Add multiple errors - with correct nesting to a query

[axos88]

Related to #629:

Thanks for giving that tip on ctx.add_error in the referenced issue. I'm wondering if it's possible to add an error for a subfield/argument?

For example in case of multiple validation errors, in the field's resolve function I would like to add an error that that the argument item_no was out of bounds, and the argument commission cannot be set if the commission_type is not set.

ctx.add_error would return the query in the fields field of the error, whereas it would be much more self-explanatory (and easier for the frontend), if it were the erroneous argument, so it would not need a complex decision logic to show it to the user.

I'm thinking something like ctx.get_context_for(:item_no).add_error(...)

[axos88]

Ok, I found a way, although it is a bit cumbersome:

e = GraphQL::ExecutionError.new('message')
e.path = ctx.path + ["item_no"]
ctx.add_error(e)

[rmosolgo]

Glad you found a solution! I think a new mutation API could provide better support for this, I'll keep it in mind at #1275