fix: Add missing check for default frontend folder existence (#18872)

* fix: Add missing check for default frontend folder existence

* Add legacy location to plugins

* Fix incorrect relative path in Gradle plugin

* add unit tests

* add unit test for gradle

flow-plugins/flow-gradle-plugin/src/functionalTest/kotlin/com/vaadin/gradle/VaadinSmokeTest.kt

@@ -74,6 +74,13 @@ class VaadinSmokeTest : AbstractGradleTest() {
         expect(false, buildInfo.toJson()) { buildInfo.getBoolean(InitParameters.SERVLET_PARAMETER_PRODUCTION_MODE) }
     }
 
+    @Test
+    fun testPrepareFrontend_legacyFrontendFolder_usesLegacy() {
+        testProject.newFolder("frontend");
+        testProject.build("vaadinPrepareFrontend")
+        expect(true) { File(testProject.dir, "frontend/generated").exists() }
+    }
+
     @Test
     fun `vaadinBuildFrontend not ran by default in development mode`() {
         val result: BuildResult = testProject.build("build")

flow-plugins/flow-gradle-plugin/src/main/kotlin/com/vaadin/gradle/VaadinFlowPluginExtension.kt

@@ -314,7 +314,7 @@ public class PluginEffectiveConfiguration(
         .convention(project.projectDir)
 
     public val frontendDirectory: Provider<File> = extension.frontendDirectory
-        .convention(File(project.projectDir, FrontendUtils.DEFAULT_FRONTEND_DIR))
+        .convention(FrontendUtils.getLegacyFrontendFolderIfExists(project.projectDir, File(project.projectDir, FrontendUtils.DEFAULT_FRONTEND_DIR)))
 
     public val generateBundle: Provider<Boolean> = extension.generateBundle
         .convention(true)

flow-plugins/flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/FlowModeAbstractMojo.java

@@ -75,7 +75,7 @@ public abstract class FlowModeAbstractMojo extends AbstractMojo
     /**
      * A directory with project's frontend source files.
      */
-    @Parameter(defaultValue = "${project.basedir}/src/main/" + FRONTEND)
+    @Parameter(defaultValue = "${null}")
     private File frontendDirectory;
 
     /**
@@ -299,7 +299,13 @@ public boolean eagerServerLoad() {
 
     @Override
     public File frontendDirectory() {
-        return frontendDirectory;
+        if (frontendDirectory != null) {
+            return frontendDirectory;
+        }
+        File defaultFrontendFolder = new File(projectBasedir,
+                FrontendUtils.DEFAULT_FRONTEND_DIR);
+        return FrontendUtils.getLegacyFrontendFolderIfExists(projectBasedir,
+                defaultFrontendFolder);
     }
 
     @Override

flow-plugins/flow-maven-plugin/src/test/java/com/vaadin/flow/plugin/maven/PrepareFrontendMojoTest.java

@@ -42,6 +42,7 @@
 import com.vaadin.flow.server.Constants;
 import com.vaadin.flow.server.InitParameters;
 import com.vaadin.flow.server.frontend.FrontendTools;
+import com.vaadin.flow.server.frontend.FrontendUtils;
 import com.vaadin.flow.server.frontend.installer.NodeInstaller;
 
 import elemental.json.Json;
@@ -282,6 +283,24 @@ public void jarPackaging_copyProjectFrontendResources()
         Mockito.verify(project, Mockito.atLeastOnce()).getArtifacts();
     }
 
+    @Test
+    public void getFrontendFolder_legacyExists_propertyNotSet_returnsLegacy()
+            throws IllegalAccessException {
+        Assert.assertFalse(
+                new File(projectBase, FrontendUtils.DEFAULT_FRONTEND_DIR)
+                        .exists());
+        ReflectionUtils.setVariableValueInObject(mojo, "frontendDirectory",
+                null);
+        File legacyFrontend = new File(projectBase,
+                FrontendUtils.LEGACY_FRONTEND_DIR);
+        if (!legacyFrontend.mkdir()) {
+            Assert.fail("Failed to generate legacy frontend folder");
+        }
+        Assert.assertEquals(
+                "Expected legacy frontend folder to be used if exists",
+                legacyFrontend, mojo.frontendDirectory());
+    }
+
     private void assertPackageJsonContent() throws IOException {
         JsonObject packageJsonObject = getPackageJson(packageJson);
 

flow-plugins/flow-plugin-base/src/main/java/com/vaadin/flow/plugin/base/BuildFrontendUtil.java

@@ -147,7 +147,7 @@ public static void prepareFrontend(PluginAdapterBase adapter)
         Lookup lookup = adapter.createLookup(classFinder);
 
         Options options = new Options(lookup, adapter.npmFolder())
-                .withFrontendDirectory(getFrontendDirectory(adapter))
+                .withFrontendDirectory(adapter.frontendDirectory())
                 .withBuildDirectory(adapter.buildFolder())
                 .withJarFrontendResourcesFolder(
                         getJarFrontendResourcesFolder(adapter))
@@ -182,8 +182,7 @@ public static void prepareFrontend(PluginAdapterBase adapter)
     private static File getJarFrontendResourcesFolder(
             PluginAdapterBase adapter) {
         return new File(
-                new File(getFrontendDirectory(adapter),
-                        FrontendUtils.GENERATED),
+                new File(adapter.frontendDirectory(), FrontendUtils.GENERATED),
                 FrontendUtils.JAR_RESOURCES_FOLDER);
     }
 
@@ -232,7 +231,7 @@ public static File propagateBuildInfo(PluginAdapterBase adapter) {
                     e);
         }
         buildInfo.put(FRONTEND_TOKEN,
-                getFrontendDirectory(adapter).getAbsolutePath());
+                adapter.frontendDirectory().getAbsolutePath());
         buildInfo.put(CONNECT_JAVA_SOURCE_FOLDER_TOKEN,
                 adapter.javaSourceFolder().getAbsolutePath());
         buildInfo.put(JAVA_RESOURCE_FOLDER_TOKEN,
@@ -306,7 +305,7 @@ public static void runNodeUpdater(PluginAdapterBuild adapter)
         try {
             Options options = new com.vaadin.flow.server.frontend.Options(
                     lookup, adapter.npmFolder())
-                    .withFrontendDirectory(getFrontendDirectory(adapter))
+                    .withFrontendDirectory(adapter.frontendDirectory())
                     .withBuildDirectory(adapter.buildFolder())
                     .withRunNpmInstall(adapter.runNpmInstall())
                     .withWebpack(adapter.webpackOutputDirectory(),
@@ -372,7 +371,7 @@ public static void runDevBuildNodeUpdater(PluginAdapterBuild adapter)
         try {
             Options options = new com.vaadin.flow.server.frontend.Options(
                     lookup, adapter.npmFolder()).withProductionMode(false)
-                    .withFrontendDirectory(getFrontendDirectory(adapter))
+                    .withFrontendDirectory(adapter.frontendDirectory())
                     .withBuildDirectory(adapter.buildFolder())
                     .withRunNpmInstall(adapter.runNpmInstall())
                     .withWebpack(adapter.webpackOutputDirectory(),
@@ -413,25 +412,6 @@ public static void runDevBuildNodeUpdater(PluginAdapterBuild adapter)
         }
     }
 
-    /**
-     * Get the legacy frontend folder if available and new folder doesn't exist.
-     *
-     * @param adapter
-     *            PluginAdapterBase
-     * @return correct folder or legacy folder if not user defined
-     */
-    public static File getFrontendDirectory(PluginAdapterBase adapter) {
-        File frontendDir = adapter.frontendDirectory();
-        if (!frontendDir.exists() && frontendDir.toPath()
-                .endsWith(DEFAULT_FRONTEND_DIR.substring(2))) {
-            File legacy = new File(adapter.npmFolder(), LEGACY_FRONTEND_DIR);
-            if (legacy.exists()) {
-                return legacy;
-            }
-        }
-        return frontendDir;
-    }
-
     /**
      * The generated folder should be under frontend folder and will be moved to
      * the legacy package if not changed by the user.
@@ -445,8 +425,7 @@ public static File getGeneratedFrontendDirectory(
         if (adapter.generatedTsFolder().toPath()
                 .startsWith(adapter.frontendDirectory().toPath())) {
             // Possibly move frontend folder.
-            File frontendDirectory = getFrontendDirectory(adapter);
-            return new File(frontendDirectory, GENERATED);
+            return new File(adapter.frontendDirectory(), GENERATED);
         }
         // Return given generated folder
         return adapter.generatedTsFolder();

flow-server/src/main/java/com/vaadin/flow/server/frontend/FrontendUtils.java

@@ -596,18 +596,50 @@ public static File resolveFrontendPath(File projectRoot,
                 getFrontendFolder(projectRoot, deploymentConfiguration));
     }
 
-    private static File getFrontendFolder(File projectRoot,
+    /**
+     * Get the frontend folder location from configuration and fallbacks to
+     * {@link #LEGACY_FRONTEND_DIR} if it doesn't exist.
+     *
+     * @param projectRoot
+     *            project's root directory
+     * @param deploymentConfiguration
+     *            applications' configuration
+     * @return frontend folder location that is used by application to look for
+     *         frontend files
+     */
+    public static File getFrontendFolder(File projectRoot,
             AbstractConfiguration deploymentConfiguration) {
         String frontendFolderPath = deploymentConfiguration.getStringProperty(
-                FrontendUtils.PARAM_FRONTEND_DIR,
-                FrontendUtils.DEFAULT_FRONTEND_DIR);
+                PARAM_FRONTEND_DIR,
+                System.getProperty(PARAM_FRONTEND_DIR, DEFAULT_FRONTEND_DIR));
 
-        File f = new File(frontendFolderPath);
-        if (f.isAbsolute()) {
-            return f;
+        File frontendFolderFile = new File(frontendFolderPath);
+        if (!frontendFolderFile.isAbsolute()) {
+            frontendFolderFile = new File(projectRoot, frontendFolderPath);
         }
 
-        return new File(projectRoot, frontendFolderPath);
+        return getLegacyFrontendFolderIfExists(projectRoot, frontendFolderFile);
+    }
+
+    /**
+     * Get the legacy frontend folder if available and new folder doesn't exist.
+     *
+     * @param projectRoot
+     *            project's root directory
+     * @param frontendDir
+     *            the frontend directory location from project's configuration
+     * @return correct folder or legacy folder if not user defined
+     */
+    public static File getLegacyFrontendFolderIfExists(File projectRoot,
+            File frontendDir) {
+        if (!frontendDir.exists() && frontendDir.toPath()
+                .endsWith(DEFAULT_FRONTEND_DIR.substring(2))) {
+            File legacy = new File(projectRoot, LEGACY_FRONTEND_DIR);
+            if (legacy.exists()) {
+                return legacy;
+            }
+        }
+        return frontendDir;
     }
 
     /**

flow-server/src/main/java/com/vaadin/flow/server/frontend/ThemeUtils.java

@@ -78,9 +78,8 @@ public static Optional<String> getThemeName(VaadinContext context) {
             return getThemeAnnotation(context).map(Theme::value);
         } else {
             File themeJs;
-            String frontendFolderPath = config.getStringProperty(
-                    FrontendUtils.PARAM_FRONTEND_DIR,
-                    FrontendUtils.DEFAULT_FRONTEND_DIR);
+            String frontendFolderPath = FrontendUtils
+                    .getProjectFrontendDir(config).getPath();
             if (frontendFolderPath.startsWith("./")) {
                 themeJs = Paths.get(config.getProjectFolder().getPath(),
                         frontendFolderPath, FrontendUtils.GENERATED,

flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendUtilsTest.java

@@ -38,6 +38,7 @@
 import org.slf4j.LoggerFactory;
 
 import com.vaadin.flow.internal.Pair;
+import com.vaadin.flow.server.AbstractConfiguration;
 import com.vaadin.flow.server.ExecutionFailedException;
 import com.vaadin.flow.server.frontend.installer.NodeInstaller;
 import com.vaadin.flow.server.frontend.scanner.FrontendDependencies;
@@ -651,6 +652,22 @@ public void isHillaViewsUsed_noViews_false() throws IOException {
                 FrontendUtils.isHillaViewsUsed(frontend));
     }
 
+    @Test
+    public void getFrontendFolder_hasLegacyFolder_returnsLegacyFolder()
+            throws IOException {
+        File frontend = tmpDir.newFolder(FrontendUtils.LEGACY_FRONTEND_DIR);
+        AbstractConfiguration config = Mockito
+                .mock(AbstractConfiguration.class);
+        Mockito.when(config.getStringProperty(Mockito.anyString(),
+                Mockito.anyString()))
+                .thenReturn(FrontendUtils.DEFAULT_FRONTEND_DIR);
+        File resolvedFrontend = FrontendUtils
+                .getFrontendFolder(tmpDir.getRoot(), config);
+        Assert.assertEquals(
+                "Expected legacy frontend folder to be used if exists",
+                frontend, resolvedFrontend);
+    }
+
     private File prepareFrontendForRoutesFile(String fileName, String content)
             throws IOException {
         File frontend = tmpDir.newFolder(FrontendUtils.DEFAULT_FRONTEND_DIR);

vaadin-dev-server/src/main/java/com/vaadin/base/devserver/startup/DevModeInitializer.java

@@ -208,26 +208,19 @@ public static DevModeHandler initDevModeHandler(Set<Class<?>> classes,
                     new StatisticsSender(storage));
         }
 
-        String frontendFolder = config.getStringProperty(PARAM_FRONTEND_DIR,
-                System.getProperty(PARAM_FRONTEND_DIR, DEFAULT_FRONTEND_DIR));
-
-        // If new default frontend folder not exists check for legacy folder.
-        if (frontendFolder.endsWith(DEFAULT_FRONTEND_DIR)
-                && !new File(frontendFolder).exists()) {
-            File legacy = new File(baseDir, LEGACY_FRONTEND_DIR);
-            if (legacy.exists()) {
-                frontendFolder = LEGACY_FRONTEND_DIR;
-            }
-        }
+        File frontendFolder = FrontendUtils.getProjectFrontendDir(config);
+        String frontendGeneratedFolderPath = config.getStringProperty(
+                PROJECT_FRONTEND_GENERATED_DIR_TOKEN, FrontendUtils
+                        .getFrontendGeneratedFolder(frontendFolder).getPath());
+        File frontendGeneratedFolder = new File(frontendGeneratedFolderPath);
 
         Lookup lookupFromContext = context.getAttribute(Lookup.class);
         Lookup lookupForClassFinder = Lookup.of(new DevModeClassFinder(classes),
                 ClassFinder.class);
         Lookup lookup = Lookup.compose(lookupForClassFinder, lookupFromContext);
         Options options = new Options(lookup, baseDir)
-                .withFrontendDirectory(new File(frontendFolder))
-                .withFrontendGeneratedFolder(
-                        new File(frontendFolder + GENERATED))
+                .withFrontendDirectory(frontendFolder)
+                .withFrontendGeneratedFolder(frontendGeneratedFolder)
                 .withBuildDirectory(config.getBuildFolder());
 
         log().info("Starting dev-mode updaters in {} folder.",
@@ -273,13 +266,6 @@ public static DevModeHandler initDevModeHandler(Set<Class<?>> classes,
                         InitParameters.ADDITIONAL_POSTINSTALL_PACKAGES, "")
                 .split(",");
 
-        String frontendGeneratedFolderName = config.getStringProperty(
-                PROJECT_FRONTEND_GENERATED_DIR_TOKEN,
-                new File(frontendFolder).isAbsolute()
-                        ? Paths.get(frontendFolder, GENERATED).toString()
-                        : Paths.get(baseDir.getAbsolutePath(), frontendFolder,
-                                GENERATED).toString());
-        File frontendGeneratedFolder = new File(frontendGeneratedFolderName);
         File jarFrontendResourcesFolder = new File(frontendGeneratedFolder,
                 FrontendUtils.JAR_RESOURCES_FOLDER);
         JsonObject tokenFileData = Json.createObject();