Coercing Field Arguments

Fields may include arguments which are provided to the underlying runtime in order to correctly produce a value. These arguments are defined by the field in the type system to have a specific input type: Scalars, Enum, Input Object, or List or Non‐Null wrapped variations of these three.

At each argument position in a query may be a literal value or a variable to be provided at runtime.

CoerceArgumentValues

(

objectType

,

field

,

variableValues

)

1. Let coercedValues be an empty unordered Map.
2. Let argumentValues be the argument values provided in field .
3. Let fieldName be the name of field .
4. Let argumentDefinitions be the arguments defined by objectType for the field named fieldName .
5. For each argumentDefinition in argumentDefinitions :
   1. Let argumentName be the name of argumentDefinition .
   2. Let argumentType be the expected type of argumentDefinition .
   3. Let defaultValue be the default value for argumentDefinition .
   4. Let value be the value provided in argumentValues for the name argumentName .
   5. If value is a Variable:
      1. Let variableName be the name of Variable value .
      2. Let variableValue be the value provided in variableValues for the name variableName .
      3. If variableValue exists (including null ):
         1. Add an entry to coercedValues named argName with the value variableValue .
      4. Otherwise, if defaultValue exists (including null ):
         1. Add an entry to coercedValues named argName with the value defaultValue .
      5. Otherwise, if argumentType is a Non‐Nullable type, throw a field error.
      6. Otherwise, continue to the next argument definition.
   6. Otherwise, if value does not exist (was not provided in argumentValues :
      1. If defaultValue exists (including null ):
         1. Add an entry to coercedValues named argName with the value defaultValue .
      2. Otherwise, if argumentType is a Non‐Nullable type, throw a field error.
      3. Otherwise, continue to the next argument definition.
   7. Otherwise, if value cannot be coerced according to the input coercion rules of argType , throw a field error.
   8. Let coercedValue be the result of coercing value according to the input coercion rules of argType .
   9. Add an entry to coercedValues named argName with the value coercedValue .
6. Return coercedValues .

Variable values are not coerced because they are expected to be coerced before executing the operation in

CoerceVariableValues

()

, and valid queries must only allow usage of variables of appropriate types.