demo.js

    hookMonacoCompletionProvider(provider) {
        const provideCompletionItems = provider.prototype.provideCompletionItems;
        const owner = this;

        provider.prototype.provideCompletionItems = async function (model, position, context, token) {
            // reuse 'this' to preserve context through call (using apply)
            const result = await provideCompletionItems.apply(this, [model, position, context, token]);

            if (!result || !result.suggestions)
                return result;

            const suggestions = result.suggestions.filter(item => !item.label.startsWith("_"));

            for (const suggestion of suggestions) {
                if (owner.deprecatedCandidates.includes(suggestion.label)) {

                    // the following is time consuming on all suggestions, that's why we precompute deprecated candidate names in the definition worker to filter calls
                    const uri = suggestion.uri;
                    const worker = await this._worker(uri);
                    const model = monaco.editor.getModel(uri);
                    const details = await worker.getCompletionEntryDetails(uri.toString(), model.getOffsetAt(position), suggestion.label)

                    if (owner.isDeprecatedEntry(details)) {
                        suggestion.tags = [monaco.languages.CompletionItemTag.Deprecated];
                    }
                }
            }

            // add our own templates when invoked without context
            if (context.triggerKind == monaco.languages.CompletionTriggerKind.Invoke) {
                var template = {
                    label: '@template',
                    kind: monaco.languages.CompletionItemKind.Snippet,
                    documentation: "BlaBlaBla\nBlobloblo",
                    insertText: '///start-template \n alert(\'yo\') \n///end-template'
                }
                suggestions.push(template);
            }

            // preserve incomplete flag or force it when the definition is not yet analyzed
            const incomplete = (result.incomplete && result.incomplete == true) || owner.deprecatedCandidates.length == 0;

            return {
                suggestions: suggestions,
                incomplete: incomplete
            };
        }
    }