Add baseline-immutables plugin to enable incremental compilation for …

…Immutables

README.md

@@ -24,6 +24,7 @@ _Baseline is a family of Gradle plugins for configuring Java projects with sensi
 | `com.palantir.baseline-encoding`              | Ensures projects use the UTF-8 encoding in compile tasks.
 | `com.palantir.baseline-release-compatibility` | Ensures projects targetting older JREs only compile against classes and methods available in those JREs.
 | `com.palantir.baseline-testing`               | Configures test tasks to dump heap dumps (hprof files) for convenient debugging
+| `com.palantir.baseline-immutables`            | Enables incremental compilation for the [Immutables](http://immutables.github.io/) annotation processor.
 
 See also the [Baseline Java Style Guide and Best Practices](./docs).
 
@@ -403,6 +404,14 @@ The plugin also adds a `checkJUnitDependencies` to make the migration to JUnit5
 3. For repos that use 'snapshot' style testing, it's convenient to have a single command to accept the updated snapshots after a code change.
 This plugin ensures that if you run tests with `./gradlew test -Drecreate=true`, the system property will be passed down to the running Java process (which can be detected with `Boolean.getBoolean("recreate")`).
 
+## com.palantir.baseline-immutables
+
+This plugin enables incremental compilation for the [Immutables](http://immutables.github.io/) annotation processor.
+
+This plugin adds the `-Aimmutables.gradle.incremental` compiler arg to the compile Java task for any source set whose annotation processor configuration contains the Immutables annotation processor.
+
+For more details, see the Immutables incremental compilation [tracking issue](https://github.com/immutables/immutables/issues/804).
+
 ## com.palantir.baseline-fix-gradle-java (off by default)
 
 Fixes up all Java [SourceSets](https://docs.gradle.org/current/userguide/building_java_projects.html#sec:java_source_sets)

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

@@ -48,6 +48,7 @@ public void apply(Project project) {
             proj.getPluginManager().apply(BaselineReleaseCompatibility.class);
             proj.getPluginManager().apply(BaselineTesting.class);
             proj.getPluginManager().apply(BaselineJavaParameters.class);
+            proj.getPluginManager().apply(BaselineImmutables.class);
 
             // TODO(dsanduleac): enable this when people's idea{} blocks no longer reference things like
             //    configurations.integrationTestCompile

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

@@ -0,0 +1,61 @@
+/*
+ * (c) Copyright 2021 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;
+
+import java.util.Objects;
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.plugins.JavaPluginConvention;
+import org.gradle.api.tasks.SourceSet;
+import org.gradle.api.tasks.compile.JavaCompile;
+
+public final class BaselineImmutables implements Plugin<Project> {
+
+    @Override
+    public void apply(Project project) {
+        project.getPluginManager().withPlugin("java", unused -> {
+            project.afterEvaluate(proj -> {
+                proj.getConvention().getPlugin(JavaPluginConvention.class).getSourceSets().stream()
+                        .filter(sourceSet -> hasImmutablesProcessor(project, sourceSet))
+                        .forEach(sourceSet -> addImmutablesIncrementalCompilerArg(project, sourceSet));
+            });
+        });
+    }
+
+    private static boolean hasImmutablesProcessor(Project project, SourceSet sourceSet) {
+        return project
+                .getConfigurations()
+                .getByName(sourceSet.getAnnotationProcessorConfigurationName())
+                .getDependencies()
+                .stream()
+                .anyMatch(BaselineImmutables::isImmutablesValue);
+    }
+
+    private static boolean isImmutablesValue(Dependency dep) {
+        return Objects.equals(dep.getGroup(), "org.immutables") && Objects.equals(dep.getName(), "value");
+    }
+
+    private static void addImmutablesIncrementalCompilerArg(Project project, SourceSet sourceSet) {
+        project.getTasks()
+                .named(sourceSet.getCompileJavaTaskName(), JavaCompile.class)
+                .get()
+                .getOptions()
+                .getCompilerArgs()
+                .add("-Aimmutables.gradle.incremental");
+    }
+}

gradle-baseline-java/src/main/resources/META-INF/gradle-plugins/com.palantir.baseline-immutables.properties

@@ -0,0 +1 @@
+implementation-class=com.palantir.baseline.plugins.BaselineImmutables