createInjectionToken wrongfully disregards falsy argument passed to generated provider function

[diegovilar]

Suppose for whatever reason you want to provide a value like this:

const [injectSomeValue, provideSomeValue] = createInjectionToken(factory);

function factory(): number {
  return 1;
}

Later on you actually provide a value so it can be injected instead of the factory generated one:

providers: [provideSomeValue(0)]

Because of how the provider function (provideSomeValue) created by createProvideFn decides whether to use the configured factory or the value that was provided to provideSomeValue, any provided value that evaluates to falsy (0, "", false, null, undefined, etc) will be disregarded and the factory will be used instead.

Instead of evaluating the optionally passed argument itself, maybe evaluate if an argument was actually passed instead?