Merge pull request #1035 from jqno/kotlin-data-class

Improved Kotlin support

.gitignore

@@ -8,6 +8,7 @@ equalsverifier-release-verify/src/test/resources
 bin
 target
 .DS_Store
+kls_database.db
 
 # IntelliJ files
 .idea

CHANGELOG.md

@@ -13,6 +13,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Improved Kotlin support. ([Issue 506](https://github.com/jqno/equalsverifier/issues/506#issuecomment-2563664670))
+
 ## [3.18] - 2024-12-24
 
 ### Added

README.md

@@ -109,6 +109,7 @@ Here's a description of the modules:
 | equalsverifier-release-main   | release assembly for jar with dependencies                            |
 | equalsverifier-release-nodep  | release assembly for fat jar (with dependencies shaded in)            |
 | equalsverifier-release-verify | validation tests for the releases                                     |
+| equalsverifier-test-kotlin    | tests for Kotlin classes                                              |
 
 ## Signed JAR
 

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/checkers/FieldInspector.java

@@ -7,13 +7,16 @@
 public class FieldInspector<T> {
 
     private final Class<T> type;
+    private final boolean isKotlin;
 
-    public FieldInspector(Class<T> type) {
+    public FieldInspector(Class<T> type, boolean isKotlin) {
         this.type = type;
+        this.isKotlin = isKotlin;
     }
 
     public void check(FieldCheck<T> check) {
-        for (FieldProbe fieldProbe : FieldIterable.of(type)) {
+        FieldIterable it = isKotlin ? FieldIterable.ofKotlin(type) : FieldIterable.of(type);
+        for (FieldProbe fieldProbe : it) {
             check.execute(fieldProbe);
         }
     }

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/checkers/FieldsChecker.java

@@ -55,7 +55,7 @@ public FieldsChecker(Context<T> context) {
 
     @Override
     public void check() {
-        FieldInspector<T> inspector = new FieldInspector<>(context.getType());
+        FieldInspector<T> inspector = new FieldInspector<>(context.getType(), config.isKotlin());
 
         if (!context.getClassProbe().isEqualsInheritedFromObject()) {
             inspector.check(arrayFieldCheck);

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/checkers/NullChecker.java

@@ -18,7 +18,7 @@ public void check() {
             return;
         }
 
-        FieldInspector<T> inspector = new FieldInspector<>(context.getType());
+        FieldInspector<T> inspector = new FieldInspector<>(context.getType(), context.getConfiguration().isKotlin());
         inspector.check(new NullPointerExceptionFieldCheck<>(context));
     }
 }

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/reflection/FieldIterable.java

@@ -1,9 +1,8 @@
 package nl.jqno.equalsverifier.internal.reflection;
 
 import java.lang.reflect.Field;
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.List;
+import java.util.*;
+import java.util.stream.Collectors;
 
 /**
  * Iterable to iterate over all declared fields in a class and, if needed, over all declared fields of its superclasses.
@@ -13,12 +12,14 @@ public final class FieldIterable implements Iterable<FieldProbe> {
     private final Class<?> type;
     private final boolean includeSuperclasses;
     private final boolean includeStatic;
+    private final boolean isKotlin;
 
     /** Private constructor. Call {@link #of(Class)} or {@link #ofIgnoringSuper(Class)} instead. */
-    private FieldIterable(Class<?> type, boolean includeSuperclasses, boolean includeStatic) {
+    private FieldIterable(Class<?> type, boolean includeSuperclasses, boolean includeStatic, boolean isKotlin) {
         this.type = type;
         this.includeSuperclasses = includeSuperclasses;
         this.includeStatic = includeStatic;
+        this.isKotlin = isKotlin;
     }
 
     /**
@@ -29,7 +30,18 @@ private FieldIterable(Class<?> type, boolean includeSuperclasses, boolean includ
      * @return A FieldIterable.
      */
     public static FieldIterable of(Class<?> type) {
-        return new FieldIterable(type, true, true);
+        return new FieldIterable(type, true, true, false);
+    }
+
+    /**
+     * Factory method for a FieldIterable that iterates over all declared fields of {@code type} and over the declared
+     * fields of all of its superclasses, but that ignores overridden Kotlin backing fields in superclasses.
+     *
+     * @param type The class that contains the fields over which to iterate.
+     * @return A FieldIterable.
+     */
+    public static FieldIterable ofKotlin(Class<?> type) {
+        return new FieldIterable(type, true, true, true);
     }
 
     /**
@@ -40,7 +52,7 @@ public static FieldIterable of(Class<?> type) {
      * @return A FieldIterable.
      */
     public static FieldIterable ofIgnoringSuper(Class<?> type) {
-        return new FieldIterable(type, false, true);
+        return new FieldIterable(type, false, true, false);
     }
 
     /**
@@ -51,7 +63,7 @@ public static FieldIterable ofIgnoringSuper(Class<?> type) {
      * @return A FieldIterable.
      */
     public static FieldIterable ofIgnoringStatic(Class<?> type) {
-        return new FieldIterable(type, true, false);
+        return new FieldIterable(type, true, false, false);
     }
 
     /**
@@ -62,7 +74,7 @@ public static FieldIterable ofIgnoringStatic(Class<?> type) {
      * @return A FieldIterable.
      */
     public static FieldIterable ofIgnoringSuperAndStatic(Class<?> type) {
-        return new FieldIterable(type, false, false);
+        return new FieldIterable(type, false, false, false);
     }
 
     /**
@@ -76,6 +88,15 @@ public Iterator<FieldProbe> iterator() {
     }
 
     private List<FieldProbe> createFieldList() {
+        if (isKotlin) {
+            return createKotlinFieldList();
+        }
+        else {
+            return createJavaFieldList();
+        }
+    }
+
+    private List<FieldProbe> createJavaFieldList() {
         List<FieldProbe> result = new ArrayList<>();
 
         result.addAll(addFieldsFor(type));
@@ -89,6 +110,24 @@ private List<FieldProbe> createFieldList() {
         return result;
     }
 
+    private List<FieldProbe> createKotlinFieldList() {
+        List<FieldProbe> result = new ArrayList<>();
+
+        result.addAll(addFieldsFor(type));
+        Set<String> names = result.stream().map(FieldProbe::getName).collect(Collectors.toSet());
+
+        if (includeSuperclasses) {
+            for (Class<?> c : SuperclassIterable.of(type)) {
+                List<FieldProbe> superFields =
+                        addFieldsFor(c).stream().filter(p -> !names.contains(p.getName())).collect(Collectors.toList());
+                result.addAll(superFields);
+                superFields.stream().map(FieldProbe::getName).forEach(names::add);
+            }
+        }
+
+        return result;
+    }
+
     private List<FieldProbe> addFieldsFor(Class<?> c) {
         List<FieldProbe> fields = new ArrayList<>();
         List<FieldProbe> statics = new ArrayList<>();

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/reflection/annotations/SupportedAnnotations.java

@@ -194,7 +194,9 @@ public boolean validate(
                 Set<String> ignoredAnnotations) {
             return "LAZY".equals(properties.getEnumValue("fetch"));
         }
-    };
+    },
+
+    KOTLIN(false, "kotlin.Metadata");
 
     private final boolean inherits;
     private final Set<String> partialClassNames;

equalsverifier-core/src/main/java/nl/jqno/equalsverifier/internal/util/Configuration.java

@@ -24,6 +24,7 @@ public final class Configuration<T> {
     private final boolean usingGetClass;
     private final EnumSet<Warning> warningsToSuppress;
     private final Function<String, String> fieldnameToGetter;
+    private final boolean isKotlin;
 
     private final TypeTag typeTag;
     private final AnnotationCache annotationCache;
@@ -46,6 +47,7 @@ private Configuration(
             boolean usingGetClass,
             EnumSet<Warning> warningsToSuppress,
             Function<String, String> fieldnameToGetter,
+            boolean isKotlin,
             List<T> equalExamples,
             List<T> unequalExamples) {
         this.type = type;
@@ -60,6 +62,7 @@ private Configuration(
         this.usingGetClass = usingGetClass;
         this.warningsToSuppress = warningsToSuppress;
         this.fieldnameToGetter = fieldnameToGetter;
+        this.isKotlin = isKotlin;
         this.equalExamples = equalExamples;
         this.unequalExamples = unequalExamples;
     }
@@ -91,6 +94,7 @@ public static <T> Configuration<T> build(
             actualFields);
         Function<String, String> converter =
                 fieldnameToGetter != null ? fieldnameToGetter : DEFAULT_FIELDNAME_TO_GETTER_CONVERTER;
+        boolean isKotlin = annotationCache.hasClassAnnotation(type, SupportedAnnotations.KOTLIN);
 
         return new Configuration<>(type,
                 typeTag,
@@ -104,6 +108,7 @@ public static <T> Configuration<T> build(
                 usingGetClass,
                 warningsToSuppress,
                 converter,
+                isKotlin,
                 equalExamples,
                 unequalExamples);
     }
@@ -200,6 +205,10 @@ public Function<String, String> getFieldnameToGetter() {
         return fieldnameToGetter;
     }
 
+    public boolean isKotlin() {
+        return isKotlin;
+    }
+
     public List<T> getEqualExamples() {
         return Collections.unmodifiableList(equalExamples);
     }

equalsverifier-test-kotlin/pom.xml

@@ -0,0 +1,115 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>nl.jqno.equalsverifier</groupId>
+        <artifactId>equalsverifier-parent</artifactId>
+        <version>3.18.1-SNAPSHOT</version>
+    </parent>
+    <packaging>jar</packaging>
+
+    <artifactId>equalsverifier-test-kotlin</artifactId>
+    <name>EqualsVerifier | test Kotlin</name>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <version>${version.kotlin}</version>
+                <executions>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                        <configuration>
+                            <sourceDirs>
+                                <source>src/main/kotlin</source>
+                            </sourceDirs>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                        <configuration>
+                            <sourceDirs>
+                                <source>src/test/kotlin</source>
+                            </sourceDirs>
+                        </configuration>
+                    </execution>
+                </executions>
+                <configuration>
+                    <jvmTarget>1.8</jvmTarget>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>default-compile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <execution>
+                        <id>default-testCompile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>testCompile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>testCompile</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>
+        <dependency>
+            <groupId>nl.jqno.equalsverifier</groupId>
+            <artifactId>equalsverifier-core</artifactId>
+            <version>${project.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${version.junit-jupiter}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${version.assertj}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib-jdk8</artifactId>
+            <version>${version.kotlin}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-reflect</artifactId>
+            <version>${version.kotlin}</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+</project>

equalsverifier-test-kotlin/src/test/kotlin/nl/jqno/equalsverifier/kotlin/KotlinCompilerGeneratedAnnotationTest.kt

@@ -0,0 +1,31 @@
+package nl.jqno.equalsverifier.kotlin
+
+import nl.jqno.equalsverifier.EqualsVerifier
+import nl.jqno.equalsverifier.internal.reflection.annotations.AnnotationCache
+import nl.jqno.equalsverifier.internal.reflection.annotations.AnnotationCacheBuilder
+import nl.jqno.equalsverifier.internal.reflection.annotations.SupportedAnnotations
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class KotlinCompilerGeneratedAnnotationTest {
+
+  val cache = AnnotationCache()
+  val cacheBuilder = AnnotationCacheBuilder(SupportedAnnotations.values(), HashSet())
+
+  @Test
+  fun `Kotlin classes are recognised as such`() {
+    assertThat(checkAnnotationFor(KotlinClass::class.java)).isTrue()
+  }
+
+  @Test
+  fun `Java classes are not recognised as Kotlin classes`() {
+    assertThat(checkAnnotationFor(EqualsVerifier::class.java)).isFalse()
+  }
+
+  private fun checkAnnotationFor(type: Class<*>): Boolean {
+    cacheBuilder.build(type, cache)
+    return cache.hasClassAnnotation(type, SupportedAnnotations.KOTLIN)
+  }
+}
+
+class KotlinClass