Schema Coordinates

[leebyron]

Depends on #3115

Implements graphql/graphql-spec#794

Adds:

• DOT punctuator in lexer
• Improvements to lexer errors around misuse of .
• Minor improvement to parser core which simplified this addition
• SchemaCoordinate node and isSchemaCoodinate() predicate
• Support in print() and visit()
• Added function parseSchemaCoordinate() since it is a parser entry point.
• Added function resolveSchemaCoordinate() and resolveASTSchemeCoordinate() which implement the semantics (name mirrored from buildASTSchema) as well as the return type GraphQLSchemaElement

[magicmark]

Amazing!

This is way beyond what I was hacking with. Hadn't even considered reusing the existing parser. (I was fiddling around with regexes...)

Thanks for putting this together - this makes a lot of sense.

[magicmark]

:)

[leebyron]

Great feedback - I think I've resolved both:

• Replaced fieldName with memberName in the AST to ensure it's generalized between fields, input fields, and enum values. Those are all specific instances of the general pattern of "members of a set", which is pretty common terminology for this generalized dot access pattern.
• Took both of your great suggestions for wrapping the return type of resolveSchemaCoordinate - the ResolvedSchemaElement type is now a union of wrappers. This had the added benefits of disambiguating between "field argument" and "directive argument" and including the coordinate context in the return value