refactor: enables icss only when css modules enabled (webpack#1103)

BREAKING CHANGE: `icss` plugin disable by default, you need to setup the `modules` option to enable it

Author: cap-Bernardito

src/index.js

@@ -35,27 +35,28 @@ export default function loader(content, map, meta) {
   const sourceMap = options.sourceMap || false;
   const plugins = [];
 
-  if (shouldUseModulesPlugins(options.modules, this.resourcePath)) {
-    plugins.push(...getModulesPlugins(options, this));
-  }
-
   const exportType = options.onlyLocals ? 'locals' : 'full';
   const preRequester = getPreRequester(this);
   const urlHandler = (url) =>
     stringifyRequest(this, preRequester(options.importLoaders) + url);
-  const icssResolver = this.getResolve({
-    mainFields: ['css', 'style', 'main', '...'],
-    mainFiles: ['index', '...'],
-  });
 
-  plugins.push(
-    icssParser({
-      context: this.context,
-      rootContext: this.rootContext,
-      resolver: icssResolver,
-      urlHandler,
-    })
-  );
+  if (shouldUseModulesPlugins(options.modules, this.resourcePath)) {
+    plugins.push(...getModulesPlugins(options, this));
+
+    const icssResolver = this.getResolve({
+      mainFields: ['css', 'style', 'main', '...'],
+      mainFiles: ['index', '...'],
+    });
+
+    plugins.push(
+      icssParser({
+        context: this.context,
+        rootContext: this.rootContext,
+        resolver: icssResolver,
+        urlHandler,
+      })
+    );
+  }
 
   if (options.import !== false && exportType === 'full') {
     const resolver = this.getResolve({

test/icss.test.js

@@ -16,7 +16,9 @@ const testCases = fs.readdirSync(testCasesPath);
 describe('ICSS', () => {
   testCases.forEach((name) => {
     it(`show work with the case "${name}"`, async () => {
-      const compiler = getCompiler(`./icss/tests-cases/${name}/source.js`);
+      const compiler = getCompiler(`./icss/tests-cases/${name}/source.js`, {
+        modules: 'global',
+      });
       const stats = await compile(compiler);
 
       expect(