extensions/configuration-editing/src/configurationEditingMain.ts/registerExtensionsCompletionsInExtensionsDocument
function registerExtensionsCompletionsInExtensionsDocument(): vscode.Disposable {
	return vscode.languages.registerCompletionItemProvider({ pattern: '**/extensions.json' }, {
		provideCompletionItems(document, position, _token) {
			const location = getLocation(document.getText(), document.offsetAt(position));
			const range = document.getWordRangeAtPosition(position) || new vscode.Range(position, position);
			if (location.path[0] === 'recommendations') {
				const extensionsContent = <IExtensionsContent>parse(document.getText());
				return provideInstalledExtensionProposals(extensionsContent && extensionsContent.recommendations || [], '', range, false);
			}
			return [];
		}
	});
}