extensions/emmet/src/util.ts/getMappingForIncludedLanguages
export function getMappingForIncludedLanguages(): any {
	// Explicitly map languages that have built-in grammar in VS Code to their parent language
	// to get emmet completion support
	// For other languages, users will have to use `emmet.includeLanguages` or
	// language specific extensions can provide emmet completion support
	const MAPPED_MODES: Object = {
		'handlebars': 'html',
		'php': 'html'
	};

	const finalMappedModes = Object.create(null);
	let includeLanguagesConfig = vscode.workspace.getConfiguration('emmet')['includeLanguages'];
	let includeLanguages = Object.assign({}, MAPPED_MODES, includeLanguagesConfig ? includeLanguagesConfig : {});
	Object.keys(includeLanguages).forEach(syntax => {
		if (typeof includeLanguages[syntax] === 'string' && LANGUAGE_MODES[includeLanguages[syntax]]) {
			finalMappedModes[syntax] = includeLanguages[syntax];
		}
	});
	return finalMappedModes;
}