

This should work:

"Filename upcase": {
 "prefix": "_uc",
 "body": [
 "#ifndef ${TM_FILENAME/([^\\.]*)(\\.)*/${1:/upcase}${2:+_}/g}"
 ],
 "description": "Filename uppercase and underscore"
},

---

([^\\.]*)(\\.)* group1: all characters before a period
 group2: the following period

replace with uppercase all the group1's: ${1:/upcase}

replace all the group2s ''s with _'s

The ${2:+_} is a conditional replacement, so you only add a _ at the end of group1 uppercase if there is a following group2.

The g global flag is necessary in this case to catch all the occurrences of group1group2's, not just the first.