TypeError: Cannot read property 'hasChild' of undefined

[urbnjamesmi1]

Version

3.5.1

Reproduction link

https://jsfiddle.net/xkLh4njp/

Steps to reproduce

1. Create a Vuex store.
2. Call store.hasModule() with an array of at least 2 elements where neither module has been registered to the store.

What is expected?

store.hasModule() to return false

What is actually happening?

Error "TypeError: Cannot read property 'hasChild' of undefined" is thrown

[cuebit]

Thanks for opening this issue and creating a PR. However, this is expected behaviour at this time.

In the same manner as registerModule behaves, where a parent module must be registered before any descendants, the hasModule should verify the parent before verifying any descendants.

Negating the return type, when checking for a descendant where a parent module may not exist, implies the parent may exist when really you want this behaviour to be explicit.

[urbnjamesmi1]

Can the documentation for hasModule and registerModule at least be updated with this explanation? Or maybe a custom error can be thrown explaining that a specific parent module doesn't exist.

[cuebit]

For sure, this is an opportunity to offer clarity in the docs. I don't think throwing errors are a useful way to identify this concern, since the hasChild method naming is self explanatory in the error thrown when a child module cannot be reached.