@stream initialCount validation

[robrichard]

Context

From @benjie graphql/graphql-spec#742 (review)

There doesn't seem to be any validation rule enforcing that initialCount (if present) is greater than or equal to 0. I suggest adding this validation.

Decision

There was agreement in the Dec 2021 WG meeting to throw a field error when a negative initialCount is encountered during execution.

Status

• defined in spec
• implemented in graphql-js

[robrichard]

@benjie I think this validation would require variables to be known? Does that mean it must be done during execution and not during validation? Are there examples of anything else like this?

For example, this document is valid

query ($myInitialCount: Int) {
  listField @stream(initialCount: $myInitialCount)
}

But not if sent with the arguments {"myInitialCount": -1}

[benjie]

Yeah, we can’t do it at the validation stage. Maybe just add text stating that negative numbers are treated as zero. Or even that the behaviour of negative numbers is undefined (which allows for them to do something specific in future).

[maraisr]

If a value is in fact passed in, can it not fail validation of less than zero?

[benjie]

That would be inconsistent - passing a variable and an explicit argument with the same value (assuming typed correctly) should have the same effect.

[michaelstaib]

It still feels fishy I have to say. What about a runtime error if the value is incorrect?

[maraisr]

I think there's 2 types of validation, query validation and input/runtime valuation.

An "incorrect" input would still pass query validation, but a server could decide to fail input validation, but that is "consumer" side from the eyes of graphql.

[benjie]

Agree. This problem isn't really unique to @stream; e.g. Relay connections with first: -1 don't make sense. The difference being that the argument is to a directive versus a field. Quite a few GraphQL services have a second validation phase that runs "per-request" rather than "per-document" - this is required to do things like query cost limits, and is also useful for pagination limits, etc. The Guild in particular are keen to make this second phase more official. Relevant: graphql/graphql-js#3370 (comment)

[robrichard]

There was agreement in the Dec 2021 WG meeting to throw a field error when a negative initialCount is encountered during execution.

[maraisr]

Not related; super stoked to have you at the helm of these things @robrichard ❤️