Recreated test for the issue https://github.com/eclipse/xtext/issues/2920

org.eclipse.xtext.builder.tests/META-INF/MANIFEST.MF

@@ -40,7 +40,7 @@ Import-Package: org.apache.log4j;version="1.2.24",
  org.junit.rules;version="4.13.2",
  org.junit.runner;version="4.13.2",
  org.junit.runners.model;version="4.13.2"
-Bundle-Activator: org.eclipse.xtext.builder.tests.internal.TestsActivator
+Bundle-Activator: org.eclipse.xtext.builder.tests.internal.TestsActivatorCustom
 Bundle-ActivationPolicy: lazy
 Export-Package: org.eclipse.xtext.builder.tests;version="2.34.0",
  org.eclipse.xtext.builder.tests.builderTestLanguage;version="2.34.0",

org.eclipse.xtext.builder.tests/plugin.xml

@@ -132,14 +132,31 @@
 			type="buildertestlanguage">
 		</parser>
 	</extension>
+	<extension
+		point="org.eclipse.emf.ecore.extension_parser">
+		<parser
+			class="org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageExecutableExtensionFactoryGH2920:org.eclipse.xtext.resource.IResourceFactory"
+			type="buildertestlanguageGH2920">
+		</parser>
+	</extension>
 	<extension point="org.eclipse.xtext.extension_resourceServiceProvider">
 		<resourceServiceProvider
 			class="org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageExecutableExtensionFactory:org.eclipse.xtext.ui.resource.IResourceUIServiceProvider"
 			uriExtension="buildertestlanguage">
 		</resourceServiceProvider>
 	</extension>
+	<extension point="org.eclipse.xtext.extension_resourceServiceProvider">
+		<resourceServiceProvider
+			class="org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageExecutableExtensionFactoryGH2920:org.eclipse.xtext.ui.resource.IResourceUIServiceProvider"
+			uriExtension="buildertestlanguageGH2920">
+		</resourceServiceProvider>
+	</extension>
 	<extension point="org.eclipse.xtext.builder.participant">
 		<participant
 			class="org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageExecutableExtensionFactory:org.eclipse.xtext.builder.IXtextBuilderParticipant"/>
 	</extension>
+	<extension point="org.eclipse.xtext.builder.participant">
+		<participant
+			class="org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageExecutableExtensionFactoryGH2920:org.eclipse.xtext.builder.IXtextBuilderParticipant"/>
+	</extension>
 </plugin>

org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/impl/GH2920Test.java

@@ -8,6 +8,12 @@
  *******************************************************************************/
 package org.eclipse.xtext.builder.impl;
 
+import static org.junit.Assert.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IFolder;
 import org.eclipse.core.resources.IProject;
@@ -21,18 +27,19 @@
 import org.junit.Before;
 import org.junit.Test;
 
-import static org.junit.Assert.assertFalse;
-
 import com.google.inject.Inject;
 
 /**
  * @author sherrmann - Initial contribution and API
+ * @author Lorenzo Bettini - make it appropriate for reproducing https://github.com/eclipse/xtext/issues/2920
  */
 public class GH2920Test extends AbstractParticipatingBuilderTest {
 	private IJavaProject javaProject;
-	
+
 	@Inject private IResourceDescriptionsProvider descriptionsProvider;
 
+	private List<String> descriptionsInOutputFolder = new ArrayList<>();
+
 	@Before
 	public void createProjectUnderTest() throws Exception {
 		javaProject = createJavaProject("NoResourceFromOutput");
@@ -43,7 +50,12 @@ public void createProjectUnderTest() throws Exception {
 	@Override
 	public void build(IBuildContext context, IProgressMonitor monitor) throws CoreException {
 		IResourceDescriptions resourceDescriptions = descriptionsProvider.getResourceDescriptions(context.getResourceSet());
-		resourceDescriptions.getAllResourceDescriptions().forEach(rd -> assertFalse(rd.getURI().toString().contains("bin")));
+		resourceDescriptions.getAllResourceDescriptions().forEach(
+			rd -> {
+				String uriString = rd.getURI().toString();
+				if (uriString.contains("bin"))
+					descriptionsInOutputFolder.add(uriString);
+			});
 		super.build(context, monitor);
 	}
 
@@ -54,14 +66,21 @@ public void testIncremental() throws Exception {
 		build();
 		startLogging();
 		createSomeBuilderRelatedFile(project, "Bar");
+		checkNoUrisInOutputFolder();
 	}
 
 	private IFile createSomeBuilderRelatedFile(IProject project, String name) throws CoreException {
 		IFolder folder = project.getProject().getFolder("src");
-		IFile file = folder.getFile(name + F_EXT);
+		IFile file = folder.getFile(name + F_EXT + "GH2920");
 		file.create(new StringInputStream("object "+name), true, monitor());
 		build();
 		return file;
 	}
-}
 
+	private void checkNoUrisInOutputFolder() {
+		if (!descriptionsInOutputFolder.isEmpty())
+			fail("unexpected resources in output folder:\n" +
+				descriptionsInOutputFolder.stream()
+					.collect(Collectors.joining("\n", "  ", "")));
+	}
+}

org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/tests/internal/TestsActivatorCustom.java

@@ -0,0 +1,71 @@
+/*******************************************************************************
+ * Copyright (c) 2024 itemis AG (http://www.itemis.eu) and others.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package org.eclipse.xtext.builder.tests.internal;
+
+import org.eclipse.xtext.Constants;
+import org.eclipse.xtext.builder.tests.BuilderTestLanguageRuntimeModule;
+import org.eclipse.xtext.builder.tests.ui.BuilderTestLanguageUiModule;
+import org.eclipse.xtext.ui.shared.JdtHelper;
+import org.eclipse.xtext.ui.util.IJdtHelper;
+
+import com.google.inject.Binder;
+import com.google.inject.Module;
+import com.google.inject.Provider;
+import com.google.inject.name.Names;
+
+/**
+ * This allows customizations in the UI, specific for some test scenarions, without creating new languages.
+ * 
+ * @author Lorenzo Bettini - Initial contribution and API
+ */
+public class TestsActivatorCustom extends TestsActivator {
+
+	public static final String ORG_ECLIPSE_XTEXT_BUILDER_TESTS_BUILDERTESTLANGUAGE_GH2920 = ORG_ECLIPSE_XTEXT_BUILDER_TESTS_BUILDERTESTLANGUAGE
+			+ "GH2920";
+
+	@Override
+	protected Module getRuntimeModule(String grammar) {
+		if (ORG_ECLIPSE_XTEXT_BUILDER_TESTS_BUILDERTESTLANGUAGE_GH2920.equals(grammar))
+			return new BuilderTestLanguageRuntimeModule() {
+				@Override
+				public void configureFileExtensions(Binder binder) {
+					if (properties == null || properties.getProperty(Constants.FILE_EXTENSIONS) == null)
+						binder.bind(String.class).annotatedWith(Names.named(Constants.FILE_EXTENSIONS))
+								.toInstance("buildertestlanguageGH2920");
+				}
+			};
+		return super.getRuntimeModule(grammar);
+	}
+
+	@Override
+	protected Module getUiModule(String grammar) {
+		if (ORG_ECLIPSE_XTEXT_BUILDER_TESTS_BUILDERTESTLANGUAGE_GH2920.equals(grammar))
+			return new BuilderTestLanguageUiModule(this) {
+				/**
+				 * By default, the {@link IJdtHelper} is bound by the {@link org.eclipse.xtext.ui.shared.SharedStateModule}, but since the
+				 * UI module is mixed as the last one in {@link TestsActivator}, we can "override" its binding here.
+				 */
+				@SuppressWarnings("unused")
+				public Provider<IJdtHelper> provideJdtHelper() {
+					return new Provider<>() {
+						@Override
+						public IJdtHelper get() {
+							return new JdtHelper() {
+								@Override
+								protected boolean computeJavaCoreAvailable() {
+									return false;
+								}
+							};
+						}
+					};
+				}
+			};
+		return super.getUiModule(grammar);
+	}
+}

org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/tests/ui/BuilderTestLanguageExecutableExtensionFactoryGH2920.java

@@ -0,0 +1,29 @@
+/*******************************************************************************
+ * Copyright (c) 2024 itemis AG (http://www.itemis.eu) and others.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package org.eclipse.xtext.builder.tests.ui;
+
+import org.eclipse.xtext.builder.tests.internal.TestsActivator;
+import org.eclipse.xtext.builder.tests.internal.TestsActivatorCustom;
+
+import com.google.inject.Injector;
+
+/**
+ * This allows customizations in the UI, specific for some test scenarions, without creating new languages.
+ * 
+ * @author Lorenzo Bettini - Initial contribution and API
+ */
+public class BuilderTestLanguageExecutableExtensionFactoryGH2920 extends BuilderTestLanguageExecutableExtensionFactory {
+
+	@Override
+	protected Injector getInjector() {
+		TestsActivator activator = TestsActivator.getInstance();
+		return activator != null ? activator.getInjector(TestsActivatorCustom.ORG_ECLIPSE_XTEXT_BUILDER_TESTS_BUILDERTESTLANGUAGE_GH2920)
+				: null;
+	}
+}