Monaco editor is an online editor with syntax highlighting. It offers syntax highlighting support for many languages by default.
But we might need custom syntax highlighting
to match our real life use-cases.
Unfortunately, there is no API available to extend the language configuration, Refer this comment
As per the advice, I have overwritten the output of the built-in tokenizer
Table of contents
How I Approached
- I took all the language configurations that is available in the monaco editor using the API monaco.languages.getLanguages()
- Then i filtered out my desired language (in my case, I took
javascript
) - There will a method named
loader()
, which will be available for most of the registered languages - On executing the loader, it will return an object containing 2 keys named ,the
configuration
andlanguage
- This language will hold the tokenizer data
- I took this tokenizer and
modified the certain parts with my custom tokens
- The modification is done in such a way, that the
base object reference is unaffected
Actual Code
const allLangs = await monaco.languages.getLanguages();
const { conf, language: jsLang } = allLangs.find(({ id }) => id ==='javascript').loader();
for (let key in customTokenizer) {
const value = customTokenizer[key];
if (key === 'tokenizer') {
for (let category in value) {
const tokenDefs = value[category];
if (!jsLang.tokenizer.hasOwnProperty(category)) {
jsLang.tokenizer[category] = [];
}
if (Array.isArray(tokenDefs)) {
jsLang.tokenizer[category].unshift.apply(jsLang.tokenizer[category], tokenDefs)
}
}
} else if (Array.isArray(value)) {
if (!jsLang.hasOwnProperty(key)) {
jsLang[key] = [];
}
jsLang[key].unshift.apply(jsLang[key], value)
}
}
Advantages
- In monaco-editor, the
javascript worker provides excellent code completions
, If we create a new language tokenizer, we might lose this suggestions. This method avoids the need for a new language, thus preserves the code completions - This custom tokenizer
follows the monaco editor’s monarch pattern
, So if you have already written custom tokenizers, it will be easy for migration - The tokens are added in such a way that
custom tokens are given high priority
and this can also be modified by altering theunshift
topush
injsLang keys
Limitations
As monaco editor some how stores the language configuration inside monaco instance, We have to overwrite the language configuration before creation of any model (or) editor
in that desired language
Take Away
This method is possible only because of monaco editor’s lazy loading feature
(thanks to monaco editor team), where it loads the language configuration only when a model (or) editor instance is created for that language
So if we can change the configuration of the language before monaco uses it we can achieve the desired customization
Github Link
Profile Link : PranomVignesh
Repository Link : Extend Language Configuration in Monaco Editor
Top comments (2)
languages
json
,plaintext
do not haveloader
function, how to add custom tokenizer to json ?This example is done for the monaco-editor@0.20.0. In the latest version of monaco-editor@0.21.2 , They have added a new API 'registerDocumentSemanticTokensProvider'.
Please refer this link - microsoft.github.io/monaco-editor/...