test: Decrease webpack aggregate timeout for ComponentThemeLiveReload…

…IT (#12945)

On deletion of parent theme component css, webpack compilation
frequently fails due to an unexpected change notification for
theme-app-theme.generated.js (together with the file deletion)
that prevents theme regeneration.
Decreasing aggregate timeout seems to prevent that situation.

flow-tests/test-application-theme/test-theme-component-live-reload/src/test/java/com/vaadin/flow/uitest/ui/ComponentThemeLiveReloadIT.java

@@ -25,7 +25,6 @@
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 import org.openqa.selenium.By;
 import org.openqa.selenium.NoSuchElementException;
@@ -100,11 +99,17 @@ public void cleanUp() {
         }
     }
 
-    // ignored until resolved. See issue 11928
     @Test
-    @Ignore
     public void webpackLiveReload_newComponentStylesCreatedAndDeleted_stylesUpdatedOnFly() {
         open();
+
+        /*
+         * Access browser logs in order to clear them to avoid to check entries
+         * from a previous run if the test is flaky due to webpack file change
+         * detection during parent css deletion
+         */
+        getLogEntries(java.util.logging.Level.ALL);
+
         Assert.assertFalse(
                 "Border radius for themed component is not expected before "
                         + "applying the styles",

flow-tests/test-application-theme/test-theme-component-live-reload/webpack.config.js

@@ -0,0 +1,42 @@
+/**
+ * This file contains project specific customizations for the webpack build.
+ * It is autogenerated if it didn't exist or if it was made for an older
+ * incompatible version.
+ *
+ * Defaults are provided in an autogenerated webpack.generated.js file and used by this file.
+ * The webpack.generated.js file is overwritten on each build and no customization can be done there.
+ */
+const merge = require('webpack-merge');
+const flowDefaults = require('./webpack.generated.js');
+
+/**
+ * To change the webpack config, add a new configuration object in
+ * the merge arguments below:
+ */
+module.exports = merge(flowDefaults,
+  // Decrease aggregate timeout to avoid random duplicated
+  // theme-app-theme.generated.js file changes notification
+  // that makes compilation fail when deleting parent theme component css.
+  // see https://github.com/vaadin/flow/issues/11928#issuecomment-1031146480
+  {
+    watchOptions: {
+      aggregateTimeout: 5
+    }
+  }
+  // Override default configuration
+  // {
+  //   mode: 'development',
+  //   devtool: 'inline-source-map',
+  // },
+
+  // Add a custom plugin
+  // (install the plugin with `npm install --save-dev webpack-bundle-analyzer`)
+  // {
+  //   plugins: [
+  //     new require('webpack-bundle-analyzer').BundleAnalyzerPlugin({
+  //       analyzerMode: 'static'
+  //     })
+  //   ]
+  // },
+);
+