Rework how disabling of toolchain detection works

Disabling the toolchain detection by tasks wasn't sufficient,
because Gradle would use the nested `BaseImageOptions` as an input,
and even if the particular `JavaLauchner` input wasn't used if that
flag was disabled, it would still be used internally by Gradle to
snapshot inputs.

As a consequence, the fix only worked if Gradle actually detected
a GraalVM installation somewhere, even if it didn't use it!

To fix this, this commit introduces a top-level DSL method called
`disableToolchainDetection()` which effectively sets the toolchain
to `null` by convention. By making the toolchain optional and null
now Gradle wouldn't complain anymore.

Fixes #183

Author: melix

docs/src/docs/asciidoc/index.adoc

@@ -20,6 +20,7 @@ If you are interested in contributing, please refer to our https://github.com/gr
 ==== Gradle plugin
 
 * Fixed resource inference not working on custom binaries
+* Fixed `disableToolchainDetection` not working if a GraalVM installation isn't present. Please use `graalvmNative.disableToolchainDetection()` instead.
 
 === Release 0.9.8
 

docs/src/docs/snippets/gradle/groovy/build.gradle

@@ -59,8 +59,8 @@ graalvmNative {
 
 if (providers.environmentVariable("DISABLE_TOOLCHAIN").isPresent()) {
 // tag::disabling-toolchain[]
-    tasks.withType(org.graalvm.buildtools.gradle.tasks.BuildNativeImageTask).configureEach {
-        disableToolchainDetection = true
+    graalvmNative {
+        disableToolchainDetection()
     }
 // end::disabling-toolchain[]
 }

docs/src/docs/snippets/gradle/kotlin/build.gradle.kts

@@ -60,8 +60,8 @@ graalvmNative {
 
 if (providers.environmentVariable("DISABLE_TOOLCHAIN").isPresent()) {
 // tag::disabling-toolchain[]
-    tasks.withType<org.graalvm.buildtools.gradle.tasks.BuildNativeImageTask>().configureEach {
-        disableToolchainDetection.set(true)
+    graalvmNative {
+        disableToolchainDetection()
     }
 // end::disabling-toolchain[]
 }

native-gradle-plugin/src/main/java/org/graalvm/buildtools/gradle/dsl/GraalVMExtension.java

@@ -84,6 +84,18 @@ public interface GraalVMExtension {
      */
     void registerTestBinary(String name, Action<? super TestBinaryConfig> spec);
 
+    /**
+     * Enables detection of toolchains which support building native images.
+     * This is the default unless {@link #disableToolchainDetection()} was called.
+     */
+    void enableToolchainDetection();
+
+    /**
+     * Disables detection of toolchains, which is useful when the default detection
+     * mechanism isn't capable of handling your toolchain.
+     */
+    void disableToolchainDetection();
+
     interface TestBinaryConfig {
         /**
          * Sets the JVM test task which corresponds to the

native-gradle-plugin/src/main/java/org/graalvm/buildtools/gradle/internal/BaseNativeImageOptions.java

@@ -45,7 +45,6 @@
 import org.graalvm.buildtools.gradle.dsl.NativeResourcesOptions;
 import org.graalvm.buildtools.utils.SharedConstants;
 import org.gradle.api.Action;
-import org.gradle.api.JavaVersion;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.model.ObjectFactory;
 import org.gradle.api.provider.ListProperty;
@@ -60,10 +59,8 @@
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.TaskContainer;
-import org.gradle.jvm.toolchain.JavaLanguageVersion;
 import org.gradle.jvm.toolchain.JavaLauncher;
 import org.gradle.jvm.toolchain.JavaToolchainService;
-import org.gradle.jvm.toolchain.JvmVendorSpec;
 
 import javax.inject.Inject;
 import java.util.Arrays;
@@ -185,6 +182,7 @@ public String getName() {
      * to a Java launcher due to Gradle limitations.
      */
     @Nested
+    @Optional
     public abstract Property<JavaLauncher> getJavaLauncher();
 
     /**
@@ -218,14 +216,6 @@ public BaseNativeImageOptions(String name,
         getSharedLibrary().convention(false);
         getImageName().convention(defaultImageName);
         getUseFatJar().convention(SharedConstants.IS_WINDOWS);
-        getJavaLauncher().convention(
-                toolchains.launcherFor(spec -> {
-                    spec.getLanguageVersion().set(JavaLanguageVersion.of(JavaVersion.current().getMajorVersion()));
-                    if (GradleUtils.isAtLeastGradle7()) {
-                        spec.getVendor().set(JvmVendorSpec.matching("GraalVM"));
-                    }
-                })
-        );
     }
 
     private static Provider<Boolean> property(ProviderFactory providers, String name) {

native-gradle-plugin/src/main/java/org/graalvm/buildtools/gradle/internal/DefaultGraalVmExtension.java

@@ -45,9 +45,15 @@
 import org.graalvm.buildtools.gradle.dsl.GraalVMExtension;
 import org.graalvm.buildtools.gradle.dsl.NativeImageOptions;
 import org.gradle.api.Action;
+import org.gradle.api.JavaVersion;
 import org.gradle.api.NamedDomainObjectContainer;
 import org.gradle.api.Project;
+import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
+import org.gradle.jvm.toolchain.JavaLanguageVersion;
+import org.gradle.jvm.toolchain.JavaLauncher;
+import org.gradle.jvm.toolchain.JavaToolchainService;
+import org.gradle.jvm.toolchain.JvmVendorSpec;
 
 import javax.inject.Inject;
 import java.util.HashMap;
@@ -58,17 +64,41 @@ public abstract class DefaultGraalVmExtension implements GraalVMExtension {
     private final NativeImagePlugin plugin;
     private final Project project;
     private final Map<String, Provider<Boolean>> agentProperties = new HashMap<>();
+    private final Property<JavaLauncher> defaultJavaLauncher;
+    private final JavaToolchainService toolchainService;
 
     @Inject
     public DefaultGraalVmExtension(NamedDomainObjectContainer<NativeImageOptions> nativeImages,
                                    NativeImagePlugin plugin,
-                                   Project project) {
+                                   Project project,
+                                   JavaToolchainService toolchains) {
         this.nativeImages = nativeImages;
         this.plugin = plugin;
         this.project = project;
+        this.toolchainService = toolchains;
+        this.defaultJavaLauncher = project.getObjects().property(JavaLauncher.class);
+        enableToolchainDetection();
+        nativeImages.configureEach(options -> options.getJavaLauncher().convention(defaultJavaLauncher));
         getTestSupport().convention(true);
     }
 
+    @Override
+    public void enableToolchainDetection() {
+        defaultJavaLauncher.convention(
+                toolchainService.launcherFor(spec -> {
+                    spec.getLanguageVersion().set(JavaLanguageVersion.of(JavaVersion.current().getMajorVersion()));
+                    if (GradleUtils.isAtLeastGradle7()) {
+                        spec.getVendor().set(JvmVendorSpec.matching("GraalVM"));
+                    }
+                })
+        );
+    }
+
+    @Override
+    public void disableToolchainDetection() {
+        defaultJavaLauncher.convention((JavaLauncher) null);
+    }
+
     @Override
     public NamedDomainObjectContainer<NativeImageOptions> getBinaries() {
         return nativeImages;

native-gradle-plugin/src/main/java/org/graalvm/buildtools/gradle/tasks/BuildNativeImageTask.java

@@ -163,7 +163,7 @@ public void exec() {
             logger.lifecycle("Args are: " + args);
         }
         File executablePath = null;
-        if (getDisableToolchainDetection().get()) {
+        if (getDisableToolchainDetection().get() || !options.getJavaLauncher().isPresent()) {
             if (getGraalVMHome().isPresent()) {
                 String graalvmHome = getGraalVMHome().get();
                 getLogger().lifecycle("Toolchain detection is disabled, will use GraalVM from {}.", graalvmHome);