fix issue in generated public path of manifest.json

- when using devServer and absolute URL for publicPath
- also add test case

lib/WebpackConfig.js

@@ -131,8 +131,8 @@ class WebpackConfig {
      * @returns {string}
      */
     getRealPublicPath() {
-        // if we're using webpack-dev-server, use it & add the publicPath
-        if (this.useDevServer()) {
+        // if we're using webpack-dev-server and have no absolute url, use it & add the publicPath
+        if (this.useDevServer() && !this.publicPath.includes('://')) {
             // avoid 2 middle slashes
             return this.runtimeConfig.devServerUrl.replace(/\/$/,'') + this.publicPath;
         }

test/config-generator.js

@@ -375,6 +375,23 @@ describe('The config-generator function', () => {
             expect(actualConfig.devServer).to.be.undefined;
         });
 
+        it('devServer and an absolute URL as publicPath', () => {
+            const config = createConfig();
+            config.runtimeConfig.useDevServer = true;
+            config.runtimeConfig.devServerUrl = 'http://localhost:8080/';
+            config.outputPath = isWindows ? 'C:\\tmp\\public' : '/tmp/public';
+            config.setManifestKeyPrefix('public');
+            config.setPublicPath('https://cdn.example.com');
+            config.addEntry('main', './main');
+
+            const actualConfig = configGenerator(config);
+            expect(actualConfig.output.publicPath).to.equal('https://cdn.example.com/');
+            expect(actualConfig.devServer).to.not.be.undefined;
+
+            const manifestPlugin = findPlugin(ManifestPlugin, actualConfig.plugins);
+            expect(manifestPlugin.opts.publicPath).to.equal('https://cdn.example.com/');
+        });
+
         it('devServer no hot mode', () => {
             const config = createConfig();
             config.runtimeConfig.useDevServer = true;