Export an object from the CSS-in-JS syntax (#4824)

lib/__tests__/syntaxes.test.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const syntaxes = require('../syntaxes/index');
+
+const inputs = Object.keys(syntaxes).map((name) => [
+	name,
+	require(`../syntaxes/syntax-${name}.js`), // directly require modules to bypass importLazy() in syntaxes/index.js
+]);
+
+describe('syntaxes', () => {
+	it.each(inputs)('syntax is an object with parse and stringify keys: %s', (name, module) => {
+		expect(module).toMatchObject({
+			parse: expect.any(Function),
+			stringify: expect.any(Function),
+		});
+	});
+});

lib/syntaxes/syntax-css-in-js.js

@@ -1,3 +1,3 @@
 'use strict';
 
-module.exports = require('@stylelint/postcss-css-in-js');
+module.exports = require('@stylelint/postcss-css-in-js')();