build: add 'feature.legacy-classpath' plugin (#85)

Signed-off-by: Jendrik Johannes <jendrik.johannes@gmail.com>

CHANGELOG.md

@@ -5,6 +5,7 @@
 * deactivate signing for Gradle plugin publishing if not explicitly turned on
 * update spotless-plugin-gradle to 7.0.2 (improves configuration cache compatibility)
 * update dependency-analysis-gradle-plugin to 2.7.0 (addresses Gradle deprecation)
+* add 'feature.legacy-classpath' convention plugin
 
 ## Version 0.3.0
 

src/main/descriptions/org.hiero.gradle.feature.legacy-classpath.txt

@@ -0,0 +1 @@
+Conventions to allow non-module Jars on the classpath if a framework is used that is not yet JPMS compatible (e.g. has split packages)

src/main/kotlin/org.hiero.gradle.feature.legacy-classpath.gradle.kts

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: Apache-2.0
+plugins { id("org.hiero.gradle.base.jpms-modules") }
+
+// Make sure 'org.gradlex.java-module-dependencies' is applied as the auto-apply through settings
+// may not happen in a non-module project
+apply(plugin = "org.gradlex.java-module-dependencies")
+
+extraJavaModuleInfo {
+    failOnMissingModuleInfo = false
+    failOnAutomaticModules = false
+}

src/test/kotlin/org/hiero/gradle/test/LegacyClasspathTest.kt

@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: Apache-2.0
+package org.hiero.gradle.test
+
+import org.assertj.core.api.Assertions.assertThat
+import org.gradle.testkit.runner.TaskOutcome
+import org.hiero.gradle.test.fixtures.GradleProject
+import org.junit.jupiter.api.Test
+
+class LegacyClasspathTest {
+
+    @Test
+    fun `can build a classpath-based application`() {
+        val p = GradleProject().withMinimalStructure()
+        p.moduleInfo.delete()
+        // explicitly register Module without module-info
+        p.settingsFile.appendText("""javaModules { module("product/module-a") }""")
+        p.dependencyVersionsFile(
+            """
+            plugins {
+                id("org.hiero.gradle.base.lifecycle")
+                id("org.hiero.gradle.base.jpms-modules")
+            }
+            dependencies { api(platform("com.google.cloud:libraries-bom:26.49.0")) }
+            """
+                .trimIndent()
+        )
+        p.aggregationBuildFile(
+            """
+            plugins { id("java") }
+            dependencies { implementation(project(":module-a")) }
+        """
+                .trimIndent()
+        )
+        p.file(
+            "gradle/modules.properties",
+            """
+            # Jars that are not yet modules
+            com.google.api.gax=com.google.api:gax
+            com.google.auth.oauth2=com.google.auth:google-auth-library-oauth2-http
+            com.google.cloud.core=com.google.cloud:google-cloud-core
+            com.google.cloud.storage=com.google.cloud:google-cloud-storage
+        """
+                .trimIndent()
+        )
+        p.moduleBuildFile(
+            """
+            plugins {
+                id("org.hiero.gradle.module.application")
+                id("org.hiero.gradle.feature.legacy-classpath")
+            }
+            mainModuleInfo {  
+                requires("com.google.api.gax")
+                requires("com.google.auth.oauth2")
+                requires("com.google.cloud.core")
+                requires("com.google.cloud.storage")
+            }
+        """
+                .trimIndent()
+        )
+
+        val result = p.run("assemble")
+
+        assertThat(result.task(":module-a:assemble")?.outcome).isEqualTo(TaskOutcome.SUCCESS)
+    }
+}

src/test/kotlin/org/hiero/gradle/test/fixtures/GradleProject.kt

@@ -25,7 +25,7 @@ class GradleProject {
 
     val descriptionTxt = file("product/description.txt")
     val moduleBuildFile = file("product/module-a/build.gradle.kts")
-    private val moduleInfo = file("product/module-a/src/main/java/module-info.java")
+    val moduleInfo = file("product/module-a/src/main/java/module-info.java")
     private val javaSourceFile =
         file("product/module-a/src/main/java/org/hiero/product/module/a/ModuleA.java")
 
@@ -61,7 +61,7 @@ class GradleProject {
         )
         aggregation.writeFormatted("""plugins { id("org.hiero.gradle.base.lifecycle") }""")
         versionFile.writeText("1.0")
-        toolchainVersionsFile.writeText("jdk=17.0.12")
+        toolchainVersionsFile.writeText("jdk=17.0.13")
         descriptionTxt.writeText("A module to test hiero-gradle-conventions")
         moduleInfoFile("module org.hiero.product.module.a {}")
         javaSourceFile(