Clarify 'Values of Correct Type' rule relates to literals #1118
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@graphql/tsc I would love to get your input on this change. |
| - Let {type} be the type expected in the position {value} is found. | ||
| - {value} must be coercible to {type}. | ||
| - {value} must be coercible to {type} (with the assumption that any | ||
| {variableUsage} nested within {value} will represent a runtime value of the |
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There are two conditions mentioned below, that the variable usage is allowed and that the variable value will coerce at runtime, but only one assumption is mentioned here. Is that intentional?
| {variableUsage} nested within {value} will represent a runtime value of the | |
| {variableUsage} nested within {value} is allowed and will represent a runtime value of the |
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It is deliberate: coercion happens at runtime where variables are already resolved; for us to run coercion during validation we need to run a slightly modified coercion - the modification being that it assumes (singular assumption) each variable reference it sees (something coercion would not normally understand) is equivalent to an arbitrary runtime value of that variable's type. It does not need to assume that the variable is allowed, from its point of view the variable exists whether it's allowed or not.
The foundation of that singular assumption is the behaviour of "All Variable Usages Are Allowed" combined with "Coercing Variable Values" - these aren't assumptions, these are specified behaviours.
An Input Value is defined as being either a variable (if not const) or one of the literal types (IntValue, FloatValue, StringValue, BooleanValue, NullValue, EnumValue, ListValue or ObjectValue).
The rule "Values of Correct Type" states:
However, an input value can be a variable, and variable coercion is handled at runtime (by CoerceVariableValues). Further, we already have a rule that validates that variables are only used in the positions in which they are allowed: All Variable Usages Are Allowed.
It seems to me that "Values of Correct Type" only meant to handle literal input values, so I've added the word "literal" for clarity. I've also expanded the explanation to reference where to look for variable input value validation. Since input coercion for Input Object references "runtime value", and validation doesn't have access to runtime values, I've made explicit the assumption that values represented by variables will be of the variable's type.
This is an alternative solution to, and
Thank you to @yaacovCR for pointing out this deficiency 🙌