ensureNextIsCalled Function

Ensure that the given function will always "yield" by calling next on its behalf if needed.

next will be called implicitly in the following cases:

• the given function is undefined
• the given function only accepts the ctx parameter

This is necessary when you're wrapping an exit hook since you want to invoke the original exit hook before you do your thing, and in that case you want to ensure that that hook will actually call you!

Examples:

// No function:
ensureNextIsCalled(undefined)(ctx, function next() {
  console.assert(true);
})

// Yes function but it's not aware of `next`:
ensureNextIsCalled(function() {})(ctx, function next() {
  console.assert(true);
})

// Yes function but it's not aware of `next` either:
ensureNextIsCalled(function(ctx) {})(ctx, function next() {
  console.assert(true);
})

// Yes function and it's aware of `next`, we'll do nothing:
ensureNextIsCalled(function(ctx, next) { next() })(ctx, function next() {
  console.assert(true);
})