Reduce duplications (save complicated transforms for later use) in VScode snippets

Question

Is there a way to create custom variables inside a VScode snippet? I have these kind of snippets where I create a singleton, based on the name of a file and a folder.

Here's the snippet:

 "Service": {
   "prefix": "singletonByPath",
   "body": [
     "class ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/upcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g} {",
     "  $0",
     "}",
     "",
     "export const ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/downcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g} = new ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/upcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g}();",
     ""
   ],
   "description": "Create an exported singleton instance and a class based on the filename and path"
 },

So, when the snippet is triggered in a path like: '..../customers/service.ts' You will have this result:

class CustomersService {
  
}

export const customersService = new CustomersService();

The problem is that I have duplications of long hard to read regexes, and I would like to extract them to variables (or mirrors without tab stops).

I would even prefer having these variables in a "snippet-global location" so that I can use them in multiple snippets.

Is it possible to somehow reduce these duplications?

Answer 1

There are a couple of things you can do to simplify your snippet. There is no built-in way to save "variables" of pre-defined snippet parts.

Here though is a simplification of your code:

"Service": {
  "prefix": "singletonByPath",
  "body": [
    // "class ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/upcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g} {",

    "class ${1:${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/upcase}$2/g}}${2:${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g}} {",
            --                                                           --

    "  $0",
    "}",
    "",
    // "export const ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/downcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g} = new ${TM_DIRECTORY/.*[^\\w]([a-z])(\\w+)$/${1:/upcase}$2/g}${TM_FILENAME_BASE/([a-z])(\\w+)/${1:/upcase}$2/g}();",

    "export const ${1/(\\w+)/${1:/downcase}/}$2 = new $1$2();",

    ""
  ],
  "description": "Create an exported singleton instance and a class based on the filename and path"
}

Note the use of $1:${TM_DIRECTORY...} and likewise ${2:${TM_FILENAME_BASE...}

This effectively sets $1 to the result of the TM_DIRECTORY transform and $2 to the result of the TM_FILENAME_BASE transform and those "variables" can be used elsewhere in the snippet by just referring to $1 and $2.

Those "variables" can even be transformed themselves as in the ${1/(\\w+)/${1:/downcase}/} transform in the last line.

The last line of your snippet then becomes simply:

"export const ${1/(\\w+)/${1:/downcase}/}$2 = new $1$2();",

You will have to tab a couple of times because those "variables" are now tabstops, and the last transform won't be completed until you do tabstop past it, but that is a small price to pay for such a simplification.

---

There are other simplifications to your snippet that aren't "variable-related":

  "body": [
    "class ${1:${TM_DIRECTORY/.*[\\/\\\\](.*)/${1:/capitalize}/}}${2:${TM_FILENAME_BASE/(.*)/${1:/capitalize}/}} {",
    "  $0",
    "}",
    "",
    "export const ${1/(\\w+)/${1:/downcase}/g}$2 = new $1$2();",
    ""
  ],

You can use the capitalize transform. Also note that this last body works for Windows and linux path separators.