Some AST consistency questions

[stubailo]

I'm currently working on some AST stuff, and I'm running into a few situations where there is different behavior in a way that doesn't seem intentional. Two examples so far:

Operation name

parse(`query { x }`);

returns "name": undefined in the operation definition.

parse(`{ x }`);

returns "name": null in the operation definition.

Variable definitions

parse(`query { x }`);

returns "variableDefinitions": [] in the operation definition.

parse(`{ x }`);

returns "variableDefinitions": null in the operation definition.

Conclusion

Looks like these two in particular are because of this line and similar ones that hardcode the default values:

graphql-js/src/language/parser.js

Line 275 in b17d5f5

name: null,

@leebyron - Would you be interested in a PR to make these different situations consistent, for example to always return null for the operation name and [] for variable definitions?

I'd be happy to submit a PR with all of the situations I find, but first wanted to check if that would be desirable - I can imagine some tools might depend on this output not changing.