vm.runInContext: eval a strict function

[DmitrySoshnikov]

Evaluated strict functions, when ran inside vm.ranInContext do not capture environment.

This works (file test.js):

var code = `
var foo = {m: 1};

function bar() {
  "use strict";
  return foo;
}
`;

eval(code);

bar();

Node session:

> vm.runInNewContext(fs.readFileSync('/Users/dmitrys/test.js', 'utf-8'))
{ m: 1 }
>

This doesn't:

function main() {

  var code = `
    var foo = {m: 1};

    function bar() {
      "use strict";
      return foo;
    }
  `;

  eval(code);

  bar(); // foo is not defined

}

main();

Node session:

> vm.runInNewContext(fs.readFileSync('/Users/dmitrys/test.js', 'utf-8'))
undefined:6
      return foo;
             ^
ReferenceError: foo is not defined
    at bar (eval at main (evalmachine.<anonymous>:13:8), <anonymous>:6:14)
    at main (evalmachine.<anonymous>:15:3)
    at evalmachine.<anonymous>:19:1
    at ContextifyScript.Script.runInNewContext (vm.js:18:15)
    at Object.exports.runInNewContext (vm.js:49:17)
    at repl:1:4
    at REPLServer.defaultEval (repl.js:154:27)
    at bound (domain.js:254:14)
    at REPLServer.runBound [as eval] (domain.js:267:12)
    at REPLServer.<anonymous> (repl.js:308:12)

Also the code works if there is no "use strict" for foo.

[domenic]

Possibly related: #548

This is almost certainly a V8 bug. @trevnorris tracked down #548 to V8s after 3.28.22 failing. I'll go see if there's any obvious culprit...

[amasad]

could be related to: nodejs/node-v0.x-archive#8721?

[DmitrySoshnikov]

How likely this can be fixed in soon time? Is there any ETA? We're blocked by this issue at the moment, and will have to restructure our tests to not to use eval(...) (we use it to evaluate a translated to JS code, and run it). Seems we don't have any alternative to eval in this case (since Function doesn't capture environment either).

[trevnorris]

@domenic this related to the fact we wrap all our scripts to prevent global variable pollution?

[DmitrySoshnikov]

@trevnorris, seems strict functions just don't capture the local scope at all (and see only global environment, similarly to the Function(...) functions). Notice that the first example works, since bar is global, and sees the global foo in first case. But once it's wrapped into the main function, the bar doesn't see foo anymore.

[targos]

I does not seem to be confined to the vm module. I get the same error if I directly run node test.js

Edit: and with node --use-strict test.js it changes to ReferenceError: bar is not defined

[DmitrySoshnikov]

@targos, the --use-strict adds a Program-level strict mode? Then the bar function correctly won't be created in the caller's environment (in the environment of main).

However, we run the non-strict mode, and only the function bar itself is strict. The strictness of a function should not affect (per ES5) the environment which should be captured regardless.

So I'd say it's still the issue of the vm module.

[DmitrySoshnikov]

OK, seems it's really Node/V8 generic evaluation issue, not limited to the vm module. Updated example and the outputs in the Node 0.8 (works), and Node 0.10 (doesn't work):

The ~/test.js:

function main() {

  var code = [
    "var foo = {m: 1};",
    "",
    "function bar() {",
    "  'use strict';",
    "  console.log(foo);", // foo isn't captured in 0.10
    "}",
  ].join('\n');

  eval(code);

  bar(); // foo is not defined, since node 0.10, works in 0.8

}

main();

Tests:

dmitrys-mbp:~ dmitrys$ nvm use 0.8
Now using node v0.8.28 (npm v1.2.30)
dmitrys-mbp:~ dmitrys$ node ~/test.js
{ m: 1 }
dmitrys-mbp:~ dmitrys$ nvm use 0.10
Now using node v0.10.38 (npm v1.4.28)
dmitrys-mbp:~ dmitrys$ node ~/test.js

undefined:5
  console.log(foo);
              ^
ReferenceError: foo is not defined
    at bar (eval at main (/Users/dmitrys/test.js:12:8), <anonymous>:5:15)
    at main (/Users/dmitrys/test.js:14:3)
    at Object.<anonymous> (/Users/dmitrys/test.js:18:1)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:935:3
dmitrys-mbp:~ dmitrys$

[domenic]

Yeah, if this is related to nodejs/node-v0.x-archive#8721, it is more a Node issue than a V8 issue, as we were unable to reproduce the problem in D8 :-/. (I still believe the problem stems from a V8 bug though, given that it regressed in a V8 upgrade.)

[DmitrySoshnikov]

Yeah, seems it's the same issue. Would still be great to get some ETA of fixing it.