java versions preview enhancements

changelog/@unreleased/pr-2376.v2.yml

@@ -0,0 +1,10 @@
+type: feature
+feature:
+  description: |-
+    java versions preview enhancements
+
+    + support setting preview on a project-by-project basis.
+    + Fixes #2340
+    + fails more elegantly if javaVersions is set on not-the-root.
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/2376

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/javaversions/BaselineJavaVersionExtension.java

@@ -57,6 +57,10 @@ public final void setTarget(int value) {
         target.set(ChosenJavaVersion.of(value));
     }
 
+    public final void setTarget(String value) {
+        target.set(ChosenJavaVersion.fromString(value));
+    }
+
     /** Runtime {@link ChosenJavaVersion} for testing and distributions. */
     public final Property<ChosenJavaVersion> runtime() {
         return runtime;
@@ -66,6 +70,10 @@ public final void setRuntime(int value) {
         runtime.set(ChosenJavaVersion.of(value));
     }
 
+    public final void setRuntime(String value) {
+        runtime.set(ChosenJavaVersion.fromString(value));
+    }
+
     /**
      * Overrides auto-detection if a value is present to force this module to be a
      * library ({@code true}) or a distribution {@code false}).

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/javaversions/BaselineJavaVersions.java

@@ -56,6 +56,9 @@ public void apply(Project project) {
         }
         BaselineJavaVersionsExtension rootExtension =
                 project.getExtensions().create(EXTENSION_NAME, BaselineJavaVersionsExtension.class, project);
+        project.subprojects(proj ->
+                proj.getExtensions().create(EXTENSION_NAME, SubprojectBaselineJavaVersionsExtension.class, proj));
+
         project.allprojects(proj -> proj.getPluginManager().withPlugin("java", unused -> {
             proj.getPluginManager().apply(BaselineJavaVersion.class);
             BaselineJavaVersionExtension projectVersions =

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/javaversions/BaselineJavaVersionsExtension.java

@@ -20,6 +20,7 @@
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicReference;
 import javax.inject.Inject;
+import org.gradle.api.GradleException;
 import org.gradle.api.Project;
 import org.gradle.api.provider.Property;
 import org.gradle.jvm.toolchain.JavaInstallationMetadata;
@@ -29,7 +30,7 @@
  * Extension named {@code javaVersions} on the root project used to configure all java modules
  * with consistent java toolchains.
  */
-public class BaselineJavaVersionsExtension {
+public class BaselineJavaVersionsExtension implements BaselineJavaVersionsExtensionSetters {
     private final Property<JavaLanguageVersion> libraryTarget;
     private final Property<ChosenJavaVersion> distributionTarget;
     private final Property<ChosenJavaVersion> runtime;
@@ -57,10 +58,22 @@ public final Property<JavaLanguageVersion> libraryTarget() {
         return libraryTarget;
     }
 
+    @Override
     public final void setLibraryTarget(int value) {
         libraryTarget.set(JavaLanguageVersion.of(value));
     }
 
+    @Override
+    public final void setLibraryTarget(String value) {
+        ChosenJavaVersion version = ChosenJavaVersion.fromString(value);
+        if (version.enablePreview()) {
+            throw new GradleException("Because code compiled with preview features cannot be run on newer JVMs, "
+                    + "(Java 15 preview cannot be run on Java 17, e.g.) it is unsuitable for use on projects that"
+                    + " are published as libraries.");
+        }
+        libraryTarget.set(version.javaLanguageVersion());
+    }
+
     /**
      * Target {@link ChosenJavaVersion} for compilation of code used within distributions,
      * but not published externally.
@@ -69,11 +82,13 @@ public final Property<ChosenJavaVersion> distributionTarget() {
         return distributionTarget;
     }
 
+    @Override
     public final void setDistributionTarget(int value) {
         distributionTarget.set(ChosenJavaVersion.of(value));
     }
 
     /** Accepts inputs such as '17_PREVIEW'. */
+    @Override
     public final void setDistributionTarget(String value) {
         distributionTarget.set(ChosenJavaVersion.fromString(value));
     }
@@ -83,11 +98,13 @@ public final Property<ChosenJavaVersion> runtime() {
         return runtime;
     }
 
+    @Override
     public final void setRuntime(int value) {
         runtime.set(ChosenJavaVersion.of(value));
     }
 
     /** Accepts inputs such as '17_PREVIEW'. */
+    @Override
     public final void setRuntime(String value) {
         runtime.set(ChosenJavaVersion.fromString(value));
     }
@@ -106,7 +123,7 @@ public final void jdks(LazyJdks lazyJdks) {
                 .map(javaInstallationMetadata -> ref -> ref.set(javaInstallationMetadata)));
     }
 
-    public interface LazyJdks {
+    interface LazyJdks {
         Optional<JavaInstallationMetadata> jdkFor(JavaLanguageVersion javaLanguageVersion, Project project);
     }
 }

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/javaversions/BaselineJavaVersionsExtensionSetters.java

@@ -0,0 +1,37 @@
+/*
+ * (c) Copyright 2022 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.baseline.plugins.javaversions;
+
+/**
+ * This exists to keep the setters on the 'BaselineJavaVersionsExtension' in sync with those on
+ * 'SubprojectBaselineJavaVersionsExtension'. Ideally it would have a name like 'BaselineJavaVersionsExtension'
+ * with the main one called 'RootProjectBaselineJavaVersionsExtension', but that class is public API and is depended
+ * on by other Gradle plugins.
+ */
+public interface BaselineJavaVersionsExtensionSetters {
+    void setLibraryTarget(int value);
+
+    void setLibraryTarget(String value);
+
+    void setDistributionTarget(int value);
+
+    void setDistributionTarget(String value);
+
+    void setRuntime(int value);
+
+    void setRuntime(String value);
+}

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/javaversions/SubprojectBaselineJavaVersionsExtension.java

@@ -0,0 +1,67 @@
+/*
+ * (c) Copyright 2022 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.baseline.plugins.javaversions;
+
+import javax.inject.Inject;
+import org.gradle.api.GradleException;
+import org.gradle.api.Project;
+
+public class SubprojectBaselineJavaVersionsExtension implements BaselineJavaVersionsExtensionSetters {
+    private final Project project;
+
+    @Inject
+    public SubprojectBaselineJavaVersionsExtension(Project project) {
+        this.project = project;
+    }
+
+    @Override
+    public final void setLibraryTarget(int _value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    @Override
+    public final void setLibraryTarget(String value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    @Override
+    public final void setDistributionTarget(int _value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    @Override
+    public final void setDistributionTarget(String _value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    @Override
+    public final void setRuntime(int _value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    @Override
+    public final void setRuntime(String _value) {
+        throw throwCannotSetFromSubproject();
+    }
+
+    private RuntimeException throwCannotSetFromSubproject() {
+        throw new GradleException("The javaVersions extension can only be used from the root project."
+                + " Did you mean javaVersion, which can be used to override on a project-by-project basis?"
+                + " You used it from "
+                + project.getName());
+    }
+}

gradle-baseline-java/src/test/groovy/com/palantir/baseline/BaselineJavaVersionIntegrationTest.groovy

@@ -147,6 +147,36 @@ class BaselineJavaVersionIntegrationTest extends IntegrationSpec {
         assertBytecodeVersion(compiledClass, JAVA_17_BYTECODE, ENABLE_PREVIEW_BYTECODE)
     }
 
+    def 'setting library target to preview version fails'() {
+        when:
+        buildFile << '''
+        javaVersions {
+            libraryTarget = '17_PREVIEW'
+        }
+        '''.stripIndent(true)
+        file('src/main/java/Main.java') << java17PreviewCode
+
+        then:
+        ExecutionResult result = runTasksWithFailure('compileJava', '-i')
+        result.standardError.contains 'cannot be run on newer JVMs'
+    }
+
+    def 'java 17 preview on single project works'() {
+        when:
+        buildFile << '''
+        javaVersion {
+            runtime = '17_PREVIEW'
+            target = '17_PREVIEW'
+        }
+        '''.stripIndent(true)
+        file('src/main/java/Main.java') << java17PreviewCode
+        File compiledClass = new File(projectDir, "build/classes/java/main/Main.class")
+
+        then:
+        runTasksSuccessfully('compileJava', '-i')
+        assertBytecodeVersion(compiledClass, JAVA_17_BYTECODE, ENABLE_PREVIEW_BYTECODE)
+    }
+
     def 'java 17 preview javadoc works'() {
         when:
         buildFile << '''
@@ -220,7 +250,7 @@ class BaselineJavaVersionIntegrationTest extends IntegrationSpec {
         when:
         buildFile << '''
         javaVersions {
-            libraryTarget = 11
+            libraryTarget = '11'
         }
         '''.stripIndent(true)
         file('src/main/java/Main.java') << java11CompatibleCode