Add errorprone check for immutables style collisions

baseline-error-prone/build.gradle

@@ -21,11 +21,14 @@ dependencies {
     testCompile 'org.assertj:assertj-core'
     testCompile 'org.jooq:jooq'
     testCompile 'com.palantir.tritium:tritium-registry'
+    testCompileOnly 'org.immutables:value::annotations'
     testImplementation 'org.junit.jupiter:junit-jupiter'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-migrationsupport'
 
     annotationProcessor 'com.google.auto.service:auto-service'
+    annotationProcessor 'org.immutables:value'
     compileOnly 'com.google.auto.service:auto-service'
+    compileOnly 'org.immutables:value::annotations'
 }
 
 // Incorrectly identifies tests as junit4 usage

baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/ImmutablesStyleCollision.java

@@ -0,0 +1,55 @@
+/*
+ * (c) Copyright 2020 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.errorprone;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.BugPattern.LinkType;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.matchers.ChildMultiMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.Matchers;
+import com.sun.source.tree.ClassTree;
+import org.immutables.value.Value;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "ImmutablesStyleCollision",
+        linkType = LinkType.CUSTOM,
+        link = "https://github.com/palantir/gradle-baseline#baseline-error-prone-checks",
+        severity = BugPattern.SeverityLevel.ERROR,
+        summary = "Immutables @Value.Style inline annotation should not be present alongside a Style "
+                + "meta-annotation, as there is no Style merging. You should either modify the "
+                + "meta-annotation, or add the meta-annotation's fields to your inline @Value.Style "
+                + "declaration.")
+public final class ImmutablesStyleCollision extends BugChecker implements BugChecker.ClassTreeMatcher {
+    private static final Matcher<ClassTree> INLINE_STYLE_ANNOTATION = Matchers.hasAnnotation(Value.Style.class);
+    private static final Matcher<ClassTree> STYLE_META_ANNOTATION =
+            Matchers.annotations(ChildMultiMatcher.MatchType.AT_LEAST_ONE, Matchers.hasAnnotation(Value.Style.class));
+    private static final Matcher<ClassTree> MATCHER = Matchers.allOf(INLINE_STYLE_ANNOTATION, STYLE_META_ANNOTATION);
+
+    @Override
+    public Description matchClass(ClassTree tree, VisitorState state) {
+        if (MATCHER.matches(tree, state)) {
+            return buildDescription(tree)
+                    .setMessage("Immutable type cannot have both inline @Value.Style and meta-annotation applied")
+                    .build();
+        }
+        return Description.NO_MATCH;
+    }
+}

baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/ImmutablesStyleCollisionTest.java

@@ -0,0 +1,63 @@
+/*
+ * (c) Copyright 2020 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.errorprone;
+
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Test;
+
+public class ImmutablesStyleCollisionTest {
+
+    @Test
+    public void testPass() {
+        helper().addSourceLines(
+                        "Person.java",
+                        "import org.immutables.value.Value;",
+                        "public interface Person {",
+                        "    String name();",
+                        "}")
+                .doTest();
+    }
+
+    @Test
+    public void testFail() {
+        helper().addSourceLines(
+                        "MyMetaAnnotation.java",
+                        "import org.immutables.value.Value;",
+                        "import java.lang.annotation.ElementType;",
+                        "import java.lang.annotation.Retention;",
+                        "import java.lang.annotation.RetentionPolicy;",
+                        "import java.lang.annotation.Target;",
+                        "import org.immutables.value.Value;",
+                        "@Target({ElementType.PACKAGE, ElementType.TYPE})\n",
+                        "@Retention(RetentionPolicy.CLASS)\n",
+                        "@Value.Style(visibility = Value.Style.ImplementationVisibility.PUBLIC)\n",
+                        "public @interface MyMetaAnnotation {}")
+                .addSourceLines(
+                        "Person.java",
+                        "import org.immutables.value.Value;",
+                        "@MyMetaAnnotation",
+                        "@Value.Style(with = \"with\")",
+                        "// BUG: Diagnostic contains: Immutable type cannot have both inline",
+                        "public interface Person {",
+                        "    String name();",
+                        "}")
+                .doTest();
+    }
+
+    private CompilationTestHelper helper() {
+        return CompilationTestHelper.newInstance(ImmutablesStyleCollision.class, getClass());
+    }
+}