diff --git a/platforms/documentation/docs/src/docs/userguide/releases/upgrading/upgrading_version_8.adoc b/platforms/documentation/docs/src/docs/userguide/releases/upgrading/upgrading_version_8.adoc
index 710ff9675496..3b6e0a509565 100644
--- a/platforms/documentation/docs/src/docs/userguide/releases/upgrading/upgrading_version_8.adoc
+++ b/platforms/documentation/docs/src/docs/userguide/releases/upgrading/upgrading_version_8.adoc
@@ -47,6 +47,99 @@ JaCoCo has been updated to https://www.jacoco.org/jacoco/trunk/doc/changes.html[
 
 === Deprecations
 
+[[register_feature_main_source_set]]
+==== Deprecated calling `registerFeature` using the `main` source set
+
+Calling `link:{javadocPath}/org/gradle/api/plugins/JavaPluginExtension.html#registerFeature-java.lang.String-org.gradle.api.Action-[registerFeature]` on the `link:{javadocPath}/org/gradle/api/plugins/JavaPluginExtension.html[java]` extension using the `main` source set is deprecated and will change behavior in Gradle 9.0.
+
+Currently, features created while calling `link:{javadocPath}/org/gradle/api/plugins/FeatureSpec.html#usingSourceSet-org.gradle.api.tasks.SourceSet-[usingSourceSet]` with the `main` source set are initialized differently than features created while calling `usingSourceSet` with any other source set.
+Previously, when using the `main` source set, new `implementation`, `compileOnly`, `runtimeOnly`, `api`, and `compileOnlyApi` configurations were created, and the compile and runtime classpaths of the `main` source set were configured to extend these configurations.
+
+Starting in Gradle 9.0, the `main` source set will be treated like any other source set.
+With the `java-library` plugin applied (or any other plugin that applies the `java` plugin), calling `usingSourceSet` with the `main` source set will throw an exception.
+This is because the `java` plugin already configures a main feature.
+Only if the `java` plugin is not applied will the `main` source set be permitted when calling `usingSourceSet`.
+
+Code that currently registers features with the main source set, like so:
+=====
+[.multi-language-sample]
+======
+.build.gradle.kts
+[source,kotlin]
+----
+plugins {
+    id("java-library")
+}
+
+java {
+    registerFeature("feature") {
+        usingSourceSet(sourceSets["main"])
+    }
+}
+----
+======
+[.multi-language-sample]
+======
+.build.gradle
+[source,groovy]
+----
+plugins {
+    id("java-library")
+}
+
+java {
+    registerFeature("feature") {
+        usingSourceSet(sourceSets.main)
+    }
+}
+----
+======
+=====
+
+Should instead create a separate source set for the feature, and register the feature with that source set:
+=====
+[.multi-language-sample]
+======
+.build.gradle.kts
+[source,kotlin]
+----
+plugins {
+    id("java-library")
+}
+
+sourceSets {
+    create("feature")
+}
+
+java {
+    registerFeature("feature") {
+        usingSourceSet(sourceSets["feature"])
+    }
+}
+----
+======
+[.multi-language-sample]
+======
+.build.gradle
+[source,groovy]
+----
+plugins {
+    id("java-library")
+}
+
+sourceSets {
+    feature
+}
+
+java {
+    registerFeature("feature") {
+        usingSourceSet(sourceSets.feature)
+    }
+}
+----
+======
+=====
+
 [[deprecated_artifact_identifier]]
 ==== Deprecated `ArtifactIdentifier`
 The `ArtifactIdentifier` class has been deprecated for removal in Gradle 9.0.
diff --git a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaFeatureSpec.java b/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaFeatureSpec.java
index 28034229ec75..d3541c50f5a4 100644
--- a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaFeatureSpec.java
+++ b/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaFeatureSpec.java
@@ -18,16 +18,18 @@
 import org.gradle.api.InvalidUserCodeException;
 import org.gradle.api.capabilities.Capability;
 import org.gradle.api.internal.project.ProjectInternal;
+import org.gradle.api.plugins.FeatureSpec;
 import org.gradle.api.plugins.jvm.internal.DefaultJvmFeature;
 import org.gradle.api.plugins.jvm.internal.JvmFeatureInternal;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.internal.component.external.model.DefaultImmutableCapability;
 import org.gradle.internal.component.external.model.ProjectDerivedCapability;
+import org.gradle.internal.deprecation.DeprecationLogger;
 
 import java.util.LinkedHashSet;
 import java.util.Set;
 
-public class DefaultJavaFeatureSpec implements FeatureSpecInternal {
+public class DefaultJavaFeatureSpec implements FeatureSpec {
     private final String name;
     private final Set<Capability> capabilities = new LinkedHashSet<>(1);
     private final ProjectInternal project;
@@ -67,12 +69,10 @@ public void disablePublication() {
         allowPublication = false;
     }
 
-    @Override
     public boolean isPublished() {
         return allowPublication;
     }
 
-    @Override
     public JvmFeatureInternal create() {
         if (sourceSet == null) {
             throw new InvalidUserCodeException("You must specify which source set to use for feature '" + name + "'");
@@ -82,6 +82,14 @@ public JvmFeatureInternal create() {
             capabilities.add(new ProjectDerivedCapability(project, name));
         }
 
+        if (SourceSet.isMain(sourceSet)) {
+            DeprecationLogger.deprecateBehaviour(String.format("The '%s' feature was created using the main source set.", name))
+                .withAdvice("The main source set is reserved for production code and should not be used for features. Use another source set instead.")
+                .willBecomeAnErrorInGradle9()
+                .withUpgradeGuideSection(8, "deprecate_register_feature_main_source_set")
+                .nagUser();
+        }
+
         JvmFeatureInternal feature = new DefaultJvmFeature(name, sourceSet, capabilities, project, true, SourceSet.isMain(sourceSet));
         feature.withApi();
 
diff --git a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaPluginExtension.java b/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaPluginExtension.java
index 1214c518fa1b..fef9a26adedb 100644
--- a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaPluginExtension.java
+++ b/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/DefaultJavaPluginExtension.java
@@ -213,7 +213,7 @@ public boolean getAutoTargetJvmDisabled() {
      */
     @Override
     public void registerFeature(String name, Action<? super FeatureSpec> configureAction) {
-        FeatureSpecInternal spec = new DefaultJavaFeatureSpec(validateFeatureName(name), project);
+        DefaultJavaFeatureSpec spec = new DefaultJavaFeatureSpec(validateFeatureName(name), project);
         configureAction.execute(spec);
         JvmFeatureInternal feature = spec.create();
 
diff --git a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/FeatureSpecInternal.java b/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/FeatureSpecInternal.java
deleted file mode 100644
index 65b35b2f8b9b..000000000000
--- a/platforms/jvm/plugins-java-base/src/main/java/org/gradle/api/plugins/internal/FeatureSpecInternal.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Copyright 2019 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.gradle.api.plugins.internal;
-
-import org.gradle.api.plugins.FeatureSpec;
-import org.gradle.api.plugins.jvm.internal.JvmFeatureInternal;
-
-public interface FeatureSpecInternal extends FeatureSpec {
-    boolean isPublished();
-    JvmFeatureInternal create();
-}
diff --git a/platforms/jvm/plugins-java/src/integTest/groovy/org/gradle/api/plugins/JavaPluginTest.groovy b/platforms/jvm/plugins-java/src/integTest/groovy/org/gradle/api/plugins/JavaPluginTest.groovy
index b2bcb45e1ba3..d89b2e8fb010 100644
--- a/platforms/jvm/plugins-java/src/integTest/groovy/org/gradle/api/plugins/JavaPluginTest.groovy
+++ b/platforms/jvm/plugins-java/src/integTest/groovy/org/gradle/api/plugins/JavaPluginTest.groovy
@@ -474,23 +474,26 @@ class JavaPluginTest extends AbstractProjectBuilderSpec {
         project.pluginManager.apply(JavaPlugin)
         commonProject.pluginManager.apply(JavaPlugin)
         commonProject.group = "group"
-        commonProject.extensions.configure(JavaPluginExtension) {
-            it.registerFeature("other") {
-                it.usingSourceSet(commonProject.sourceSets.main)
+        commonProject.extensions.configure(JavaPluginExtension) { java ->
+            java.sourceSets.create("other")
+            java.registerFeature("other") {
+                it.usingSourceSet(java.sourceSets.other)
             }
         }
         middleProject.pluginManager.apply(JavaPlugin)
         middleProject.group = "group"
-        middleProject.extensions.configure(JavaPluginExtension) {
-            it.registerFeature("other") {
-                it.usingSourceSet(middleProject.sourceSets.main)
+        middleProject.extensions.configure(JavaPluginExtension) { java ->
+            java.sourceSets.create("other")
+            java.registerFeature("other") {
+                it.usingSourceSet(java.sourceSets.other)
             }
         }
         appProject.pluginManager.apply(JavaPlugin)
         appProject.group = "group"
-        appProject.extensions.configure(JavaPluginExtension) {
-            it.registerFeature("other") {
-                it.usingSourceSet(appProject.sourceSets.main)
+        appProject.extensions.configure(JavaPluginExtension) { java ->
+            java.sourceSets.create("other")
+            java.registerFeature("other") {
+                it.usingSourceSet(java.sourceSets.other)
             }
         }
 
diff --git a/platforms/software/dependency-management/src/crossVersionTest/groovy/org/gradle/integtests/resolve/GradleMetadataJavaLibraryCrossVersionIntegrationTest.groovy b/platforms/software/dependency-management/src/crossVersionTest/groovy/org/gradle/integtests/resolve/GradleMetadataJavaLibraryCrossVersionIntegrationTest.groovy
index a8ee99c00dbf..e37f44c41526 100644
--- a/platforms/software/dependency-management/src/crossVersionTest/groovy/org/gradle/integtests/resolve/GradleMetadataJavaLibraryCrossVersionIntegrationTest.groovy
+++ b/platforms/software/dependency-management/src/crossVersionTest/groovy/org/gradle/integtests/resolve/GradleMetadataJavaLibraryCrossVersionIntegrationTest.groovy
@@ -69,8 +69,11 @@ class GradleMetadataJavaLibraryCrossVersionIntegrationTest extends CrossVersionI
 
             java {
                 if (JavaPluginExtension.metaClass.respondsTo(delegate, 'registerFeature')) {
+                    sourceSets {
+                        hibernateSupport
+                    }
                     registerFeature("hibernateSupport") {
-                        usingSourceSet(sourceSets.main)
+                        usingSourceSet(sourceSets.hibernateSupport)
                         capability("com.acme", "producer-hibernate-support", "1.0")
                     }
                 }
diff --git a/platforms/software/ivy/src/integTest/groovy/org/gradle/api/publish/ivy/IvyPublishFeaturesJavaPluginIntegTest.groovy b/platforms/software/ivy/src/integTest/groovy/org/gradle/api/publish/ivy/IvyPublishFeaturesJavaPluginIntegTest.groovy
index 193f64cc7122..82c9209bbc03 100644
--- a/platforms/software/ivy/src/integTest/groovy/org/gradle/api/publish/ivy/IvyPublishFeaturesJavaPluginIntegTest.groovy
+++ b/platforms/software/ivy/src/integTest/groovy/org/gradle/api/publish/ivy/IvyPublishFeaturesJavaPluginIntegTest.groovy
@@ -23,9 +23,13 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
         given:
         buildFile << """
 
+            sourceSets {
+                feature
+            }
+
             java {
                 registerFeature("feature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.feature)
                 }
             }
 
@@ -50,7 +54,7 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
             noMoreDependencies()
         }
         javaLibrary.parsedModuleMetadata.variant("featureRuntimeElements") {
-            assert files*.name == ['publishTest-1.9.jar']
+            assert files*.name == ['publishTest-1.9-feature.jar']
             dependency('org', 'optionaldep', '1.0')
             noMoreDependencies()
         }
@@ -65,7 +69,7 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
         resolveRuntimeArtifacts(javaLibrary) {
             optionalFeatureCapabilities << "org.gradle.test:publishTest-feature:1.0"
             withModuleMetadata {
-                expectFiles "publishTest-1.9.jar", "optionaldep-1.0.jar"
+                expectFiles "publishTest-1.9.jar", "publishTest-1.9-feature.jar", "optionaldep-1.0.jar"
             }
             withoutModuleMetadata {
                 // documents the current behavior - ivy does not use variant matching and hence the requested capability is ignored and the default configuration is selected
@@ -80,9 +84,13 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
         given:
         buildFile << """
 
+            sourceSets {
+                feature
+            }
+
             java {
                 registerFeature("feature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.feature)
                 }
             }
 
@@ -112,7 +120,7 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
             noMoreDependencies()
         }
         javaLibrary.parsedModuleMetadata.variant("featureRuntimeElements") {
-            assert files*.name == ["${name}-${version}.jar"]
+            assert files*.name == ["${name}-${version}-feature.jar"]
             dependency('org', 'optionaldep', '1.0')
             noMoreDependencies()
         }
@@ -127,7 +135,7 @@ class IvyPublishFeaturesJavaPluginIntegTest extends AbstractIvyPublishFeaturesJa
         resolveRuntimeArtifacts(javaLibrary) {
             optionalFeatureCapabilities << "$group:${name}-feature:1.0"
             withModuleMetadata {
-                expectFiles "${name}-${version}.jar", "optionaldep-1.0.jar"
+                expectFiles "${name}-${version}.jar", "${name}-${version}-feature.jar", "optionaldep-1.0.jar"
             }
             withoutModuleMetadata {
                 // documents the current behavior - ivy does not use variant matching and hence the requested capability is ignored and the default configuration is selected
diff --git a/platforms/software/maven/src/integTest/groovy/org/gradle/api/publish/maven/MavenPublishFeaturesJavaPluginIntegTest.groovy b/platforms/software/maven/src/integTest/groovy/org/gradle/api/publish/maven/MavenPublishFeaturesJavaPluginIntegTest.groovy
index 9489e73446e7..adbd62b473d1 100644
--- a/platforms/software/maven/src/integTest/groovy/org/gradle/api/publish/maven/MavenPublishFeaturesJavaPluginIntegTest.groovy
+++ b/platforms/software/maven/src/integTest/groovy/org/gradle/api/publish/maven/MavenPublishFeaturesJavaPluginIntegTest.groovy
@@ -23,9 +23,15 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
         given:
         buildFile << """
 
+            sourceSets {
+                feature
+            }
+
+            repositories { maven { url "${mavenRepo.uri}" } }
+
             java {
                 registerFeature("feature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.feature)
                 }
             }
 
@@ -53,7 +59,7 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
             noMoreDependencies()
         }
         javaLibrary.parsedModuleMetadata.variant("featureRuntimeElements") {
-            assert files*.name == ['publishTest-1.9.jar']
+            assert files*.name == ['publishTest-1.9-feature.jar']
             dependency('org', 'optionaldep', '1.0')
             noMoreDependencies()
         }
@@ -70,7 +76,7 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
         resolveRuntimeArtifacts(javaLibrary) {
             optionalFeatureCapabilities << "org.gradle.test:publishTest-feature:1.0"
             withModuleMetadata {
-                expectFiles "publishTest-1.9.jar", "optionaldep-1.0.jar"
+                expectFiles "publishTest-1.9.jar", "publishTest-1.9-feature.jar", "optionaldep-1.0.jar"
             }
             withoutModuleMetadata {
                 shouldFail {
@@ -87,9 +93,15 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
         given:
         buildFile << """
 
+            sourceSets {
+                feature
+            }
+
+            repositories { maven { url "${mavenRepo.uri}" } }
+
             java {
                 registerFeature("feature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.feature)
                 }
             }
 
@@ -119,7 +131,7 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
             noMoreDependencies()
         }
         javaLibrary.parsedModuleMetadata.variant("featureApiElements") {
-            assert files*.name == ["${name}-${version}.jar"]
+            assert files*.name == ["${name}-${version}-feature.jar"]
             noMoreDependencies()
         }
         javaLibrary.parsedModuleMetadata.variant("featureRuntimeElements") {
@@ -139,7 +151,7 @@ class MavenPublishFeaturesJavaPluginIntegTest extends AbstractMavenPublishFeatur
         resolveRuntimeArtifacts(javaLibrary) {
             optionalFeatureCapabilities << "$group:${name}-feature:1.0"
             withModuleMetadata {
-                expectFiles "${name}-${version}.jar", "optionaldep-1.0.jar"
+                expectFiles "${name}-${version}.jar", "${name}-${version}-feature.jar", "optionaldep-1.0.jar"
             }
             withoutModuleMetadata {
                 shouldFail {
diff --git a/subprojects/architecture-test/src/changes/archunit_store/internal-api-nullability.txt b/subprojects/architecture-test/src/changes/archunit_store/internal-api-nullability.txt
index f7aef39ee145..39754cc56de4 100644
--- a/subprojects/architecture-test/src/changes/archunit_store/internal-api-nullability.txt
+++ b/subprojects/architecture-test/src/changes/archunit_store/internal-api-nullability.txt
@@ -1025,7 +1025,6 @@ Class <org.gradle.api.plugins.internal.DefaultJavaPluginConvention> is not annot
 Class <org.gradle.api.plugins.internal.DefaultJavaPluginExtension$DefaultJavaResolutionConsistency> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (DefaultJavaPluginExtension.java:0)
 Class <org.gradle.api.plugins.internal.DefaultJavaPluginExtension> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (DefaultJavaPluginExtension.java:0)
 Class <org.gradle.api.plugins.internal.DefaultWarPluginConvention> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (DefaultWarPluginConvention.java:0)
-Class <org.gradle.api.plugins.internal.FeatureSpecInternal> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (FeatureSpecInternal.java:0)
 Class <org.gradle.api.plugins.internal.HelpBuiltInCommand> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (HelpBuiltInCommand.java:0)
 Class <org.gradle.api.plugins.internal.HelpTasksAutoApplyAction> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (HelpTasksAutoApplyAction.java:0)
 Class <org.gradle.api.plugins.internal.JavaConfigurationVariantMapping$UnpublishableArtifactTypeSpec> is not annotated (directly or via its package) with @org.gradle.api.NonNullApi in (JavaConfigurationVariantMapping.java:0)
diff --git a/subprojects/plugins/src/integTest/groovy/org/gradle/java/JavaLibraryFeatureCompilationIntegrationTest.groovy b/subprojects/plugins/src/integTest/groovy/org/gradle/java/JavaLibraryFeatureCompilationIntegrationTest.groovy
index e558f4c7435f..b0836d59cc25 100644
--- a/subprojects/plugins/src/integTest/groovy/org/gradle/java/JavaLibraryFeatureCompilationIntegrationTest.groovy
+++ b/subprojects/plugins/src/integTest/groovy/org/gradle/java/JavaLibraryFeatureCompilationIntegrationTest.groovy
@@ -39,9 +39,13 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         buildFile << """
             apply plugin: 'java-library'
 
+            sourceSets {
+                myFeature
+            }
+
             java {
                 registerFeature("myFeature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.myFeature)
                 }
             }
 
@@ -59,7 +63,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
                 }
             }
         """
-        file("src/main/java/com/bar/Bar.java") << """
+        file("src/myFeature/java/com/bar/Bar.java") << """
             package com.bar;
             import com.foo.Foo;
 
@@ -72,7 +76,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         """
 
         when:
-        succeeds ':compileJava'
+        succeeds ':compileMyFeatureJava'
 
         then:
         executedAndNotSkipped ':b:compileJava'
@@ -97,9 +101,13 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
 
             group = 'org.gradle.test'
 
+            sourceSets {
+                myFeature
+            }
+
             java {
                 registerFeature("myFeature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.myFeature)
                 }
             }
 
@@ -152,7 +160,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         """
         }
 
-        file("b/src/main/java/com/foo/Foo.java") << """
+        file("b/src/myFeature/java/com/foo/Foo.java") << """
             package com.foo;
             public class Foo {
                 public void foo() {
@@ -175,8 +183,8 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         succeeds ':compileJava'
 
         then:
-        executedAndNotSkipped ':b:compileJava', ':c:compileJava', ':d:compileJava', ':e:compileJava', ':f:compileJava'
-        packagingTasks(compileClasspathPackaging, 'b')
+        executedAndNotSkipped ':b:compileMyFeatureJava', ':c:compileJava', ':d:compileJava', ':e:compileJava', ':f:compileJava'
+        packagingTasks(compileClasspathPackaging, 'b', 'myFeature')
         packagingTasks(compileClasspathPackaging, 'c')
         packagingTasks(compileClasspathPackaging, 'd')
         packagingTasks(compileClasspathPackaging, 'e')
@@ -186,7 +194,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         succeeds 'clean', ':verifyClasspath'
 
         then:
-        executedAndNotSkipped ':b:jar', ':c:jar', ':d:jar', ':g:jar' // runtime
+        executedAndNotSkipped ':b:myFeatureJar', ':c:jar', ':d:jar', ':g:jar' // runtime
         packagingTasks(compileClasspathPackaging, 'e') // compile time only
         packagingTasks(compileClasspathPackaging, 'f') // compile time only
 
@@ -206,9 +214,13 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         file("b/build.gradle") << """
             apply plugin: 'java-library'
 
+            sourceSets {
+                myFeature
+            }
+
             java {
                 registerFeature("myFeature") {
-                    usingSourceSet(sourceSets.main)
+                    usingSourceSet(sourceSets.myFeature)
                 }
             }
 
@@ -246,7 +258,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
                 }
             }
         """
-        file("src/main/java/com/bar/Bar.java") << """
+        file("src/myFeature/java/com/bar/Bar.java") << """
             package com.bar;
             import com.foo.Foo;
 
@@ -262,9 +274,8 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         succeeds ':compileJava'
 
         then:
-        executedAndNotSkipped ':b:compileJava', ':c:compileJava'
+        executedAndNotSkipped ':b:compileJava'
         packagingTasks(compileClasspathPackaging, 'b')
-        packagingTasks(compileClasspathPackaging, 'c')
 
         when:
         succeeds 'clean', ':resolveRuntime'
@@ -492,6 +503,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         """
 
         when:
+        executer.expectDocumentedDeprecationWarning("The 'feat' feature was created using the main source set. This behavior has been deprecated. This will fail with an error in Gradle 9.0. The main source set is reserved for production code and should not be used for features. Use another source set instead. Consult the upgrading guide for further information: https://docs.gradle.org/current/userguide/upgrading_version_8.html#deprecate_register_feature_main_source_set")
         run 'test'
 
         then:
@@ -540,7 +552,44 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         executedAndNotSkipped ':compileMain211Java', ':compileMain212Java'
     }
 
-    def "creates configurations when using main source set and java-library is not applied" () {
+    def "creates main feature with main source set when java plugin not applied" () {
+        given:
+        buildFile << """
+            plugins {
+                id('java-base')
+            }
+
+            sourceSets {
+               main
+            }
+
+            configurations {
+                testCompileClasspath
+                testRuntimeClasspath
+            }
+
+            java {
+               registerFeature('main') {
+                  usingSourceSet(sourceSets.main)
+               }
+            }
+        """
+
+        when:
+        executer.expectDocumentedDeprecationWarning("The 'main' feature was created using the main source set. This behavior has been deprecated. This will fail with an error in Gradle 9.0. The main source set is reserved for production code and should not be used for features. Use another source set instead. Consult the upgrading guide for further information: https://docs.gradle.org/current/userguide/upgrading_version_8.html#deprecate_register_feature_main_source_set")
+        succeeds 'dependencies'
+
+        then:
+        outputContains("mainRuntimeOnly")
+        outputContains("mainCompileOnly")
+        outputContains("mainImplementation")
+        outputContains("mainApi")
+        outputContains("mainCompileOnlyApi")
+        outputContains("mainRuntimeElements")
+        outputContains("mainApiElements")
+    }
+
+    def "creates configurations when using main source set, non-main feature, java-library is not applied" () {
         given:
         buildFile << """
             plugins {
@@ -564,6 +613,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         """
 
         when:
+        executer.expectDocumentedDeprecationWarning("The 'feature' feature was created using the main source set. This behavior has been deprecated. This will fail with an error in Gradle 9.0. The main source set is reserved for production code and should not be used for features. Use another source set instead. Consult the upgrading guide for further information: https://docs.gradle.org/current/userguide/upgrading_version_8.html#deprecate_register_feature_main_source_set")
         succeeds 'dependencies'
 
         then:
@@ -590,6 +640,7 @@ class JavaLibraryFeatureCompilationIntegrationTest extends AbstractIntegrationSp
         """
 
         when:
+        executer.expectDocumentedDeprecationWarning("The 'main' feature was created using the main source set. This behavior has been deprecated. This will fail with an error in Gradle 9.0. The main source set is reserved for production code and should not be used for features. Use another source set instead. Consult the upgrading guide for further information: https://docs.gradle.org/current/userguide/upgrading_version_8.html#deprecate_register_feature_main_source_set")
         run 'dependencies'
 
         then: