Currently, it is not possible to build a new language as an extension of an existing one, the language-configuration.json file must be self-contained. This can lead to tedious maintenance as changes to the base language have to be forwarded manually. This package aims at helping language developers.

Assume you wand to derive a new language configuration from A-language-configuration.json, you just need to define a file let us say B.extension.language-configuration.json containing

{
    "extends": "path/to/A-language-configuration.json",
    "overrides": {
        "comments": {
            "blockComment": [
                "<!--",
                "-->"
            ]
        },
        "surroundingPairs": [
            ["{", "}"],
            ["[", "]"],
            ["(", ")"],
            ["\"", "\""],
            ["'", "'"],
            ["$", "$"],
            ["`", "`"],
            ["_", "_"],
            ["*", "*"]
        ],
    },
    "folding": {
        "offSide": true,
        "markers": {
            "start": "^\\s*<!--\\s*#?region\\b.*-->",
            "end": "^\\s*<!--\\s*#?endregion\\b.*-->"
        }
    }
}

• extends means that language B is based on the language configuration of language A. path/to/A-language-configuration.json can either be a relative local path to A-language-configuration.json or an url.
• The overrides section allows to replace some settings of A-language-configuration.json by their new values in B.
• Everything outside the overrides section is added to the B configuration. If the key already exists in A-language-configuration.json, it must be an array and in this case their contents are concatenated.

To obtain the self-contained language configuration file for B, B.language-configuration.json, use

const vel = require('vscode-extend-language')

vel.expandConfigurationFile('./B.extension.language-configuration.json', './B.language-configuration.json')