Errors subclasses instances are replaced by base Error

[ntrrgc]

Issue description or question

I run a series of test I wrote a long time ago and suddenly two of them were failing... After running several experiments I found Wallaby is changing the semantics of this:

class MyError extends Error {
    myMethod() {
        return "meow";
    }
}

console.log(new MyError() instanceof MyError);
console.log(new MyError().myMethod);

Running the previous code in a browser returns this, as expected:

true
function myMethod() {
        return "meow";
    }

But running it in Wallaby returns something not expected at all:

false
undefined

Wallaby.js configuration file

module.exports = (w) => {
    return {
        files: [
            "src/**/*.ts"
        ],
        tests: [
            "spec/**.spec.ts"
        ],
        compilers: {
            "**/*.ts": w.compilers.typeScript({module: "commonjs"}),
        },
        debug: true,
        env: {
            type: "node"
        },
        testFramework: "mocha",
        setup: function (wallaby) {
            require("bluebird").config({
                longStackTraces: true
            })
        }
    }
}

Code editor or IDE name and version

PHPStorm 2016.3

OS name and version

Arch Linux

[ArtemGovorov]

Interesting one.

This issue is not wallaby.js specific, but TypeScript compiler version specific (same happens with Babel BTW). You may try compiling the code with ./node_modules/.bin/tsc, running it in node and you'll get the same result.

Have a look into:
microsoft/TypeScript#12123
microsoft/TypeScript#12058
microsoft/TypeScript#12145
microsoft/TypeScript#12581
microsoft/TypeScript#10166
microsoft/TypeScript#12279