Warn when calling refetch({ variables }) instead of refetch(variables)

[benjamn]

The refetch method of ObservableQuery takes a single optional positional argument, specifying (additional) variables to include when refetching the query.

A common pitfall is passing an object containing a variables property to refetch (you may be thinking of setOptions?), which is almost always a mistake, unless the query declares a variable named $variables (uncommon).

This PR displays a helpful warning in these cases (with tests to prove it). For example:

Called refetch({"variables":["d","e"]}) for query QueryWithoutVariables, which does not declare a $variables variable.
Did you mean to call refetch(variables) instead of refetch({ variables })?

Related:

• Clarify refetch and useLazyQuery #8692

[hwillson]

Woohoo I love this - thanks @benjamn!

[stemmlerjs]

Wow, thanks for the quick turnaround on this @benjamn! The console message looks great. I think this should help for sure.