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package matchers
import (
"fmt"
"reflect"
"github.com/onsi/gomega/types"
)
type WithTransformMatcher struct {
// input
Transform interface{} // must be a function of one parameter that returns one value and an optional error
Matcher types.GomegaMatcher
// cached value
transformArgType reflect.Type
// state
transformedValue interface{}
}
// reflect.Type for error
var errorT = reflect.TypeOf((*error)(nil)).Elem()
func NewWithTransformMatcher(transform interface{}, matcher types.GomegaMatcher) *WithTransformMatcher {
if transform == nil {
panic("transform function cannot be nil")
}
txType := reflect.TypeOf(transform)
if txType.NumIn() != 1 {
panic("transform function must have 1 argument")
}
if numout := txType.NumOut(); numout != 1 {
if numout != 2 || !txType.Out(1).AssignableTo(errorT) {
panic("transform function must either have 1 return value, or 1 return value plus 1 error value")
}
}
return &WithTransformMatcher{
Transform: transform,
Matcher: matcher,
transformArgType: reflect.TypeOf(transform).In(0),
}
}
func (m *WithTransformMatcher) Match(actual interface{}) (bool, error) {
// prepare a parameter to pass to the Transform function
var param reflect.Value
if actual != nil && reflect.TypeOf(actual).AssignableTo(m.transformArgType) {
// The dynamic type of actual is compatible with the transform argument.
param = reflect.ValueOf(actual)
} else if actual == nil && m.transformArgType.Kind() == reflect.Interface {
// The dynamic type of actual is unknown, so there's no way to make its
// reflect.Value. Create a nil of the transform argument, which is known.
param = reflect.Zero(m.transformArgType)
} else {
return false, fmt.Errorf("Transform function expects '%s' but we have '%T'", m.transformArgType, actual)
}
// call the Transform function with `actual`
fn := reflect.ValueOf(m.Transform)
result := fn.Call([]reflect.Value{param})
if len(result) == 2 {
if !result[1].IsNil() {
return false, fmt.Errorf("Transform function failed: %s", result[1].Interface().(error).Error())
}
}
m.transformedValue = result[0].Interface() // expect exactly one value
return m.Matcher.Match(m.transformedValue)
}
func (m *WithTransformMatcher) FailureMessage(_ interface{}) (message string) {
return m.Matcher.FailureMessage(m.transformedValue)
}
func (m *WithTransformMatcher) NegatedFailureMessage(_ interface{}) (message string) {
return m.Matcher.NegatedFailureMessage(m.transformedValue)
}
func (m *WithTransformMatcher) MatchMayChangeInTheFuture(_ interface{}) bool {
// TODO: Maybe this should always just return true? (Only an issue for non-deterministic transformers.)
//
// Querying the next matcher is fine if the transformer always will return the same value.
// But if the transformer is non-deterministic and returns a different value each time, then there
// is no point in querying the next matcher, since it can only comment on the last transformed value.
return types.MatchMayChangeInTheFuture(m.Matcher, m.transformedValue)
}
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