expose-gradle-api-as-test-repo.patch

diff --git a/subprojects/public-api/build.gradle.kts b/subprojects/public-api/build.gradle.kts
index 6843632f414..9aba37fbbf6 100644
--- a/subprojects/public-api/build.gradle.kts
+++ b/subprojects/public-api/build.gradle.kts
@@ -28,6 +28,7 @@ dependencies {
     externalApi(libs.groovy)
 }
 
+val testRepoLocation = layout.buildDirectory.dir("repos/test")
 publishing {
     publications {
         create<MavenPublication>("maven") {
@@ -46,6 +47,29 @@ publishing {
             }
         }
     }
+    repositories {
+        maven {
+            name = "test"
+            url = testRepoLocation.get().asFile.toURI()
+        }
+    }
+}
+
+val testRepoElements = configurations.consumable("testRepoElements") {
+    outgoing.artifact(testRepoLocation) {
+        builtBy( "publishMavenPublicationToTestRepository")
+    }
+    // TODO: De-duplicate this. See publish-public-libraries
+    attributes {
+        attribute(Usage.USAGE_ATTRIBUTE, project.objects.named(Usage.JAVA_RUNTIME))
+        attribute(Category.CATEGORY_ATTRIBUTE, project.objects.named(Category.LIBRARY))
+        attribute(LibraryElements.LIBRARY_ELEMENTS_ATTRIBUTE, project.objects.named("gradle-local-repository"))
+        attribute(Bundling.BUNDLING_ATTRIBUTE, project.objects.named(Bundling.EMBEDDED))
+    }
+}
+
+(components["gradleApi"] as AdhocComponentWithVariants).addVariantsFromConfiguration(testRepoElements.get()) {
+    mapToOptional() // The POM should not include dependencies of this configuration
 }
 
 // TODO De-duplicate this
diff --git a/testing/public-api-tests/build.gradle.kts b/testing/public-api-tests/build.gradle.kts
index ea3c311df4d..3ebd8f2bc17 100644
--- a/testing/public-api-tests/build.gradle.kts
+++ b/testing/public-api-tests/build.gradle.kts
@@ -1,3 +1,5 @@
+import gradlebuild.integrationtests.tasks.IntegrationTest
+
 /*
  * Copyright 2024 the original author or authors.
  *
@@ -22,6 +24,28 @@ plugins {
 //    id("gradlebuild.integration-tests")
 }
 
+val testRepo = configurations.dependencyScope("testRepo")
+val resolveTestRepo = configurations.resolvable("resolveTestRepo") {
+    attributes {
+        attribute(Usage.USAGE_ATTRIBUTE, project.objects.named(Usage.JAVA_RUNTIME))
+        attribute(Category.CATEGORY_ATTRIBUTE, project.objects.named(Category.LIBRARY))
+        attribute(LibraryElements.LIBRARY_ELEMENTS_ATTRIBUTE, project.objects.named("gradle-local-repository"))
+        attribute(Bundling.BUNDLING_ATTRIBUTE, project.objects.named(Bundling.EMBEDDED))
+    }
+}
+
 dependencies {
+    testRepo(project(":public-api"))
     integTestDistributionRuntimeOnly(project(":distributions-jvm"))
 }
+
+class ApiJarTestRepoLocationCommandLineArgumentProvider(val repoLocation: Provider<FileSystemLocation>) : CommandLineArgumentProvider {
+    override fun asArguments() =
+        listOf("-DintegTest.apiJarRepoLocation=${repoLocation.get().asFile.absolutePath}")
+}
+
+tasks.withType<IntegrationTest>() {
+    jvmArgumentProviders.add(ApiJarTestRepoLocationCommandLineArgumentProvider(
+        resolveTestRepo.flatMap { it.elements }.map { it.first() }
+    ))
+}
diff --git a/testing/public-api-tests/src/integTest/groovy/org/gradle/api/PublicApiIntegrationTest.groovy b/testing/public-api-tests/src/integTest/groovy/org/gradle/api/PublicApiIntegrationTest.groovy
index 48b2f047d09..39f127d63f7 100644
--- a/testing/public-api-tests/src/integTest/groovy/org/gradle/api/PublicApiIntegrationTest.groovy
+++ b/testing/public-api-tests/src/integTest/groovy/org/gradle/api/PublicApiIntegrationTest.groovy
@@ -20,10 +20,39 @@ import org.gradle.integtests.fixtures.AbstractIntegrationSpec
 
 class PublicApiIntegrationTest extends AbstractIntegrationSpec {
     void 'can use public API'() {
-        def apiJarLocation = System.getProperty('integTest.apiJarLocation')
+        def apiJarRepoLocation = System.getProperty('integTest.apiJarRepoLocation')
+        println("Using API jar: $apiJarRepoLocation")
+
+        buildKotlinFile << """
+            plugins {
+                id("java-library")
+            }
+
+            repositories {
+                maven {
+                    url = uri("$apiJarRepoLocation")
+                }
+            }
+
+            dependencies {
+                implementation("org.gradle.experimental:gradle-public-api:+")
+            }
+        """
+
+        file("src/main/java/org/example/PublishedApiTestPlugin.java") << """
+            package org.example;
+
+            import org.gradle.api.Plugin;
+            import org.gradle.api.Project;
+
+            public class PublishedApiTestPlugin implements Plugin<Project> {
+                public void apply(Project project) {
+                    project.getTasks().register("myTask", CustomTask.class);
+                }
+            }
+        """
 
-        println("Using API jar: $apiJarLocation")
         expect:
-        true
+        succeeds(":compileJava")
     }
 }