Enable PMD static analysis during the build

base/src/main/java/io/spine/base/Identifier.java

@@ -27,7 +27,6 @@
 import com.google.protobuf.StringValue;
 import io.spine.annotation.Internal;
 import io.spine.protobuf.AnyPacker;
-import io.spine.protobuf.Messages;
 import io.spine.protobuf.TypeConverter;
 import io.spine.string.StringifierRegistry;
 import org.checkerframework.checker.nullness.qual.Nullable;

base/src/main/java/io/spine/base/UuidFactory.java

@@ -22,7 +22,6 @@
 
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Internal;
 import com.google.protobuf.Message;
 import io.spine.protobuf.Messages;
 

base/src/main/java/io/spine/logging/Logging.java

@@ -63,7 +63,7 @@
         "ClassWithTooManyMethods"
         /* We provide shortcut methods for calling Slf4J Logger API. */,
 
-        "NewMethodNamingConvention"
+        "NewMethodNamingConvention", "PMD.MethodNamingConventions"
         /* These methods are prefixed with underscore to highlight the fact that these methods
            are for logging, and to make them more visible in the real code. */
 })

base/src/main/java/io/spine/reflect/PackageGraph.java

@@ -283,12 +283,8 @@ public boolean test(Package aPackage) {
                 return true;
             }
 
-            if (exclusions.stream()
-                          .anyMatch(packageName::startsWith)) {
-                return false;
-            }
-
-            return true;
+            return exclusions.stream()
+                             .noneMatch(packageName::startsWith);
         }
     }
 }

base/src/main/java/io/spine/validate/ComparableNumber.java

@@ -36,6 +36,7 @@ final class ComparableNumber extends Number implements Comparable<Number> {
 
     /** Creates a new instance from the specified number. */
     ComparableNumber(Number value) {
+        super();
         this.value = value;
     }
 

build.gradle

@@ -109,6 +109,7 @@ subprojects {
     }
 
     apply plugin: 'java-library'
+    apply plugin: 'pmd'
     apply plugin: 'com.google.protobuf'
     apply plugin: 'net.ltgt.errorprone'
 
@@ -215,6 +216,8 @@ subprojects {
     }
 
     clean.dependsOn cleanGenerated
+
+    apply from: deps.scripts.pmd
 }
 
 // IDEA project configuration.

testlib/src/main/java/io/spine/testing/UtilityClassTest.java

@@ -57,7 +57,7 @@ void hasUtilityConstructor() {
 
     @Test
     @DisplayName("not accept nulls in public static methods if the arg is non-Nullable")
-    @SuppressWarnings("PMD.JUnitTestsShouldIncludeAssertRule")
+    @SuppressWarnings("PMD.JUnitTestsShouldIncludeAssert")
         /* This test does assert via `NullPointerTester. */
     void nullCheckPublicStaticMethods() {
         NullPointerTester tester = new NullPointerTester();

tools/model-compiler/src/main/java/io/spine/tools/compiler/annotation/ApiOption.java

@@ -213,7 +213,7 @@ private enum KnownOption {
         EXPERIMENTAL(new ApiOption(experimentalAll, experimentalType, null, experimental)),
         INTERNAL(new ApiOption(internalAll, internalType, null, internal));
 
-        @SuppressWarnings("NonSerializableFieldInSerializableClass")
+        @SuppressWarnings({"NonSerializableFieldInSerializableClass", "PMD.SingularField"})
             // This private enum should not be serialized.
         private final ApiOption option;
 

tools/model-compiler/src/main/java/io/spine/tools/compiler/annotation/ModuleAnnotator.java

@@ -243,7 +243,7 @@ public Builder add(Job job) {
          * @see #setInternalAnnotation
          */
         public Builder setInternalPatterns(ImmutableSet<@Regex String> patterns) {
-            this.internalPatterns = checkNotNull(patterns);;
+            this.internalPatterns = checkNotNull(patterns);
             return this;
         }
 
@@ -255,7 +255,7 @@ public Builder setInternalPatterns(ImmutableSet<@Regex String> patterns) {
          * @see #setInternalAnnotation
          */
         public Builder setInternalMethodNames(ImmutableSet<String> methodNames) {
-            this.internalMethodNames = checkNotNull(methodNames);;
+            this.internalMethodNames = checkNotNull(methodNames);
             return this;
         }
 

tools/model-compiler/src/main/java/io/spine/tools/gradle/compiler/Extension.java

@@ -48,7 +48,7 @@
 @SuppressWarnings({
         "PublicField", "WeakerAccess" /* Expose fields as a Gradle extension */,
         "ClassWithTooManyMethods" /* The methods are needed for handing default values. */,
-        "ClassWithTooManyFields" /* OK for a Gradle extension to have a flat structure. */})
+        "ClassWithTooManyFields", "PMD.TooManyFields" /* Gradle extensions are flat like this. */})
 public class Extension extends GradleExtension {
 
     /**

tools/model-compiler/src/main/java/io/spine/tools/gradle/compiler/GeneratedInterfaces.java

@@ -263,6 +263,7 @@ public static final class PostfixPattern extends FilePattern {
         private final String postfix;
 
         private PostfixPattern(String postfix) {
+            super();
             this.postfix = postfix;
         }
 

tools/model-compiler/src/main/java/io/spine/tools/gradle/compiler/PostfixInterfaceConfig.java

@@ -35,6 +35,7 @@ final class PostfixInterfaceConfig extends PatternInterfaceConfig {
     private final String postfix;
 
     PostfixInterfaceConfig(@Regex String postfix) {
+        super();
         this.postfix = postfix;
     }
 

tools/model-compiler/src/main/java/io/spine/tools/gradle/compiler/ProtocConfigurationPlugin.java

@@ -257,6 +257,7 @@ private enum ProtocPlugin {
         GRPC("grpc"),
         SPINE("spineProtoc");
 
+        @SuppressWarnings("PMD.SingularField") /* Accessed from the outer class. */
         private final String name;
 
         ProtocPlugin(String name) {

tools/plugin-base/src/main/java/io/spine/tools/gradle/GradleTask.java

@@ -43,6 +43,7 @@
  * <p>Instantiated via {@link Builder}, forces the new task to be added to
  * the Gradle build lifecycle.
  */
+@SuppressWarnings("PMD.MissingStaticMethodInNonInstantiatableClass") /* Instantiated via Builder. */
 public final class GradleTask {
 
     private final Task task;

tools/plugin-base/src/main/java/io/spine/tools/type/MergedDescriptorSet.java

@@ -37,7 +37,7 @@ public final class MergedDescriptorSet {
     private final FileSet fileSet;
 
     MergedDescriptorSet(FileDescriptorSet descriptorSet) {
-        this.descriptors = ImmutableSet.copyOf(descriptorSet.getFileList());;
+        this.descriptors = ImmutableSet.copyOf(descriptorSet.getFileList());
         this.fileSet = FileSet.ofFiles(descriptors);
     }
 

tools/proto-js-plugin/src/main/java/io/spine/js/generate/field/parser/FieldParser.java

@@ -20,7 +20,6 @@
 
 package io.spine.js.generate.field.parser;
 
-import com.google.protobuf.Descriptors;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import io.spine.code.proto.FieldDeclaration;
 import io.spine.js.generate.output.CodeLines;
@@ -64,7 +63,6 @@ static FieldParser parserFor(FieldDescriptor field, CodeLines jsOutput) {
         checkNotNull(jsOutput);
         FieldDeclaration fdecl = new FieldDeclaration(field);
         if (fdecl.isMessage()) {
-            Descriptors.Descriptor message = field.getMessageType();
             return MessageFieldParser.createFor(field, jsOutput);
         }
         if (fdecl.isEnum()) {