ConvertEmptyStringsToNullDirective not executed when applied on fields where the argument is an input type

[dennis-koster]

Describe the bug
The ConvertEmptyStringsToNullDirective is not executed when it is applied globally or to an input, where the expected behaviour would be that it would apply the conversion recursively. It appears to me that this change has introduced this bug, because the added if check now makes it so that the sanitize method is only applied if the type of input is a string, negating the intended recursive nature.

Expected behavior/Solution
The directive should be executed when applied to an input or globally, as described in the documentation.

Steps to reproduce

Given the following schema:

extend type Mutation @guard {
    updateMe(input: UpdateMeInput): User!
        @field(resolver: "App\\GraphQL\\Mutations\\UpdateMe")
}

input UpdateMeInput {
    firstName: String @rules(apply: ["filled"])
    insertion: String @rules(apply: ["nullable"])
    lastName: String @rules(apply: ["filled"])
}

Execute the following mutation:

updateMe(input: {
    insertion: "",
}) {
    insertion
}

Expected outcome would be for the insertion attribute to be converted to null in the following scenarios:
1.\Nuwave\Lighthouse\Schema\Directives\ConvertEmptyStringsToNullDirective::class, is added to the field_middleware array in the lighthouse.php configuration file.
2. The directive is applied to the input as such:

extend type Mutation {
    updateMe(input: UpdateMeInput): User! @convertEmptyStringsToNull
        @field(resolver: "App\\GraphQL\\Mutations\\UpdateMe")
}

Lighthouse Version
v6.43.1

[spawnia]

Can you add provide a pull request with a failing test case?

[dennis-koster]

@spawnia Let me know if this is sufficient for you to reproduce the error: #2611.

It seems like situations where the @field directive is used are not covered.

[spawnia]

The issue in your tests was that @convertEmptyStringsToNull does not apply to non-nullable inputs when used on fields, see 5ee83d5. I improved the docs for this in 45e1cbb.

Please let me know if there is another issue, and please consider sponsoring.

[spawnia]

Thank you for your persistence @dennis-koster, fixed with https://github.com/nuwave/lighthouse/releases/tag/v6.44.2.