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