== raises an exception when Json.Encode.Values are not equal below the first level

[BrianHicks]

As in #1057, I expect this also happens on Json.Decode.Values—I can demonstrate it in my production code but Json.Encode.Value was simpler to make into an SSCCE.

Code on Ellie (reproduced below):

module Main exposing (main)

import Html exposing (text)
import Json.Encode exposing (Value, null, object)


value1 : Value
value1 =
    object [ ( "field", null ) ]


wrap : Value -> Value
wrap wrapped =
    object [ ( "wrapper", wrapped ) ]


main =
    Html.text (Debug.toString (wrap value1 == value1))

I expected this to print "False" but it crashed instead.

It appears that _Utils_eqHelp checks if either value is null but not if they are undefined. Then it tries to access a value like undefined[field], which raises an exception.

[avh4]

I expect this also happens on Json.Decode.Values

FYI, Json.Decode.Value is simply a type alias to Json.Encode.Value

[BrianHicks]

Yep, I know! That's why I expect it will happen on either, but I just wanted to be up front about which I tested with 😄

[evancz]

Equality is not supported for Json.Encode.Values for a variety of reasons. I talk about that a bit in #1057. It can also crash if the value contains a function. The long term fix is that "trying to use equality on JS values should be a type error".