struct type in the argument throws an error about babel-plugin-tcomb

[volkanunsal]

The error comes from this function here:

// tcomb/index.js:125:13
function assert(guard, message) {
  if (guard !== true) {
    if (isFunction(message)) { // handle lazy messages
      message = message();
    }
    else if (isNil(message)) { // use a default message
      message = 'Assert failed (turn on "Pause on exceptions" in your Source panel)';
    }
    exports.fail(message);
  }
}

But not sure how it decides the guard has failed.

[gcanti]

When the assert fails, does args contain an instance of pipe_args_t?

A function like this:

function f(args: pipe_args_t) => {
  ...
}

will be transformed by the plugin to:

function f(args: pipe_args_t) => {
  t.assert(pipe_args_t.is(args)); // <= args here must be an instance of pipe_args_t
  ...
}

[volkanunsal]

Yup, there is an instance of pipe_args_t in there. The problem is this returns false:

pipe_args_t.is({query: {a: 1})

Do I need to ensure the args is wrapped in a struct?

[gcanti]

pipe_args_t.is({query: {a: 1}); // false, {query: {a: 1} is not an instanceof pipe_args_t
pipe_args_t.is(new pipe_args_t({query: {a: 1})); // true

[gcanti]

I mean: in tcomb, if S is a struct S.is(x) returns true if and only if x instanceof S is true

[volkanunsal]

Gotcha. It would be sweet if the plugin automatically wrapped the objects in a struct somehow, so I wouldn't have to worry about doing this everywhere, but I would understand if this is not in the scope.

[gcanti]

That would couple your code with babel-plugin-tcomb: in the production build you may want to remove the plugin (and its overhead) from the workflow.

import t from 'tcomb'

const Person = t.struct({
  name: t.String,
  surname: t.String
})

Person.prototype.getFullName = function getFullName() {
  return `${this.name} ${this.surname}`
}

function greetings(person: Person) {
  return `Hello ${person.getFullName()}`
}

greetings({name: 'Giulio', surname: 'Canti'}) // <= this would work in development, but throws in production!!!