Allow plugin to be applied in settings.gradle

Resolves #5

Author: jjohannes

plugin/src/main/java/de/jjohannes/gradle/javaecosystem/capabilities/JavaEcosystemCapabilitiesPlugin.java

@@ -12,6 +12,8 @@
 import org.gradle.api.artifacts.ComponentVariantIdentifier;
 import org.gradle.api.artifacts.component.ModuleComponentIdentifier;
 import org.gradle.api.artifacts.dsl.ComponentMetadataHandler;
+import org.gradle.api.initialization.Settings;
+import org.gradle.api.plugins.ExtensionAware;
 import org.gradle.util.GradleVersion;
 
 import javax.annotation.Nullable;
@@ -24,30 +26,46 @@
 
 @SuppressWarnings("unused")
 @NonNullApi
-public abstract class JavaEcosystemCapabilitiesPlugin implements Plugin<Project> {
+public abstract class JavaEcosystemCapabilitiesPlugin implements Plugin<ExtensionAware> {
 
     private static final GradleVersion MINIMUM_SUPPORTED_VERSION = GradleVersion.version("6.0");
+    private static final GradleVersion MINIMUM_SUPPORTED_VERSION_SETTINGS = GradleVersion.version("6.8");
 
     /**
      * Map: Capability -> Default Module to resolve to (or 'null' if resolve to the highest version)
      */
     private final Map<String, String> standardResolutionStrategy = new HashMap<>();
 
     @Override
-    public void apply(Project project) {
+    public void apply(ExtensionAware projectOrSettings) {
         if (GradleVersion.current().compareTo(MINIMUM_SUPPORTED_VERSION) < 0) {
-            throw new IllegalStateException("Plugin requires at least Gradle 6.0");
+            throw new IllegalStateException("Plugin requires at least Gradle " + MINIMUM_SUPPORTED_VERSION.getVersion());
         }
 
         Set<String> allCapabilities = new TreeSet<>();
-        JavaEcosystemCapabilitiesExtension javaEcosystemCapabilities =
-                project.getExtensions().create("javaEcosystemCapabilities", JavaEcosystemCapabilitiesExtension.class, allCapabilities);
-        
-        registerCapabilityRules(project.getDependencies().getComponents(), allCapabilities);
-        registerComponentRules(project.getDependencies().getComponents());
-        
-        project.getConfigurations().all(configuration ->
-                defineStrategies(javaEcosystemCapabilities, configuration.getResolutionStrategy().getCapabilitiesResolution()));
+
+        ComponentMetadataHandler components;
+        if (projectOrSettings instanceof Project) {
+            components = ((Project) projectOrSettings).getDependencies().getComponents();
+        } else if (projectOrSettings instanceof Settings) {
+            if (GradleVersion.current().compareTo(MINIMUM_SUPPORTED_VERSION_SETTINGS) < 0) {
+                throw new IllegalStateException("Using this plugin in settings.gradle requires at least Gradle " + MINIMUM_SUPPORTED_VERSION_SETTINGS.getVersion());
+            }
+            //noinspection UnstableApiUsage
+            components = ((Settings) projectOrSettings).getDependencyResolutionManagement().getComponents();
+        } else {
+            throw new IllegalStateException("Cannot apply plugin to: " + projectOrSettings.getClass().getName());
+        }
+
+        registerCapabilityRules(components, allCapabilities);
+        registerComponentRules(components);
+
+        if (projectOrSettings instanceof Project) {
+            JavaEcosystemCapabilitiesExtension javaEcosystemCapabilities =
+                    projectOrSettings.getExtensions().create("javaEcosystemCapabilities", JavaEcosystemCapabilitiesExtension.class, allCapabilities);
+            ((Project) projectOrSettings).getConfigurations().all(configuration ->
+                    defineStrategies(javaEcosystemCapabilities, configuration.getResolutionStrategy().getCapabilitiesResolution()));
+        }
     }
 
     private void registerCapabilityRules(ComponentMetadataHandler components, Set<String> allCapabilities) {

plugin/src/test/groovy/de/jjohannes/gradle/javaecosystem/capabilities/test/SettingsTest.groovy

@@ -0,0 +1,81 @@
+package de.jjohannes.gradle.javaecosystem.capabilities.test
+
+import de.jjohannes.gradle.javaecosystem.capabilities.test.fixture.GradleBuild
+import spock.lang.Specification
+import spock.lang.Tag
+
+class SettingsTest extends Specification {
+
+    @Delegate
+    GradleBuild build = new GradleBuild()
+
+    @Tag("no-cross-version")
+    def "plugin can be applied in settings file"() {
+        given:
+        settingsFile << """
+            plugins {
+                id("de.jjohannes.java-ecosystem-capabilities")
+            }
+        """
+        buildFile << """
+            plugins {
+                id("java-library")
+            }
+            
+            repositories.mavenCentral()
+            
+            configurations.all {
+                resolutionStrategy.capabilitiesResolution {
+                    withCapability("cglib:cglib") {
+                        select("cglib:cglib:0")
+                    }
+                }
+                resolutionStrategy.capabilitiesResolution {
+                    withCapability("javax.mail:mail") {
+                       select("com.sun.mail:jakarta.mail:0")
+                    }
+                }
+                resolutionStrategy.capabilitiesResolution {
+                    withCapability("javax.ws.rs:jsr311-api") {
+                        select("org.jboss.resteasy:jaxrs-api:0")
+                    }
+                }
+                resolutionStrategy.capabilitiesResolution {
+                    withCapability("javax.servlet:servlet-api") {
+                        select("jakarta.servlet:jakarta.servlet-api:0")
+                    }
+                }
+            }
+            
+            dependencies {
+                implementation("cglib:cglib-nodep:3.2.10")
+                implementation("cglib:cglib:3.2.10")
+                implementation("com.sun.mail:jakarta.mail:2.0.1")
+                implementation("com.sun.mail:mailapi:2.0.1")
+                implementation("jakarta.servlet:jakarta.servlet-api:5.0.0")
+                implementation("org.apache.tomcat:tomcat-servlet-api:10.0.18")
+                implementation("org.jboss.resteasy:jaxrs-api:3.0.0.Final")
+                implementation("org.jboss.spec.javax.ws.rs:jboss-jaxrs-api_2.1_spec:2.0.2.Final")
+                implementation("org.jboss.spec.javax.ws.rs:jboss-jaxrs-api_3.0_spec:1.0.1.Final")
+            }
+        """
+
+        expect:
+        dependencies().output.contains '''
+            compileClasspath - Compile classpath for source set 'main'.
+            +--- cglib:cglib-nodep:3.2.10 -> cglib:cglib:3.2.10
+            |    +--- org.ow2.asm:asm:7.0
+            |    \\--- org.apache.ant:ant:1.10.3
+            |         \\--- org.apache.ant:ant-launcher:1.10.3
+            +--- cglib:cglib:3.2.10 (*)
+            +--- com.sun.mail:jakarta.mail:2.0.1
+            |    \\--- com.sun.activation:jakarta.activation:2.0.1
+            +--- com.sun.mail:mailapi:2.0.1 -> com.sun.mail:jakarta.mail:2.0.1 (*)
+            +--- jakarta.servlet:jakarta.servlet-api:5.0.0
+            +--- org.apache.tomcat:tomcat-servlet-api:10.0.18 -> jakarta.servlet:jakarta.servlet-api:5.0.0
+            +--- org.jboss.resteasy:jaxrs-api:3.0.0.Final
+            +--- org.jboss.spec.javax.ws.rs:jboss-jaxrs-api_2.1_spec:2.0.2.Final -> org.jboss.resteasy:jaxrs-api:3.0.0.Final
+            \\--- org.jboss.spec.javax.ws.rs:jboss-jaxrs-api_3.0_spec:1.0.1.Final -> org.jboss.resteasy:jaxrs-api:3.0.0.Final
+        '''.stripIndent()
+    }
+}