NullReference exception in ReqlExpr

[oliverjanik]

You've got an override for == operator here:

    public static ReqlExpr operator ==(ReqlExpr a, ReqlExpr b)
    {
      return (ReqlExpr) a.eq((object) b);
    }

This throws when I do a comparison like this:

if (expr == null) ...

Got me very confused for a second. Can null be special cased here?

[bchavez]

Hey @oliverjanik , I think you need to use ReferenceEquals when comparing null with the AST ReqlExpr.

Could you provide more context with how you're using and why you're checking null?

Thanks,
Brian

[oliverjanik]

Yeah that's what I ended up doing, but it confused the hell out of me for a while. Is it intended to be like that?

[bchavez]

@oliverjanik Yea, the operator overload for == is intended. This allows us to write queries like:

.Filter(g => g[nameof(Game.points)].Eq(9))
.Filter(g => g[nameof(Game.points)] == 9) //op overload

Fancy! 👍

Wiki docs for this are here: https://github.com/bchavez/RethinkDb.Driver/wiki/Extra-C%23-Driver-Features#implicit-conversion-operator-overload

[oliverjanik]

g[nameof(Game.points)] is never null in these situations, would a null check break anything?

[bchavez]

Hey Oliver,

g[nameof(Game.points)] isn't null per se but I think the field in the JSON document could be null. The server would have the necessary information.

Consider what happens with:

(g => g[nameof(Game.points)] == 9)

This check doesn't happen on the client, it happens on the server. == 9 gets converted into ReQL: .Eq(9). Same would apply for null: == null -> .Eq(null).

🍷 🌴 _"Get drunk on the good life, I'll take you to paradise..."_

[oliverjanik]

Alright then, I'm closing this issue.

On a sidenote: It feels like Rethink guys reinvented Expression trees in their Java driver.