vm.Module.evaluate() morphs loader errors into module evaluation rejections

[joyeecheung]

This came up in #60205 (comment) when I was trying to make vm.Module.evaluate() return the module evaluation promise as-is (so synchronously fulfilled for synthetic modules and source text modules without TLA). Currently the validation errors, ERR_VM_MODULE_STATUS, THROW_ERR_SCRIPT_EXECUTION_TIMEOUT, and THROW_ERR_SCRIPT_EXECUTION_INTERRUPTED would always be rejected, so for a synchronous loader, they would either have to expose these underlying rejections to users when the loading goes wrong, or be forced to become asynchronous as it cannot catch these errors synchronously and paint it over. i.e. they cannot do something like this:

function syncLoad() {
  try {
    mod.evaluate();
  } catch(e) {  // This allows the user to get the loader errors synchronously
    if (e.code === 'ERR_VM_MODULE_STATUS' ||
        e.code === 'ERR_SCRIPT_EXECUTION_INTERRUPTED' ||
        e.code === 'ERR_SCRIPT_EXECUTION_TIMEOUT') {
      // fix it up and try again, or error and explain to user what to do
      // but hide the errors that do not directly come from module code
      // as implementation detail
    }
  }
  if (mod.status === 'errored') {
    throw mod.error;  // It's an evaluation error from the module code
  }
  return mod.namespace;
}

Opening a separate issue to discuss if there's another way to make this possible other than just making it throw these loader errors synchronously.

[legendecas]

Given that an instance of vm.Module (either vm.SourceTextModule or vm.SyntheticModule) can only be evaluated once, the result of the evaluation can be put on the instance, similar to vm.Module.error:

class Module {
  evaluate(): void;
  evaluated: Promise;  // Maps to CyclicModuleRecord.[[TopLevelCapability]]

  get error(): Error | undefined; // Existing property to get CyclicModuleRecord.[[EvaluationError]]
  hasAsyncGraph: bool; // Indicates if evaluate() can res
}

This makes the evaluate method always synchronous, not returning a promise indicating it is async. Still, for SourceTextModules that contain TLA, the async result can be obtained from await module.evaluated. And invoking module.evaluate() multiple times will not result in evaluation again.

However, this would be breaking if it starts throwing errors synchronously.