Validate Input Objects do not contain non-nullable circu…

[spawnia]

…lar references

The first two to tests are there to avoid false positives when checking for circular references.

Tests 3 and 4 are failing right now but show what should happen.

graphql/graphql-spec#445 contains the proposed additions to the spec.

[IvanGoncharov]

@spawnia Thanks for PR, your SDL examples look great 👍

However parse function doesn't do any validation beyound checking that correctness of GraphQL grammar.
This check should be performed by validateSchema function:

graphql-js/src/type/validate.js

Lines 48 to 57 in 4aca994

	/**
	* Implements the "Type Validation" sub-sections of the specification's
	* "Type System" section.
	*
	* Validation runs synchronously, returning an array of encountered errors, or
	* an empty array if no errors were encountered and the Schema is valid.
	*/
	export function validateSchema(
	schema: GraphQLSchema,
	): $ReadOnlyArray<GraphQLError> {

Can you please move your tests here:
https://github.com/graphql/graphql-js/blob/master/src/type/__tests__/validation-test.js#L1397

[IvanGoncharov]

@spawnia Preferably test cases should match examples from graphql/graphql-spec#445

[spawnia]

Unfortunately, implementation of this is not trivial and i think i will not be able to do it soon, i might implement it in PHP since i know that better.

It would be cool if maybe someone who has more experience with the project can take a shot of doing the actual validation?

[IvanGoncharov]

@spawnia Don't want this proposal to stuck so I created a draft implementation in #1359. I don't think it's ready to be merged but hopefully, it allows us to continue the conversation in graphql/graphql-spec#445

[IvanGoncharov]

@spawnia Since #1359 superseded this PR can I close it?

[spawnia]

Yep, thank you a lot for implementing this! Closed in favour of #1359