Question regarding unmarshalReflect

[alexkohler]

Hi there, I'm currently running into an issue that I think may potentially be a bug, but wanted to get some background on the guarantees of unmarshalReflect (and the general premise of how this library performs unmarshaling). Inside of of the unmarshalReflect's reflect.Array case, we have the following:

	case reflect.Array:
		arr := reflect.New(rv.Type()).Elem()
		elemtype := arr.Type().Elem()
		switch {
		case av.B != nil:
			for i, b := range av.B {
				arr.Index(i).Set(reflect.ValueOf(b))
			}
			rv.Set(arr)
			return nil

How are you guaranteeing that len(av.B) is equal to (or less than) arr.Len()?

[guregu]

Hello
Looks like a bug to me 😅
After messing around with encoding/json a bit, it seems to discard values that won’t fit into the array
We should probably match that behavior
Although I think an error message might be more useful 🤔

[alexkohler]

Either approach seems better than a panic 😄 It might be more idiomatic to match encoding/json's behavior, but the behavior should be explicitly documented either way.

[guregu]

I released v1.7.1 which fixes this. I decided to return an error when the array is too small. I imagine most of the time unmarshaling into a too-small array is a mistake instead of intended behavior, and silently truncating data is scary. I can always change this later if there's demand for it.

I haven't updated the docs yet but I'd like to have more explicit info about how each type is handled, I added this to #45.

Thanks for the bug report!

[guregu]

Whoops, forgot to include the fix for lists -> arrays in v1.7.1.
Released v1.7.2 which takes care of that.