Apply repositories only if PREFER_PROJECT

Author: alexander-yevsyukov

gradle-root-plugin/src/main/kotlin/io/spine/tools/gradle/root/RootPlugin.kt

@@ -24,6 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+@file:Suppress("UnstableApiUsage") // We need to use unstable settings API.
+
 package io.spine.tools.gradle.root
 
 import io.spine.tools.gradle.DslSpec
@@ -32,6 +34,9 @@ import io.spine.tools.gradle.project.ProjectPlugin
 import io.spine.tools.gradle.root.RootExtension.Companion.NAME
 import org.gradle.api.Project
 import org.gradle.api.file.Directory
+import org.gradle.api.initialization.resolve.RepositoriesMode
+import org.gradle.api.internal.GradleInternal
+import org.gradle.api.internal.SettingsInternal
 import org.gradle.api.plugins.ExtensionAware
 
 /**
@@ -40,7 +45,9 @@ import org.gradle.api.plugins.ExtensionAware
  * The extension is used by Gradle plugins of libraries that extend
  * the [root extension][RootExtension] with custom configuration DSL.
  *
- * The plugin also applies repositories [standard for Spine SDK][applyStandard] to the project.
+ * The plugin also applies repositories [standard for Spine SDK][applyStandard]
+ * to the project IFF `dependencyResolutionManagement.repositoriesMode` property set
+ * in `settings.gradle.kts` to [RepositoriesMode.PREFER_PROJECT] or assumed such.
  */
 public class RootPlugin :
     ProjectPlugin<RootExtension>(DslSpec(NAME, RootExtension::class)) {
@@ -61,14 +68,12 @@ public class RootPlugin :
     }
 
     /**
-     * Applies the plugin to the given [project] by forcing creation of the [extension].
-     *
-     * Also applies repositories [standard for Spine SDK][applyStandard].
+     * Applies the plugin to the given [project].
      */
     override fun apply(project: Project) {
         super.apply(project)
         createExtension()
-        project.repositories.applyStandard()
+        project.tryApplyStandardRepositories()
         check(extension != null) {
             "The extension of the `${this::class.simpleName}` has not been created."
         }
@@ -82,3 +87,30 @@ public class RootPlugin :
         public const val ID: String = "io.spine.root"
     }
 }
+
+/**
+ * Attempts to apply repositories [standard for Spine SDK][applyStandard] to the project
+ * by inspecting the `dependencyResolutionManagement.repositoriesMode` value set
+ * in `settings.gradle.kts`.
+ *
+ * If the value set explicitly or assumed as [RepositoriesMode.PREFER_PROJECT],
+ * the repositories are applied.
+ */
+private fun Project.tryApplyStandardRepositories() {
+    val settings = project.settings
+    if (settings == null) {
+        repositories.applyStandard()
+        return
+    }
+    val mode = settings.dependencyResolutionManagement.repositoriesMode.get()
+    if (mode == RepositoriesMode.PREFER_PROJECT) {
+        repositories.applyStandard()
+    }
+}
+
+private val Project.settings: SettingsInternal?
+    get() = try {
+        (project.gradle as GradleInternal).settings
+    } catch (_: IllegalStateException) {
+        null
+    }

gradle-root-plugin/src/test/kotlin/io/spine/tools/gradle/root/RootPluginSpec.kt

@@ -30,6 +30,7 @@ import io.kotest.matchers.collections.shouldContain
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.shouldNotBe
 import io.kotest.matchers.string.shouldContain
+import io.kotest.matchers.string.shouldNotContain
 import io.spine.tools.gradle.task.BaseTaskName
 import io.spine.tools.gradle.testing.Gradle
 import io.spine.tools.gradle.testing.Gradle.BUILD_SUCCESSFUL
@@ -93,6 +94,77 @@ internal class RootPluginSpec {
         urls shouldContain "https://europe-maven.pkg.dev/spine-event-engine/snapshots"
     }
 
+    @Test
+    fun `apply repositories if 'repositoriesMode' is 'PREFER_PROJECT'`(
+        @TempDir projectDir: File
+    ) {
+        Gradle.settingsFile.under(projectDir).writeText(
+            """
+            dependencyResolutionManagement {
+                repositoriesMode.set(RepositoriesMode.PREFER_PROJECT)
+            }
+            """.trimIndent()
+        )
+        Gradle.buildFile.under(projectDir).writeText(
+            """
+            plugins {
+                id("io.spine.root")
+            }
+            
+            tasks.register("checkRepos") {
+                doLast {
+                    if (project.repositories.isEmpty()) {
+                        println("NO_REPOS")
+                    } else {
+                        project.repositories.forEach { 
+                            println("REPO: " + it.name) 
+                        }
+                    }
+                }
+            }
+            """.trimIndent()
+        )
+
+        val result = runGradleBuild(projectDir, listOf("checkRepos"))
+        result.output shouldContain "REPO: MavenLocal"
+    }
+
+    @Test
+    fun `not apply repositories if 'repositoriesMode' is other than 'PREFER_PROJECT'`(
+        @TempDir projectDir: File
+    ) {
+        Gradle.settingsFile.under(projectDir).writeText(
+            """
+            dependencyResolutionManagement {
+                repositoriesMode.set(RepositoriesMode.PREFER_SETTINGS)
+            }
+            """.trimIndent()
+        )
+        Gradle.buildFile.under(projectDir).writeText(
+            """
+            plugins {
+                id("io.spine.root")
+            }
+            
+            tasks.register("checkRepos") {
+                doLast {
+                    if (project.repositories.isEmpty()) {
+                        println("NO_REPOS")
+                    } else {
+                        project.repositories.forEach { 
+                            println("REPO: " + it.name) 
+                        }
+                    }
+                }
+            }
+            """.trimIndent()
+        )
+
+        val result = runGradleBuild(projectDir, listOf("checkRepos"))
+        result.output shouldContain "NO_REPOS"
+        result.output shouldNotContain "REPO: MavenLocal"
+    }
+
     @Test
     fun `be applied via its ID`(@TempDir projectDir: File) {
         Gradle.buildFile.under(projectDir).writeText(