fix(loader): fix publicPath regression (#384)

Author: rmja

Diff for: src/loader.js

@@ -68,7 +68,7 @@ export function pitch(request) {
   const childFilename = '*'; // eslint-disable-line no-path-concat
   const publicPath =
     typeof options.publicPath === 'string'
-      ? options.publicPath.endsWith('/')
+      ? options.publicPath === '' || options.publicPath.endsWith('/')
         ? options.publicPath
         : `${options.publicPath}/`
       : typeof options.publicPath === 'function'

Diff for: test/cases/publicpath-emptystring/expected/main.css

@@ -0,0 +1,2 @@
+body { background: red; background-image: url(cd0bb358c45b584743d8ce4991777c42.svg); }
+

Diff for: test/cases/publicpath-emptystring/index.js

@@ -0,0 +1 @@
+import './style.css';

Diff for: test/cases/publicpath-emptystring/react.svg

@@ -0,0 +1 @@
+body { background: red; background-image: url(./react.svg); }

Diff for: test/cases/publicpath-emptystring/style.css

@@ -0,0 +1,37 @@
+import Self from '../../../src';
+
+module.exports = {
+  entry: './index.js',
+  module: {
+    rules: [
+      {
+        test: /\.css$/,
+        use: [
+          {
+            loader: Self.loader,
+            options: {
+              publicPath: '',
+            },
+          },
+          'css-loader',
+        ],
+      },
+      {
+        test: /\.(svg|png)$/,
+        use: [
+          {
+            loader: 'file-loader',
+            options: {
+              filename: '[name].[ext]',
+            },
+          },
+        ],
+      },
+    ],
+  },
+  plugins: [
+    new Self({
+      filename: '[name].css',
+    }),
+  ],
+};