Add Kotlin implementation for NullabilityDetector

KotlinNullabilityDetector relies on Kotlin Metadata to detect parameter
nullability.

rhino-kotlin/build.gradle

@@ -0,0 +1,41 @@
+plugins {
+    id 'rhino.library-conventions'
+}
+
+dependencies {
+    implementation project(':rhino-reflection')
+    implementation 'org.jetbrains.kotlin:kotlin-metadata-jvm:2.1.0'
+}
+
+publishing {
+    publications {
+        rhinokotlin(MavenPublication) {
+            from components.java
+            artifacts = [jar, sourceJar]
+            pom.withXml {
+                def root = asNode()
+
+                root.appendNode('description', "Rhino reflection interfaces implementations for Kotlin")
+                root.appendNode("url", "https://mozilla.github.io/rhino/")
+
+                def p = root.appendNode("parent")
+                p.appendNode("groupId", "org.sonatype.oss")
+                p.appendNode("artifactId", "oss-parent")
+                p.appendNode("version", "7")
+
+                def l = root.appendNode("licenses").appendNode("license")
+                l.appendNode("name", "Mozilla Public License, Version 2.0")
+                l.appendNode("url", "http://www.mozilla.org/MPL/2.0/index.txt")
+
+                def scm = root.appendNode("scm")
+                scm.appendNode("connection", "scm:git:[email protected]:mozilla/rhino.git")
+                scm.appendNode("developerConnection", "scm:git:[email protected]:mozilla/rhino.git")
+                scm.appendNode("url", "[email protected]:mozilla/rhino.git")
+
+                def o = root.appendNode("organization")
+                o.appendNode("name", "The Mozilla Foundation")
+                o.appendNode("url", "http://www.mozilla.org")
+            }
+        }
+    }
+}

rhino-kotlin/src/main/java/module-info.java

@@ -0,0 +1,11 @@
+import org.mozilla.javascript.reflection.NullabilityDetector;
+import org.mozilla.kotlin.KotlinNullabilityDetector;
+
+module org.mozilla.rhino.kotlin {
+    requires kotlin.metadata.jvm;
+    requires kotlin.stdlib;
+    requires org.mozilla.javascript.reflection;
+
+    provides NullabilityDetector with
+            KotlinNullabilityDetector;
+}

rhino-kotlin/src/main/java/org/mozilla/kotlin/KotlinNullabilityDetector.java

@@ -0,0 +1,60 @@
+package org.mozilla.kotlin;
+
+import static kotlin.metadata.Attributes.isNullable;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.Optional;
+import kotlin.Metadata;
+import kotlin.metadata.KmClass;
+import kotlin.metadata.KmFunction;
+import kotlin.metadata.KmValueParameter;
+import kotlin.metadata.jvm.KotlinClassMetadata;
+import org.mozilla.javascript.reflection.NullabilityDetector;
+
+public class KotlinNullabilityDetector implements NullabilityDetector {
+    @Override
+    public boolean[] getParameterNullability(Method method) {
+        boolean[] result = new boolean[method.getParameterTypes().length];
+        Metadata metadata = method.getDeclaringClass().getAnnotation(Metadata.class);
+        if (metadata != null) {
+            result = getParameterNullabilityFromKotlinMetadata(metadata, method.getName(), result);
+        }
+        return result;
+    }
+
+    @Override
+    public boolean[] getParameterNullability(Constructor<?> constructor) {
+        boolean[] result = new boolean[constructor.getParameterTypes().length];
+        Metadata metadata = constructor.getDeclaringClass().getAnnotation(Metadata.class);
+        if (metadata != null) {
+            result =
+                    getParameterNullabilityFromKotlinMetadata(
+                            metadata, constructor.getName(), result);
+        }
+        return result;
+    }
+
+    private boolean[] getParameterNullabilityFromKotlinMetadata(
+            Metadata metadata, String methodName, boolean[] fallback) {
+        KotlinClassMetadata.Class kMetadata =
+                (KotlinClassMetadata.Class) KotlinClassMetadata.readLenient(metadata);
+        KmClass clazz = kMetadata.getKmClass();
+        Optional<KmFunction> function =
+                clazz.getFunctions().stream()
+                        .filter(f -> f.getName().equals(methodName))
+                        .findFirst();
+        if (function.isPresent()) {
+            List<KmValueParameter> params = function.get().getValueParameters();
+            boolean[] result = new boolean[params.size()];
+            int index = 0;
+            for (KmValueParameter parameter : params) {
+                result[index++] = isNullable(parameter.getType());
+            }
+            return result;
+        } else {
+            return fallback;
+        }
+    }
+}

rhino-kotlin/src/main/resources/META-INF/services/org.mozilla.javascript.reflection.NullabilityDetector

@@ -0,0 +1 @@
+org.mozilla.kotlin.KotlinNullabilityDetector

settings.gradle

@@ -1,4 +1,4 @@
 rootProject.name = 'rhino-root'
 include 'rhino', 'rhino-engine', 'rhino-tools', 'rhino-xml', 'rhino-all', 'examples', 'testutils', 'tests', 'benchmarks'
-include 'rhino-reflection'
+include 'rhino-reflection', 'rhino-kotlin'