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Add Object.toMixin() method
Adds a toMixin() method to the Object class that converts an Object into a Mixin function applicable via the pipe operator (|>). A generic toMixin() method cannot be implemented in user land, so this implementation provides a native method that properly handles: - Property merging and overriding - Element appending with correct index offsetting - Entry merging with proper key handling - Nested object replacement vs amendment semantics Implementation uses the source Object's enclosing frame to ensure proper module context for type resolution during member evaluation.
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‎pkl-core/src/main/java/org/pkl/core/stdlib/base/ObjectNodes.java‎

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/*
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* Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.pkl.core.stdlib.base;
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import com.oracle.truffle.api.CompilerDirectives;
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import com.oracle.truffle.api.dsl.Specialization;
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import com.oracle.truffle.api.frame.FrameDescriptor;
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import com.oracle.truffle.api.frame.VirtualFrame;
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import org.pkl.core.ast.member.ObjectMember;
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import org.pkl.core.runtime.*;
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import org.pkl.core.stdlib.ExternalMethod0Node;
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public final class ObjectNodes {
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private ObjectNodes() {}
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public abstract static class toMixin extends ExternalMethod0Node {
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@Specialization
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protected VmFunction eval(VmObject self) {
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CompilerDirectives.transferToInterpreterAndInvalidate();
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var rootNode = new ObjectToMixinRootNode(self, new FrameDescriptor());
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return new VmFunction(
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VmUtils.createEmptyMaterializedFrame(),
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null,
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1,
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rootNode,
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null);
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}
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}
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private static final class ObjectToMixinRootNode extends org.pkl.core.ast.PklRootNode {
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private final VmObject sourceObject;
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public ObjectToMixinRootNode(VmObject sourceObject, FrameDescriptor descriptor) {
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super(null, descriptor);
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this.sourceObject = sourceObject;
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}
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@Override
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public com.oracle.truffle.api.source.SourceSection getSourceSection() {
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return VmUtils.unavailableSourceSection();
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}
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@Override
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public String getName() {
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return "toMixin";
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}
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@Override
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protected Object executeImpl(VirtualFrame frame) {
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var arguments = frame.getArguments();
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if (arguments.length != 3) {
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CompilerDirectives.transferToInterpreter();
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throw new VmExceptionBuilder()
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.evalError("wrongFunctionArgumentCount", 1, arguments.length - 2)
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.build();
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}
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var targetObject = arguments[2];
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if (!(targetObject instanceof VmObject)) {
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CompilerDirectives.transferToInterpreter();
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throw new VmExceptionBuilder()
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.typeMismatch(targetObject, BaseModule.getDynamicClass())
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.build();
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}
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var parent = (VmObject) targetObject;
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var parentLength = (parent instanceof VmDynamic) ? ((VmDynamic) parent).getLength() : 0;
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var sourceLength = (sourceObject instanceof VmDynamic) ? ((VmDynamic) sourceObject).getLength() : 0;
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var adjustedMembers = adjustMemberIndices(sourceObject.getMembers(), parentLength);
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return new VmDynamic(
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sourceObject.getEnclosingFrame(),
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parent,
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adjustedMembers,
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parentLength + sourceLength);
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}
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// Adjust element indices in the members map by offsetting them by parentLength
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@CompilerDirectives.TruffleBoundary
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private static org.graalvm.collections.UnmodifiableEconomicMap<Object, ObjectMember> adjustMemberIndices(
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org.graalvm.collections.UnmodifiableEconomicMap<Object, ObjectMember> members,
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long parentLength) {
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if (parentLength == 0) {
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return members;
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}
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var result = org.pkl.core.util.EconomicMaps.<Object, ObjectMember>create(
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org.pkl.core.util.EconomicMaps.size(members));
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var cursor = members.getEntries();
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while (cursor.advance()) {
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var key = cursor.getKey();
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var member = cursor.getValue();
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// If this is an element (not an entry with an Int key), offset the index
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if (member.isElement()) {
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// Elements always have Long keys
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var newKey = (Long) key + parentLength;
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org.pkl.core.util.EconomicMaps.put(result, newKey, member);
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} else {
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// Properties and entries are not offset
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org.pkl.core.util.EconomicMaps.put(result, key, member);
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}
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}
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return result;
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}
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}
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}

‎pkl-core/src/test/files/LanguageSnippetTests/input/api/objectToMixin.pkl‎

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amends "../snippetTest.pkl"
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local class Person {
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name: String
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age: Int = 0
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}
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open local class Animal {
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name: String
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age: Int
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}
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local class Dog extends Animal {
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breed: String = "Unknown"
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}
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local class Config {
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port: Int(isBetween(1, 65535))
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}
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local class ServerConfig {
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host: String
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port: Int
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}
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local class Settings {
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enabled: Boolean = true
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timeout: Int = 30
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}
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examples {
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["basic conversion"] {
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// Convert Dynamic with properties to Mixin
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local dynamic1 = new Dynamic {
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name = "Pigeon"
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age = 42
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}
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local mixin1 = dynamic1.toMixin()
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new Dynamic { name = "Original" } |> mixin1
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}
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["empty Dynamic"] {
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// Empty Dynamic should create identity mixin
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local emptyDynamic = new Dynamic {}
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local emptyMixin = emptyDynamic.toMixin()
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new Dynamic { existing = "value" } |> emptyMixin
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}
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["with elements"] {
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// Elements should be appended
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local dynamicWithElements = new Dynamic {
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"element1"
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"element2"
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}
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local mixinWithElements = dynamicWithElements.toMixin()
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new Dynamic { "base" } |> mixinWithElements
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}
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["with entries"] {
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// Entries should be merged
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local dynamicWithEntries = new Dynamic {
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["key1"] = "value1"
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["key2"] = "value2"
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}
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local mixinWithEntries = dynamicWithEntries.toMixin()
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new Dynamic { ["baseKey"] = "baseValue" } |> mixinWithEntries
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}
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["with mixed members"] {
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// Properties, elements, and entries should all be merged
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local dynamicMixed = new Dynamic {
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prop = "property"
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"element"
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["entry"] = "entryValue"
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}
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local mixinMixed = dynamicMixed.toMixin()
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new Dynamic { baseProp = "base" } |> mixinMixed
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}
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["applying to Typed object"] {
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// Mixin should work with typed objects
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local dynamicPerson = new Dynamic {
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name = "Modified"
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age = 100
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}
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local mixinPerson = dynamicPerson.toMixin()
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new Person { name = "Original"; age = 20 } |> mixinPerson
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}
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["chaining mixins"] {
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// Multiple mixins can be chained
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local mixin1 = new Dynamic { extra = "value" }.toMixin()
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local mixin2 = new Dynamic { another = "field" }.toMixin()
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new Dynamic { base = "start" } |> mixin1 |> mixin2
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}
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["reusable mixin"] {
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// Mixin can be applied to multiple objects
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local reusableMixin = new Dynamic { shared = "config" }.toMixin()
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new {
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first = new Dynamic { id = 1 } |> reusableMixin
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second = new Dynamic { id = 2 } |> reusableMixin
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}
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}
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["overriding properties"] {
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// Properties from mixin should override base properties
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local overrideDynamic = new Dynamic {
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name = "Override"
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value = 999
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}
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local overrideMixin = overrideDynamic.toMixin()
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new Dynamic { name = "Original"; value = 1; other = "keep" } |> overrideMixin
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}
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["replacement vs merge for nested objects"] {
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// Test replacement vs merge semantics
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local base = new {
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a1 {
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b1 = 2
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}
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a2 {
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b1 = 2
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}
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}
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local overrideValue = new Dynamic {
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a1 = new Dynamic {
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b2 = 2
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}
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a2 {
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b2 = 2
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}
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}
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(base) |> overrideValue.toMixin()
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}
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["integer entry keys vs elements"] {
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// CRITICAL: Test that integer entry keys are NOT offset like elements
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// This tests the fix for using member.isElement() instead of key instanceof Long
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local mixinWithIntKeys = new Dynamic {
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[5] = "entry at 5"
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[10] = "entry at 10"
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"element0"
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"element1"
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}.toMixin()
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new Dynamic {
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"base0"
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"base1"
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[99] = "base entry at 99"
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} |> mixinWithIntKeys
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}
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["class hierarchy"] {
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// Test with class inheritance
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local mixin = new Dynamic {
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age = 5
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breed = "Labrador"
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}.toMixin()
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new Dog { name = "Buddy"; age = 3 } |> mixin
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}
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["constraints are preserved"] {
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// Mixin should preserve constraints from base object
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local mixin = new Dynamic { port = 8080 }.toMixin()
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new Config { port = 3000 } |> mixin
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}
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["local members are not exposed"] {
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// Local members in mixin source should not appear in result
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local source = new Dynamic {
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local helper = "should not appear"
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visible = "should appear"
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}
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new Dynamic { base = "value" } |> source.toMixin()
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}
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["nested amendment semantics"] {
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// Deep nesting with amendments should work correctly
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local mixin = new Dynamic {
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outerVal {
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inner = new Dynamic {
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deep = "value"
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}
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}
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}.toMixin()
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new Dynamic {
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outerVal {
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inner = new Dynamic {
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shallow = "base"
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}
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sibling = "data"
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}
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} |> mixin
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}
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["typed object to mixin"] {
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// Non-Dynamic typed objects can also be converted to mixins
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local config = new ServerConfig {
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host = "localhost"
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port = 8080
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}
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new Dynamic { existing = "field" } |> config.toMixin()
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}
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["mixin from typed class with defaults"] {
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// Test that default values work correctly
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local mixin = new Settings { enabled = false }.toMixin()
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new Dynamic { custom = "value" } |> mixin
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}
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["element index offset with gaps"] {
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// Elements should be offset correctly even with gaps in parent
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local mixin = new Dynamic {
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"mixinElement0"
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"mixinElement1"
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}.toMixin()
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new Dynamic {
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"base0"
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"base1"
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"base2"
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} |> mixin
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}
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["empty parent with mixin elements"] {
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// Elements should start at 0 when parent has no elements
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local mixin = new Dynamic {
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"elem0"
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"elem1"
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}.toMixin()
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new Dynamic { prop = "value" } |> mixin
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}
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["mixin self application"] {
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// Applying mixin derived from an object to itself
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local obj = new Dynamic { count = 1 }
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local mixin = obj.toMixin()
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obj |> mixin
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}
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}

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