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google / closure-compiler

A JavaScript checker and optimizer.
https://developers.google.com/closure/compiler/
Apache License 2.0
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NullPointerException if --process_common_js_modules is paired with exports variable messing #2613

Open etki opened 7 years ago

etki commented 7 years ago

Given file proof.js

var exports = {}

function itFails (name) {
  exports[name] = 'anything'
}

module.exports = exports

and following command against v2017-06-26

java -jar closure-compiler.jar --process_common_js_modules --js proof.js

I hit a NPE

proof.js:1: WARNING - Suspicious re-assignment of "exports" variable. Did you actually intend to export something?
var exports = {}
    ^^^^^^^^^^^^

0 error(s), 1 warning(s)
java.lang.RuntimeException: INTERNAL COMPILER ERROR.
Please report this problem.

null
  Node(NAME name): proof.js:4:10
  exports[name] = 'anything'
  Parent(GETELEM): proof.js:4:2
  exports[name] = 'anything'

        at com.google.javascript.jscomp.NodeUtil.getRValueOfLValue(NodeUtil.java:4549)
        at com.google.javascript.jscomp.ProcessCommonJSModules$RewriteModule.getExportedName(ProcessCommonJSModules.java:1136)
        at com.google.javascript.jscomp.ProcessCommonJSModules$RewriteModule.maybeUpdateName(ProcessCommonJSModules.java:936)
        at com.google.javascript.jscomp.ProcessCommonJSModules$RewriteModule.visit(ProcessCommonJSModules.java:712)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:730)
        at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
        at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
        at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:726)
        at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
        at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:817)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:724)
        at com.google.javascript.jscomp.NodeTraversal.traverseFunction(NodeTraversal.java:761)
        at com.google.javascript.jscomp.NodeTraversal.handleFunction(NodeTraversal.java:692)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:708)
        at com.google.javascript.jscomp.NodeTraversal.traverseChildren(NodeTraversal.java:802)
        at com.google.javascript.jscomp.NodeTraversal.handleScript(NodeTraversal.java:680)
        at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:705)
        at com.google.javascript.jscomp.NodeTraversal.traverse(NodeTraversal.java:307)
        at com.google.javascript.jscomp.NodeTraversal.traverseEs6(NodeTraversal.java:647)
        at com.google.javascript.jscomp.ProcessCommonJSModules.process(ProcessCommonJSModules.java:134)
        at com.google.javascript.jscomp.Compiler.processAMDAndCommonJSModules(Compiler.java:2106)
        at com.google.javascript.jscomp.Compiler.parseInputs(Compiler.java:1792)
        at com.google.javascript.jscomp.Compiler.parseForCompilationInternal(Compiler.java:994)
        at com.google.javascript.jscomp.Compiler.access$300(Compiler.java:102)
        at com.google.javascript.jscomp.Compiler$6.call(Compiler.java:974)
        at com.google.javascript.jscomp.Compiler$6.call(Compiler.java:971)
        at com.google.javascript.jscomp.CompilerExecutor$2.call(CompilerExecutor.java:93)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
        ... 34 more

(i do understand that provided code doesn't comply to CommonJS module expectations, i'm just reporting an error as i was asked by output)

ray007 commented 6 years ago

Name the variable something other than exports

brad4d commented 6 years ago

@etki thanks for following the instructions and reporting this issue. This is a low priority to fix, though, since the output also points out that the input source code was incorrectly trying to redeclare exports.

It's also possible that the problem has been fixed since you reported it, but I don't have time right now to check.