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Add beginnings of pass to transpile/optimize @closureUnaware
This CL just enables constant folding on @closureUnaware code, as a simple way to demo how the pass works. But we will be more thorough about setting CompilerOptions for @closureUnaware in a followup. PiperOrigin-RevId: 845290208
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‎src/com/google/javascript/jscomp/TranspileAndOptimizeClosureUnaware.java‎

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/*
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* Copyright 2025 The Closure Compiler Authors.
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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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* http://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 com.google.javascript.jscomp;
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import static com.google.common.base.Preconditions.checkState;
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import com.google.common.collect.LinkedHashMultimap;
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import com.google.javascript.jscomp.parsing.parser.FeatureSet;
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import com.google.javascript.rhino.Node;
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/**
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* Runs a new Compiler instance over all @closureUnaware code (i.e. "shadow roots") in the AST.
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*
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* <p>This is a separate Compiler instance to avoid leaking compiler state between the shadow AST
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* and main AST. Otherwise, we risk doing unsafe optimizations on @closureUnaware code.
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*/
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class TranspileAndOptimizeClosureUnaware implements CompilerPass {
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private final AbstractCompiler original;
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TranspileAndOptimizeClosureUnaware(AbstractCompiler original) {
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this.original = original;
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}
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@Override
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public void process(Node externs, Node root) {
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var collector = new CollectShadowAsts();
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NodeTraversal.traverse(original, root, collector);
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if (collector.shadowAsts.isEmpty()) {
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return;
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}
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var shadowOptions = new CompilerOptions();
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// TODO: b/421971366 - enable simple optimizations + debugging options + transpilation
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shadowOptions.setFoldConstants(true);
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// TODO: b/421971366 - enable configuring Mode.TRANSPILE_ONLY.
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NestedCompilerRunner shadowCompiler =
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NestedCompilerRunner.create(
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original, shadowOptions, NestedCompilerRunner.Mode.TRANSPILE_AND_OPTIMIZE);
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initShadowInputs(shadowCompiler, collector.shadowAsts);
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shadowCompiler.compile();
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reattachShadowNodes(collector.shadowAsts);
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}
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private record ShadowAst(Node originalRoot, Node callNode, Node script) {}
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/** Traverses all closure unaware SCRIPTs to collect shadow ASTs. */
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private static final class CollectShadowAsts implements NodeTraversal.Callback {
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private final LinkedHashMultimap<SourceFile, ShadowAst> shadowAsts =
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LinkedHashMultimap.create();
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@Override
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public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
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if (!n.isScript()) {
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return true;
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}
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return n.isClosureUnawareCode();
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}
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@Override
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public void visit(NodeTraversal t, Node n, Node parent) {
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Node shadow = n.getClosureUnawareShadow();
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if (shadow == null) {
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return;
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}
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// CALL
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// GETPROP .call
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// NAME $jscomp_wrap_closure_unaware_code
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// NAME globalThis
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// or
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// CALL
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// GETPROP .call
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// NAME $jscomp_wrap_closure_unaware_code
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// NAME undefined
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// or
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// CALL
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// NAME $jscomp_wrap_closure_unaware_code
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Node callNode = n.getParent().isCall() ? n.getParent() : n.getGrandparent();
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checkState(callNode.isCall(), callNode);
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shadowAsts.put(
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t.getInput().getSourceFile(), new ShadowAst(shadow, callNode, shadow.getOnlyChild()));
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}
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}
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private void initShadowInputs(
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NestedCompilerRunner shadowCompiler,
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LinkedHashMultimap<SourceFile, ShadowAst> perFileInputs) {
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for (SourceFile sourceFile : perFileInputs.keySet()) {
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int indexInFile = 0;
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for (ShadowAst shadowAst : perFileInputs.get(sourceFile)) {
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String uniqueName = sourceFile.getName() + ".shadow" + indexInFile++;
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shadowCompiler.addScript(shadowAst.script().detach(), uniqueName);
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// TODO: b/421971366 - attach the correct FeatureSet, either here or possibly during
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// parsing.
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shadowAst.script().putProp(Node.FEATURE_SET, FeatureSet.BARE_MINIMUM);
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}
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}
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}
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/**
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* Re-attaches the shadow AST scripts, that were previously detached for compilation, to their
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* associated ROOT nodes from the main AST.
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*/
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private void reattachShadowNodes(LinkedHashMultimap<SourceFile, ShadowAst> inputs) {
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for (ShadowAst shadowAst : inputs.values()) {
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Node script = shadowAst.script();
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checkState(script.hasOneChild(), script.toStringTree());
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shadowAst.originalRoot().addChildToFront(script.detach());
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// Remove traces of the shadow compilation.
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script.setInputId(null);
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script.setStaticSourceFile(null);
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}
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}
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}

‎test/com/google/javascript/jscomp/TranspileAndOptimizeClosureUnawareTest.java‎

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/*
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* Copyright 2025 The Closure Compiler Authors.
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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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* http://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 com.google.javascript.jscomp;
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import static com.google.javascript.jscomp.CompilerTestCase.srcs;
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import com.google.javascript.rhino.Node;
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import org.junit.Before;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.junit.runners.JUnit4;
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@RunWith(JUnit4.class)
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public class TranspileAndOptimizeClosureUnawareTest extends CompilerTestCase {
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@Override
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protected CompilerPass getProcessor(Compiler compiler) {
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return this::process;
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}
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private void process(Node externs, Node root) {
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Compiler compiler = getLastCompiler();
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ManageClosureUnawareCode.wrap(compiler).process(externs, root);
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new TranspileAndOptimizeClosureUnaware(compiler).process(externs, root);
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ManageClosureUnawareCode.unwrap(compiler).process(externs, root);
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}
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private int inputCount;
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private int outputCount;
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@Before
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public void setup() {
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disableValidateAstChangeMarking();
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allowExternsChanges();
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this.inputCount = 0;
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this.outputCount = 0;
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}
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String createPrettyPrinter(Node n) {
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return new CodePrinter.Builder(n)
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.setCompilerOptions(getLastCompiler().getOptions())
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.setPrettyPrint(true)
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.build();
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}
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@Test
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public void testEmptyClosureUnawareFn_unchanged() {
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test(srcs(closureUnaware("")), expected(expectedClosureUnaware("")));
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}
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@Test
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public void testFoldConstants() {
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test(
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srcs(closureUnaware("console.log(1 + 2);")),
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expected(expectedClosureUnaware("console.log(3);")));
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}
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@Test
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public void testFoldConstants_multipleFiles() {
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test(
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srcs(
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closureUnaware("console.log(1 + 2);"),
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closureUnaware("console.log(11 + 22);"),
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closureUnaware("console.log(111 + 222);")),
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expected(
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expectedClosureUnaware("console.log(3);"),
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expectedClosureUnaware("console.log(33);"),
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expectedClosureUnaware("console.log(333);")));
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}
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@Test
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public void testFoldConstants_multipleFiles_ignoresNonClosureUnaware() {
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test(
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srcs(
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closureUnaware("console.log(1 + 2);"),
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"""
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goog.module('some.other.file');
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console.log(11 + 22);
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"""),
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expected(
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expectedClosureUnaware("console.log(3);"),
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"""
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goog.module('some.other.file');
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console.log(11 + 22);
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"""));
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}
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@Test
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public void testFoldConstants_multipleClosureUnawareBlocksInFile() {
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test(
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srcs(
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closureUnaware(
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"console.log(1 + 2);", "console.log(11 + 22);", "console.log(111 + 222);")),
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expected(
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expectedClosureUnaware("console.log(3);", "console.log(33);", "console.log(333);")));
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}
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private String closureUnaware(String... closureUnaware) {
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String prefix =
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String.format(
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"""
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/** @fileoverview @closureUnaware */
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goog.module('test%d');
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""",
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inputCount++);
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StringBuilder input = new StringBuilder().append(prefix);
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for (String block : closureUnaware) {
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input.append(
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String.format(
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"""
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/** @closureUnaware */
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(function() {
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%s
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}).call(undefined);
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""",
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block));
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}
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return input.toString();
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}
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@Test
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public void testFoldConstants_directCallInsteadOfDotCall() {
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test(
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srcs(
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// Don't use the "closureUnaware()" wrapper because it always uses .call - we want to
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// specifically test a regular direct call.
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"""
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/** @fileoverview @closureUnaware */
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goog.module('test');
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/** @closureUnaware */
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(function() {
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console.log(1 + 2);
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})();
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"""),
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expected(
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"""
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/** @fileoverview @closureUnaware */
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goog.module('test');
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(function() {
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console.log(3);
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})();
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"""));
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}
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private String expectedClosureUnaware(String... closureUnaware) {
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String prefix =
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String.format(
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"""
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/** @fileoverview @closureUnaware */
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goog.module('test%d');
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""",
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outputCount++);
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StringBuilder output = new StringBuilder().append(prefix);
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for (String block : closureUnaware) {
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output.append(
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String.format(
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"""
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(function() {
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%s
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}).call(undefined);
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""",
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block));
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}
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return output.toString();
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}
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// TODO: b/421971366 - add a greater variety of test cases.
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}

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