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[RFC] Allow singular variables in list locations #509

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f4f53ed
Allow singular variables in list locations
taion Aug 29, 2018
16978d4
Remove CoerceVariableValues
taion Sep 1, 2018
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18 changes: 16 additions & 2 deletions spec/Section 5 -- Validation.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1857,7 +1857,10 @@ AreTypesCompatible(variableType, locationType):
* Let {nullableVariableType} be the nullable type of {variableType}.
* Return {AreTypesCompatible(nullableVariableType, locationType)}.
* Otherwise, if {locationType} is a list type:
* If {variableType} is NOT a list type, return {false}.
* If {variableType} is NOT a list type:
* Let {itemLocationType} be the unwrapped item type of {locationType}.
* Let {nullableItemLocationType} be the unwrapped nullable type of {itemLocationType} if {itemLocationType} is non-null, or {itemLocationType} if {itemLocationType} is nullable.
* Return {AreTypesCompatible(variableType, nullableItemLocationType)}.
* Let {itemLocationType} be the unwrapped item type of {locationType}.
* Let {itemVariableType} be the unwrapped item type of {variableType}.
* Return {AreTypesCompatible(itemVariableType, itemLocationType)}.
Expand All @@ -1884,7 +1887,7 @@ query intCannotGoIntoBoolean($intArg: Int) {

${intArg} typed as {Int} cannot be used as a argument to {booleanArg}, typed as {Boolean}.

List cardinality must also be the same. For example, lists cannot be passed into singular
List cardinality must be compatible. For example, lists cannot be passed into singular
values.

```graphql counter-example
Expand All @@ -1895,6 +1898,17 @@ query booleanListCannotGoIntoBoolean($booleanListArg: [Boolean]) {
}
```

However, for consistency with type coercion, singular values can be passed into lists,
including nullable singular values for nullable lists of non-nullable values.

```graphql example
query booleanCanGoIntoBooleanList($booleanArg: Boolean!) {
arguments {
booleanListArgField(booleanListArg: $booleanArg)
}
}
```

Nullability must also be respected. In general a nullable variable cannot
be passed to a non-null argument.

Expand Down
56 changes: 3 additions & 53 deletions spec/Section 6 -- Execution.md
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Expand Up @@ -28,13 +28,12 @@ request is determined by the result of executing this operation according to the
ExecuteRequest(schema, document, operationName, variableValues, initialValue):

* Let {operation} be the result of {GetOperation(document, operationName)}.
* Let {coercedVariableValues} be the result of {CoerceVariableValues(schema, operation, variableValues)}.
* If {operation} is a query operation:
* Return {ExecuteQuery(operation, schema, coercedVariableValues, initialValue)}.
* Return {ExecuteQuery(operation, schema, variableValues, initialValue)}.
* Otherwise if {operation} is a mutation operation:
* Return {ExecuteMutation(operation, schema, coercedVariableValues, initialValue)}.
* Return {ExecuteMutation(operation, schema, variableValues, initialValue)}.
* Otherwise if {operation} is a subscription operation:
* Return {Subscribe(operation, schema, coercedVariableValues, initialValue)}.
* Return {Subscribe(operation, schema, variableValues, initialValue)}.

GetOperation(document, operationName):

Expand Down Expand Up @@ -67,48 +66,6 @@ not later change, or a service may validate a request once and memoize the
result to avoid validating the same request again in the future.


### Coercing Variable Values

If the operation has defined any variables, then the values for
those variables need to be coerced using the input coercion rules
of variable's declared type. If a query error is encountered during
input coercion of variable values, then the operation fails without
execution.

CoerceVariableValues(schema, operation, variableValues):

* Let {coercedValues} be an empty unordered Map.
* Let {variableDefinitions} be the variables defined by {operation}.
* For each {variableDefinition} in {variableDefinitions}:
* Let {variableName} be the name of {variableDefinition}.
* Let {variableType} be the expected type of {variableDefinition}.
* Assert: {IsInputType(variableType)} must be {true}.
* Let {defaultValue} be the default value for {variableDefinition}.
* Let {hasValue} be {true} if {variableValues} provides a value for the
name {variableName}.
* Let {value} be the value provided in {variableValues} for the
name {variableName}.
* If {hasValue} is not {true} and {defaultValue} exists (including {null}):
* Add an entry to {coercedValues} named {variableName} with the
value {defaultValue}.
* Otherwise if {variableType} is a Non-Nullable type, and either {hasValue}
is not {true} or {value} is {null}, throw a query error.
* Otherwise if {hasValue} is true:
* If {value} is {null}:
* Add an entry to {coercedValues} named {variableName} with the
value {null}.
* Otherwise:
* If {value} cannot be coerced according to the input coercion
rules of {variableType}, throw a query error.
* Let {coercedValue} be the result of coercing {value} according to the
input coercion rules of {variableType}.
* Add an entry to {coercedValues} named {variableName} with the
value {coercedValue}.
* Return {coercedValues}.

Note: This algorithm is very similar to {CoerceArgumentValues()}.


## Executing Operations

The type system, as described in the "Type System" section of the spec, must
Expand Down Expand Up @@ -591,9 +548,6 @@ CoerceArgumentValues(objectType, field, variableValues):
* If {value} is {null}:
* Add an entry to {coercedValues} named {argumentName} with the
value {null}.
* Otherwise, if {argumentValue} is a {Variable}:
* Add an entry to {coercedValues} named {argumentName} with the
value {value}.
* Otherwise:
* If {value} cannot be coerced according to the input coercion
rules of {variableType}, throw a field error.
Expand All @@ -603,10 +557,6 @@ CoerceArgumentValues(objectType, field, variableValues):
value {coercedValue}.
* Return {coercedValues}.

Note: 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.


### Value Resolution

Expand Down