VS Code: How to convert snippet placeholder to uppercase or lowercase?

问题

In VS Code, the docs for creating user defined snippets mentions some Grammar which includes options for /upcase, /downcase, and /capitalize, but I can't figure out how to use it.

I'm using the latest version of VS Code: Version 1.25.0 on Mac.

It seems like this snippet should convert the value of the placeholder to uppercase and to lowercase after typing it and hitting tab, but it doesn’t:

"test": {
    "prefix": "test",
    "body": "${1} -> ${1:/upcase} ${1:/downcase}"
},

Flow and Expected Result

1. type test
2. hit tab to get the snippet.

3. type Asdf to result in:

   Asdf -> Asdf Asdf
   

4. hit tab to get expected result of:

   Asdf -> ASDF asdf
   

Current Result

asdf -> asdf asdf

回答1:

Try this:

"test": {
    "prefix": "test",
    // "body": "${1} -> ${1/(.*)/${1:/upcase}/} > ${1/(.*)/${1:/downcase}/}"
    // simpler version below works too
    "body": "${1} -> ${1/(.*)/${1:/upcase} ${1:/downcase}/}"
}

You need to hit Tab to apply the transformation.

回答2:

For reference:

The integer in the EBNF docs refers to a RegExp group not to a tabstop reference so should work:

"test": {
    "prefix": "test",
    "body": "${1} -> ${1/(Asdf)/${1:/upcase}/} ${1/(Asdf)/${1:/downcase}/}"
}

来源：https://stackoverflow.com/questions/51272365/vs-code-how-to-convert-snippet-placeholder-to-uppercase-or-lowercase