Function CompleteValue

graphql/schema/completion.go:176–236

CompleteValue applies the value completion algorithm to a single value, which could turn out to be a list or object or scalar value.

(
	path []interface{},
	field Field,
	val interface{})

// CompleteValue applies the value completion algorithm to a single value, which
// could turn out to be a list or object or scalar value.
func CompleteValue(
	path []interface{},
	field Field,
	val interface{}) ([]byte, x.GqlErrorList) {

	switch val := val.(type) {
	case map[string]interface{}:
		switch field.Type().Name() {
		case "String", "ID", "Boolean", "Float", "Int", "Int64", "DateTime":
			return nil, x.GqlErrorList{field.GqlErrorf(path, ErrExpectedScalar)}
		}
		enumValues := field.EnumValues()
		if len(enumValues) > 0 {
			return nil, x.GqlErrorList{field.GqlErrorf(path, ErrExpectedScalar)}
		}
		return CompleteObject(path, field.SelectionSet(), val)
	case []interface{}:
		return completeList(path, field, val)
	case []map[string]interface{}:
		// This case is different from the []interface{} case above and is true for admin queries
		// where we built the val ourselves.
		listVal := make([]interface{}, 0, len(val))
		for _, v := range val {
			listVal = append(listVal, v)
		}
		return completeList(path, field, listVal)
	default:
		if val == nil {
			if b := field.NullValue(); b != nil {
				return b, nil
			}

			return nil, x.GqlErrorList{field.GqlErrorf(path, ErrExpectedNonNull,
				field.Name(), field.Type())}
		}

		// val is a scalar
		val, gqlErr := coerceScalar(val, field, path)
		if len(gqlErr) > 0 {
			return nil, gqlErr
		}

		// Can this ever error?  We can't have an unsupported type or value because
		// we just unmarshalled this val.
		b, err := json.Marshal(val)
		if err != nil {
			gqlErr := x.GqlErrorList{field.GqlErrorf(path,
				"Error marshalling value for field '%s' (type %s).  "+
					"Resolved as null (which may trigger GraphQL error propagation) ",
				field.Name(), field.Type())}

			if field.Type().Nullable() {
				return JsonNull, gqlErr
			}

			return nil, gqlErr
		}