improve reporting resolver failures

[voideanvalue]

I was trying to introduce resolvers to relayjs/relay-examples (in the nextjs example, manually hacked around the haste style requires printed by the compiler). I couldn't figure out why things weren't working for the longest time. The resolver module factory was getting executed but the resolver function didn't. Noting down some thoughts here for future me.

• __log provided to environment didn't show anything. I later realized requiredFieldLogger reports it but I totally didn't consider using it before I understood why the resolver wasn't getting invoked (in fact, that's when I remembered us talking about reporting resolver errors via requiredFieldLogger in the past). requiredFieldLogger probably needs a rename. maybe worth thinking about reporting/logging interface more broadly too.

• I eventually figured out that the issue was caused by export default function MyResolver... and resolverModule: require('...') not playing well together. We don't attempt to unwrap default anywhere in RelayReader. We do in loadEntryPoint and GraphQLTag... probably worth having a utility function somewhere to share across all three and any future places we load modules.

[captbaritone]

I have a TODO somewhere to rename requiredFieldLogger. It's on my list. We also need to update the types (Flow and Typescript) to make that logger non-optional.

CC @tbezman: Heads up about the module resolution issue with Resolvers and default exports.

[sibelius]

we got this error

Relay Environment Configuration Error (dev only): `@required(action: LOG)` requires that the Relay Environment be configured with a `requiredFieldLogger`.
    at RelayModernEnvironment.defaultRequiredFieldLogger [as requiredFieldLogger]

is this related ?

[voideanvalue]

@sibelius I think that's different... it's saying that @required(action: LOG) is being used but the RelayEnvironment instance you're using doesn't have requiredFieldLogger configured