Improve error reporting/debugging of provide/inject, or allow require flag for inject

[johnhargrove]

What problem does this feature solve?

Currently when an inject fails to resolve, nothing happens, and the injected value just remains untouched. This seems like an opportunity to warn the developer that an inject could not be resolved.

Perhaps this is intended behavior. Maybe it makes sense that sometimes an injection would not be resolved. If that is the case, could there be a way to indicate a given inject is required? A stricter injection method?

My current workaround is to throw an error if the object is undefined as of create (since injects are resolved by then), but it's a manual step that must be made in many places.

What does the proposed API look like?

If a new API is needed to support this, I am not sure how to design it.

As for warning, I was hoping that when an inject could not be resolved, there would be a warning in the browser console.

[maciej-ka]

@johnhargrove could you give an example of failing inject? I'm not sure when can this happen.

[johnhargrove]

@Lokson This is any situation in which a child component has an inject which can't be satisfied by a provide in itself or any of its component ancestors, including the root Vue object itself.

I ran into this while developing a validation service. Basically, I have a ValidationService class which is a provide on a top level component which represents a collection of form inputs. The inputs themselves are very complicated, so they are their own Vue components:

 FormComponent (provides ValidationService)
 |-- ComplicatedInput (expects ValidationService inject)
 |-- ComplicatedInput (expects ValidationService inject)

If, when building this, I forget to provide the ValidationService on the parent FormComponent, the ComplicatedInput components will silently never have their reference to ValidationService injected. This results in errors related to accessing members of an undefined object, etc.

My theory here and the reason for this feature request is that getting some kind of indication that an inject went unsatisfied seems useful for development.

[Anamasi30]

[email protected]