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anivaranivar
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Implement ES2025 Iterator helper methods
Adds Iterator.prototype methods per TC39 iterator helpers proposal: Transformation methods: - map(mapperFn) - Transform each value - filter(predicateFn) - Filter values - flatMap(mapperFn) - Map and flatten Limiting methods: - take(limit) - Take first N values - drop(limit) - Skip first N values Consumption methods: - toArray() - Collect to array - reduce(reducerFn, initialValue) - Reduce values - forEach(callbackFn) - Iterate with callback Testing methods: - some(predicateFn) - Test if any match - every(predicateFn) - Test if all match - find(predicateFn) - Find first matching value Static method: - Iterator.from(obj) - Create iterator from iterable or iterator-like Implementation follows 2025 Rhino architecture patterns: - JSCode architecture for stateful, resumable execution - Context safety: Context always passed as parameter, never captured - BaseFunction-based constructor (not callable/constructable per spec) - Factory pattern for clean helper method organization - Full serialization support for cross-context caching Integration: - Enabled via Context.VERSION_ECMASCRIPT for backwards compatibility - Coexists with legacy Iterator (pre-ES2025) for older language versions - Integrates with upstream's lambda-based NativeIterator (commit ad0dd02) - Preserves StopIteration for generator compatibility Addresses reviewer feedback: - @gbrail (Sept 16): Uses VERSION_ECMASCRIPT instead of feature flag - @rbri (Oct 13): Clean PR with proper test262.properties
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‎rhino/src/main/java/org/mozilla/javascript/ES2025IteratorOperations.java‎

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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mozilla.javascript;
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/**
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* Simple Iterator helper implementations for ES2025 Iterator methods. Groups basic transformation
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* and filtering operations in one file for maintainability. Uses aardvark179's JSCode architecture
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* for Context safety.
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*/
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public final class ES2025IteratorOperations {
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private ES2025IteratorOperations() {
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// Utility class - no instances
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}
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/**
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* JSCode implementation for Iterator.prototype.map(). Transforms each value from the source
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* iterator using a mapping function.
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*/
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public static class MapCode extends IteratorHelperCode {
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public MapCode(
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Scriptable sourceIterator, Function mapperFunction, Scriptable mapperThisArg) {
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super(sourceIterator, mapperFunction, mapperThisArg);
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}
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@Override
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protected Object processNext(
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Context cx, JSFunction fn, Scriptable scope, int operation, Object value) {
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// Get next value from source iterator
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Object sourceValue = getNextFromSource(cx, scope);
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if (sourceValue == null) {
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// Source iterator is exhausted
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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// Apply the mapping function with fresh Context
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Object mappedValue = callHelperFunction(cx, scope, sourceValue);
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currentIndex++;
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// Return the mapped value
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return createIteratorResult(cx, scope, mappedValue, false);
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}
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}
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/**
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* JSCode implementation for Iterator.prototype.filter(). Filters values from the source
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* iterator using a predicate function.
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*/
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public static class FilterCode extends IteratorHelperCode {
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public FilterCode(
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Scriptable sourceIterator,
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Function predicateFunction,
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Scriptable predicateThisArg) {
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super(sourceIterator, predicateFunction, predicateThisArg);
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}
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@Override
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protected Object processNext(
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Context cx, JSFunction fn, Scriptable scope, int operation, Object value) {
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while (true) {
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// Get next value from source iterator
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Object sourceValue = getNextFromSource(cx, scope);
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if (sourceValue == null) {
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// Source iterator is exhausted
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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// Test the predicate with fresh Context
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Object testResult = callHelperFunction(cx, scope, sourceValue);
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currentIndex++;
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// If predicate passes, return this value
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if (ScriptRuntime.toBoolean(testResult)) {
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return createIteratorResult(cx, scope, sourceValue, false);
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}
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// Otherwise, continue to next value
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}
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}
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}
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/**
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* JSCode implementation for Iterator.prototype.take(). Limits the number of values from the
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* source iterator.
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*/
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public static class TakeCode extends IteratorHelperCode {
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private final long limit;
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private long taken = 0;
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// Static factory method for proper limit handling
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public static TakeCode create(Scriptable sourceIterator, long limit) {
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return new TakeCode(sourceIterator, limit);
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}
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private TakeCode(Scriptable sourceIterator, long limit) {
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super(sourceIterator, null, null);
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this.limit = limit;
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}
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@Override
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protected Object processNext(
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Context cx, JSFunction fn, Scriptable scope, int operation, Object value) {
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// Check if we've reached the limit
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if (taken >= limit) {
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isExhausted = true;
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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// Get next value from source iterator
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Object sourceValue = getNextFromSource(cx, scope);
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if (sourceValue == null) {
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// Source iterator is exhausted
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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taken++;
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currentIndex++;
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return createIteratorResult(cx, scope, sourceValue, false);
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}
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}
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/**
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* JSCode implementation for Iterator.prototype.drop(). Skips the first N values from the source
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* iterator.
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*/
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public static class DropCode extends IteratorHelperCode {
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private final long limit;
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private long dropped = 0;
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private boolean skipPhaseComplete = false;
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// Static factory method for proper limit handling
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public static DropCode create(Scriptable sourceIterator, long limit) {
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return new DropCode(sourceIterator, limit);
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}
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private DropCode(Scriptable sourceIterator, long limit) {
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super(sourceIterator, null, null);
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this.limit = limit;
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}
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@Override
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protected Object processNext(
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Context cx, JSFunction fn, Scriptable scope, int operation, Object value) {
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// Skip the first 'limit' values
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while (!skipPhaseComplete && dropped < limit) {
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Object sourceValue = getNextFromSource(cx, scope);
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if (sourceValue == null) {
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// Source iterator exhausted during skip phase
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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dropped++;
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}
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skipPhaseComplete = true;
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// Now return values normally
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Object sourceValue = getNextFromSource(cx, scope);
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if (sourceValue == null) {
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// Source iterator is exhausted
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return createIteratorResult(cx, scope, Undefined.instance, true);
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}
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currentIndex++;
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return createIteratorResult(cx, scope, sourceValue, false);
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}
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}
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}

‎rhino/src/main/java/org/mozilla/javascript/ES6IteratorAdapter.java‎

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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mozilla.javascript;
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/**
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* Wrapper for iterators returned by Iterator.from(). This class wraps any iterator and ensures it
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* inherits from Iterator.prototype while delegating all operations to the wrapped iterator.
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*/
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public final class ES6IteratorAdapter extends ScriptableObject {
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private static final long serialVersionUID = 1L;
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private Scriptable wrappedIterator;
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public ES6IteratorAdapter(Scriptable wrappedIterator, Scriptable scope) {
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this.wrappedIterator = wrappedIterator;
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// Set parent scope
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setParentScope(scope);
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// Set prototype to inherit from Iterator.prototype if available
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Scriptable iteratorPrototype = NativeIteratorConstructor.getIteratorPrototype(scope);
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if (iteratorPrototype != null) {
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setPrototype(iteratorPrototype);
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}
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}
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@Override
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public String getClassName() {
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return "Iterator";
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}
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@Override
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public Object get(String name, Scriptable start) {
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// Special handling for 'next' method - create a bound version
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if ("next".equals(name) && wrappedIterator != null) {
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Object nextMethod = ScriptableObject.getProperty(wrappedIterator, "next");
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if (nextMethod instanceof Callable) {
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// Return a function that calls next() with the wrapped iterator as 'this'
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return new BaseFunction() {
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@Override
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public Object call(
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Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
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return ((Callable) nextMethod).call(cx, scope, wrappedIterator, args);
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}
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@Override
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public String getFunctionName() {
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return "next";
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}
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};
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}
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}
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// Special handling for 'return' method
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if ("return".equals(name) && wrappedIterator != null) {
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Object returnMethod = ScriptableObject.getProperty(wrappedIterator, "return");
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if (returnMethod instanceof Callable) {
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return new BaseFunction() {
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@Override
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public Object call(
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Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
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return ((Callable) returnMethod).call(cx, scope, wrappedIterator, args);
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}
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@Override
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public String getFunctionName() {
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return "return";
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}
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};
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}
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}
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// Delegate other properties to wrapped iterator
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if (wrappedIterator != null) {
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Object value = ScriptableObject.getProperty(wrappedIterator, name);
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if (value != Scriptable.NOT_FOUND) {
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return value;
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}
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}
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// Fall back to our prototype chain
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return super.get(name, start);
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}
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@Override
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public Object get(int index, Scriptable start) {
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if (wrappedIterator != null) {
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Object value = wrappedIterator.get(index, wrappedIterator);
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if (value != Scriptable.NOT_FOUND) {
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return value;
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}
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}
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return super.get(index, start);
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}
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@Override
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public boolean has(String name, Scriptable start) {
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if (wrappedIterator != null) {
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// Check if property exists in wrapped iterator or its prototype chain
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Object value = ScriptableObject.getProperty(wrappedIterator, name);
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if (value != Scriptable.NOT_FOUND) {
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return true;
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}
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}
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return super.has(name, start);
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}
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@Override
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public boolean has(int index, Scriptable start) {
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if (wrappedIterator != null && wrappedIterator.has(index, wrappedIterator)) {
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return true;
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}
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return super.has(index, start);
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}
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@Override
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public void put(String name, Scriptable start, Object value) {
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if (wrappedIterator != null) {
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wrappedIterator.put(name, wrappedIterator, value);
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} else {
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super.put(name, start, value);
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}
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}
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@Override
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public void put(int index, Scriptable start, Object value) {
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if (wrappedIterator != null) {
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wrappedIterator.put(index, wrappedIterator, value);
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} else {
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super.put(index, start, value);
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}
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}
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@Override
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public void delete(String name) {
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if (wrappedIterator != null) {
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wrappedIterator.delete(name);
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} else {
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super.delete(name);
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}
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}
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@Override
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public void delete(int index) {
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if (wrappedIterator != null) {
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wrappedIterator.delete(index);
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} else {
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super.delete(index);
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}
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}
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@Override
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public Object[] getIds() {
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if (wrappedIterator != null) {
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return wrappedIterator.getIds();
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}
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return super.getIds();
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}
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}

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