Uglifyjs: Latest 3.1.7 gives error with webpack uglify plugin

[bkniffler]

Sorry, I don't have too much detail, I've got quite a complex project where I use uglifyjs-webpack-plugin. Today I wanted to build my project and got this error:

Error in {chunk name}.js from Uglifyjs.
undefined

Nothing more, no helpful output whatsoever. I noticed there was a new version of uglifyjs and when I forced 3.1.6, the error was gone.

[alexlamsl]

Closing for now - please report back if you have more actionable details.

[modosc]

fwiw i see the same behavior - not sure exactly where to start with this since the error doesn't give any context.

[kzc]

File a bug report with uglifyjs-webpack-plugin to print out the uglify minify() error.

[Jessidhia]

This is a problem that happens when parallel: true is enabled, because the Error object is lost when it is sent across Worker boundaries. Use parallel: false to see the actual error, which is:

ERROR in bundle.a32a8a2e8d54ecb71de3.js from UglifyJs
RangeError: Maximum call stack size exceeded
    at new AST_SymbolRef (eval at DEFNODE (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1)), <anonymous>:2:30)
    at AST_SymbolRef._clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:462:16)
    at AST_SymbolRef.clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:465:21)
    at AST_SymbolRef._clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:455:29)
    at AST_SymbolRef.clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:465:21)
    at TreeTransformer.eval [as before] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:458:33)
    at AST_SymbolRef.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4558:35)
    at eval (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4678:43)
    at AST_Call.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4562:21)
    at AST_Call._clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:456:25)
    at AST_Call.clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:465:21)
    at TreeTransformer.eval [as before] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:458:33)
    at AST_Call.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4558:35)
    at eval (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4589:31)
    at AST_SimpleStatement.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4562:21)
    at AST_SimpleStatement._clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:456:25)
    at AST_SimpleStatement.clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:465:21)
    at TreeTransformer.eval [as before] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:458:33)
    at AST_SimpleStatement.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4558:35)
    at eval (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4577:25)
    at doit (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:134:23)
    at MAP (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:160:52)
    at do_list (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4576:16)
    at eval (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4673:25)
    at AST_Function.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4562:21)
    at AST_Function._clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:456:25)
    at AST_Function.clone (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:465:21)
    at TreeTransformer.eval [as before] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:458:33)
    at AST_Function.eval [as transform] (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4558:35)
    at eval (eval at <anonymous> (.../node_modules/uglify-es/tools/node.js:21:1), <anonymous>:4687:43)

[kzc]

@Kovensky Unfortunately the stack trace is not helpful without the JS input and uglify options. Could you please file a new bug report and fill out the issue template?

[Jessidhia]

I'm not sure I'll be able to provide the input, or even useful input (the bundle that is crashing is enormous and all of it is work-related proprietary code...); but these are the uglifyOptions:

uglifyOptions: ({
  ecma: 5,
  compress: {
    unsafe_math: true,
    unsafe_proto: true,
    unsafe_regexp: true
  },
  warnings: false
})

I'll see if disabling the unsafe stuff helps and open a bug report if I learn anything; but it might be better for someone else to provide the details if possible.

[kzc]

There may be an infinite deep AST clone going on in https://github.com/mishoo/UglifyJS2/issues/2438#issuecomment-342058935 but without the input source involved we don't know how it comes about.

It's not difficult to make a reduced test case from large sources. Just disable minify in webpack to produce an uncompressed file. Run that file through the CLI with uglifyjs -b to remove the comments and beautify it. Then repeatedly comment out large sections of code and run the file through uglifyjs -c until you have a small test case exhibiting the error.

[kzc]

isolated the bug - see #2442