Validation of variable values

I’m curious why it’s not possible to validate the values of variables using the validate framework.

For example, suppose I have a very simple validator that wants to assert the value for argument name contains only ascii characters, given this schema:

type Query {
    hello(name: String!): String!
}

I can implement this validator and it will work when the incoming request is this:

{
    'query': '{ hello(name: "foo") }'
}

but when the request is the following, I have no way of seeing the value for the VariableNode $myName from inside the validator:

{
    'query': 'query myQuery($myName: String!) { hello(name: $myName) }',
    'variables': {'myName': 'foo'}
}

It looks like it comes down to this bit of the code: https://github.com/graphql/graphql-js/blob/main/src/graphql.ts#L118-L122

Is there any reason why variableValues cannot also be passed in and made available to the validate framework?

[glasser]

My understanding is that the whole concept behind “validation” is that it is specifically a function of “operation + schema”. So for example, you can cache the result of parsing and validation and not run it multiple times for the same operation and schema if only variables are changing. (Apollo Server does this!)

That said, I would love to be able to separate the getVariableValues stage out of execute so that we can report them with different kinds of error codes (and plugin callbacks!) in our request processing pipeline. @IvanGoncharov do you think that sort of change would be a reasonable PR? Would love to brainstorm exactly how to structure it. (We’d similarly want to pull out the “make sure an operation name is provided if needed and that it matches an operation in the document if provided” step.)

[yaacovCR]

Update: #3302 supersedes #3193.