What is the Lua patterns for this?

[Curculigo]

This is an example of the preprocessor syntax in the language I want to write syntax highlighting rules for:

@charset: utf8

I'm totally dumb about Lua patterns (and regular expressions, too).

Note: The rule in VSCode syntax highlighting is:

"match": "(?x)\n^\\s*(@[A-Za-z_]\\w*)\\s*(:\\s*\\w+\\s*)?$"

[SpartanJ]

RegEx is essentially correct, all vscode regex should work on ecode. But this particular one does something I wouldn't do on ecode because it's not needed and does not match how the parser works, but i think it's the only rule won't be equal on ecode: new lines don't need to be evaluated as part of the regex, alsp the (?x) is a flag and it's not needed for that specific regex, and the last ? is redundant, so in short:
^\\s*(@[A-Za-z_]\\w*)\\s*(:\\s*\\w+\\s*)$
would do the job in ecode (removed all the unnecessary stuff), although is a very simple regex that can be represented with lua patterns which are faster:
^%s*(@[%a_]%w*)%s*(%:%s*%w+%s*)$

RegEx and LuaPattern this time are essentially equal, Lua Patterns support some extra shorthand like %a for [A-Za-z] but both ways are valid, so:

^%s*(@[A-Za-z_]%w*)%s*(%:%s*%w+%s*)$
vs
^\\s*(@[A-Za-z_]\\w*)\\s*(:\\s*\\w+\\s*)$

the only thing that changes is that regex use backslash () as escape character and lua pattenrs use %.

The double backslash is because this was inside a string, the actual regex is:
^\s*(@[A-Za-z_]\w*)\s*(:\s*\w+\s*)$

I highly recommend learning pattern matching if you're interested in implementing new highlighters.
Lua Patterns particularly are really simple and can be learned in a day:
Follow the following reference: https://gitspartv.github.io/lua-patterns/ if you re interested. And for regex this is very useful: https://regex101.com/

Also to add:
Things between () are captures, these captures are used to use different highlight colors in vscode and ecode, so what it says here is:

(@word)(:word)
|_____||_____|
color 1 color 2

in a ecode definition that would be:
cpp case:

{ { "^%s*(@[A-Za-z_]%w*)%s*(%:%s*%w+%s*)$" }, { "normal", "keyword", "keyword2" } },

json:

    {
      "pattern": "^%s*(@[A-Za-z_]%w*)%s*(%:%s*%w+%s*)$",
      "type": [ "normal", "keyword", "keyword2" ]
    }

[Curculigo]

Your pattern is more perfect. But I found myself like this more:

    {
      "pattern": "^%s*@[%a_][%w_]*",
      "type": "keyword"
    },

It's personal taste after all.

I think I could archive the same with your pattern by changing keyword2 to normal.