extern functions behave differently in Wing simulator

[Chriscbr]

I tried this:

I made a Wing project with these two files, and ran wing test:

// main.w
class Util {
  extern "./superjson.js" static inflight dostuff();
}

test "superjson" {
  Util.dostuff();
}

// superjson.js
const superjson = require("superjson");

exports.dostuff = function() {
    const string = superjson.stringify(
        { handle: 'sim-3', method: 'dec', args: [ undefined, 'my-key' ] }
    );
    console.log(string);
}

This happened:

This is printed by the test:

{"json":{"handle":"sim-3","method":"dec","args":[null,"my-key"]},"meta":{"referentialEqualities":{}}}

I expected this:

I expected the output to match the output when I run superjson in a Node REPL:

Welcome to Node.js v18.14.1.
Type ".help" for more information.
> require("superjson").stringify({ handle: 'sim-3', method: 'dec', args: [ undefined, 'my-key' ] })
'{"json":{"handle":"sim-3","method":"dec","args":[null,"my-key"]},"meta":{"values":{"args.0":["undefined"]}}}'

Notice that the "meta" value contains an annotation saying that args.0 needs to be parsed as "undefined" instead of null. This annotation is not added when running in Wing simulator.

Is there a workaround?

No response

Component

SDK

Wing Version

0.29.11

Node.js Version

18.14.1

Platform(s)

MacOS

Anything else?

No response

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[Chriscbr]

Another example of an extern function that runs fine in Node.js, but throws an error in Wing:

exports.dostuff = function() {
    const assert = require("assert");
    const string = "{\"key1\":1,\"key2\":2}";
    const obj = ({"key1": 1,"key2": 2});
    assert.deepStrictEqual(JSON.parse(string), obj);
}

Due to this bug, we see different equality behavior between preflight and inflight:

let s = "{\"key1\":1,\"key2\":2}";
let obj = Json { "key1": 1, "key2": 2 };

assert(Json.parse(s) == obj); // OK

test "deepCopy()" {
  let s = "{\"key1\":1,\"key2\":2}";
  let obj = Json { "key1": 1, "key2": 2 };

  assert(Json.parse(s) == obj); // error
}

[Chriscbr]

Maybe adding assert to the VM context will fix this?

wing/libs/wingcompiler/src/compile.ts

Line 245 in a572271

const context = vm.createContext({

[staycoolcall911]

Changed priority p3 -> p1

[Chriscbr]

In the Json equality example above, Wing is swallowing the error message (it just reports assertion failed: Json.parse(s) == obj). This Node.js code reproduces the full error:

let code = `
const j = { key1: 1, key2: 2 };
const k = "{\\"key1\\":1,\\"key2\\":2}";
require('assert').deepStrictEqual(j, JSON.parse(k));
console.log("done");
`
eval(code);

let vm = require("vm").runInNewContext(code, {
    require,
    console,
    JSON,
});
console.log(vm);

When eval() is called on code, it works, but when code is executed by the vm it throws an error like this:

node:assert:124
  throw new AssertionError(obj);
  ^

AssertionError [ERR_ASSERTION]: Values have same structure but are not reference-equal:

{
  key1: 1,
  key2: 2
}

    at evalmachine.<anonymous>:4:19
    at Script.runInContext (node:vm:141:12)
    at Script.runInNewContext (node:vm:146:17)
    at Object.runInNewContext (node:vm:300:38)
    at Object.<anonymous> (/Users/chrisr/dev/wing-test/vm.js:9:24)
    at Module._compile (node:internal/modules/cjs/loader:1254:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1308:10)
    at Module.load (node:internal/modules/cjs/loader:1117:32)
    at Module._load (node:internal/modules/cjs/loader:958:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: { key1: 1, key2: 2 },
  expected: { key1: 1, key2: 2 },
  operator: 'deepStrictEqual'
}

[Chriscbr]

Related to #4118

[github-actions]

Hi,

This issue hasn't seen activity in 60 days. Therefore, we are marking this issue as stale for now. It will be closed after 7 days.
Feel free to re-open this issue when there's an update or relevant information to be added.
Thanks!

[garysassano]

Keep.

[monadabot]

Congrats! 🚀 This was released in Wing 0.59.43.