possible solution

Author: mightyaleksey

node_modules/cool-styles/bar.css

@@ -2,15 +2,6 @@ import Core from './index.js'
 import fs from 'fs'
 import path from 'path'
 
-const escapedSeparator = path.sep.replace(/(.)/g, '\\$1');
-const relativePathPattern = new RegExp(`^.{1,2}$|^.{1,2}${escapedSeparator}`);
-
-// Checks if the path to the external module given
-const isModule = pathname => {
-  const parsed = path.parse( pathname );
-  return !parsed.root && !relativePathPattern.test( parsed.dir );
-}
-
 // Sorts dependencies in the following way:
 // AAA comes before AA and A
 // AB comes after AA and before A
@@ -42,26 +33,26 @@ export default class FileSystemLoader {
       trace = _trace || String.fromCharCode( this.importNr++ )
     return new Promise( ( resolve, reject ) => {
       let relativeDir = path.dirname( relativeTo ),
-        rootRelativePath = path.resolve( relativeDir, newPath ),
-        fileRelativePath = path.resolve( path.join( this.root, relativeDir ), newPath )
+        filename = path.resolve( this.root + relativeDir, newPath )
 
       // if the path is not relative or absolute, try to resolve it in node_modules
-      if (isModule(newPath)) {
+      if ( newPath[0] !== '.' && newPath[0] !== path.sep ) {
         try {
-          fileRelativePath = require.resolve( newPath );
+          filename = require.resolve( newPath );
         }
         catch (e) {}
       }
 
-      const tokens = this.tokensByFile[fileRelativePath]
-      if (tokens) { return resolve(tokens) }
+      const rootRelativePath = path.sep + path.relative( this.root, filename )
+      const tokens = this.tokensByFile[filename]
+      if ( tokens ) { return resolve( tokens ) }
 
-      fs.readFile( fileRelativePath, "utf-8", ( err, source ) => {
+      fs.readFile( filename, "utf-8", ( err, source ) => {
         if ( err ) reject( err )
         this.core.load( source, rootRelativePath, trace, this.fetch.bind( this ) )
           .then( ( { injectableSource, exportTokens } ) => {
             this.sources[trace] = injectableSource
-            this.tokensByFile[fileRelativePath] = exportTokens
+            this.tokensByFile[filename] = exportTokens
             resolve( exportTokens )
           }, reject )
       } )

node_modules/cool-styles/foo.css

@@ -1,4 +1,7 @@
-._compose_node_module_cool_styles_foo__example {
+:import("./bar.css") {
+  i__imported_example_0: example;
+}
+._node_modules_cool_styles_foo__example {
   color: #F00;
 }
 ._compose_node_module_source__foo {

src/file-system-loader.js

@@ -1,3 +1,3 @@
 {
-  "foo": "_compose_node_module_source__foo _compose_node_module_cool_styles_foo__example"
+  "foo": "_compose_node_module_source__foo _node_modules_cool_styles_foo__example _node_modules_cool_styles_foo__example i__imported_example_0"
 }