GAP-0002 Add Field Extensions Spec

[egoodwinx]

Copied from graphql/graphql-spec#1196 and graphql/graphql-spec#1162

[magicmark]

# This is not valid GraphQL

So is the idea to compile this out of the SDL before passing to a GraphQL server?

[egoodwinx]

So is the idea to compile this out of the SDL before passing to a GraphQL server?

Yes

[magicmark]

I think this would benefit then from being layered on top of the soon-to-be-proposed language in the spec to clarify the difference between "human written"(?) schemas and "runtime" schemas. Not required for this to merge, but worth following along!

@benjie wdyt about a dedicated 2xxx range for "language and syntax extensions"?

side note, not directly relevant to this proposal but:

• since this is valid syntax folks don't need to worry about existing tooling (syntax highlighters, ast parsing functions and such) breaking on schema that uses this - I think it's only invalid at runtime when validation rules get applied.
• I wonder what should happen if a GAP proposes new syntax - and at that point you're on your own, there's no guarantee that any other tooling would work. Obviously this isn't a problem to worry about for now, and could be solvable in future I imagine with plugins (similar to babel) and whatnot.