1package matchers
 2
 3import (
 4	"fmt"
 5	"reflect"
 6
 7	"github.com/onsi/gomega/internal/oraclematcher"
 8	"github.com/onsi/gomega/types"
 9)
10
11type WithTransformMatcher struct {
12	// input
13	Transform interface{} // must be a function of one parameter that returns one value
14	Matcher   types.GomegaMatcher
15
16	// cached value
17	transformArgType reflect.Type
18
19	// state
20	transformedValue interface{}
21}
22
23func NewWithTransformMatcher(transform interface{}, matcher types.GomegaMatcher) *WithTransformMatcher {
24	if transform == nil {
25		panic("transform function cannot be nil")
26	}
27	txType := reflect.TypeOf(transform)
28	if txType.NumIn() != 1 {
29		panic("transform function must have 1 argument")
30	}
31	if txType.NumOut() != 1 {
32		panic("transform function must have 1 return value")
33	}
34
35	return &WithTransformMatcher{
36		Transform:        transform,
37		Matcher:          matcher,
38		transformArgType: reflect.TypeOf(transform).In(0),
39	}
40}
41
42func (m *WithTransformMatcher) Match(actual interface{}) (bool, error) {
43	// prepare a parameter to pass to the Transform function
44	var param reflect.Value
45	if actual != nil && reflect.TypeOf(actual).AssignableTo(m.transformArgType) {
46		// The dynamic type of actual is compatible with the transform argument.
47		param = reflect.ValueOf(actual)
48
49	} else if actual == nil && m.transformArgType.Kind() == reflect.Interface {
50		// The dynamic type of actual is unknown, so there's no way to make its
51		// reflect.Value. Create a nil of the transform argument, which is known.
52		param = reflect.Zero(m.transformArgType)
53
54	} else {
55		return false, fmt.Errorf("Transform function expects '%s' but we have '%T'", m.transformArgType, actual)
56	}
57
58	// call the Transform function with `actual`
59	fn := reflect.ValueOf(m.Transform)
60	result := fn.Call([]reflect.Value{param})
61	m.transformedValue = result[0].Interface() // expect exactly one value
62
63	return m.Matcher.Match(m.transformedValue)
64}
65
66func (m *WithTransformMatcher) FailureMessage(_ interface{}) (message string) {
67	return m.Matcher.FailureMessage(m.transformedValue)
68}
69
70func (m *WithTransformMatcher) NegatedFailureMessage(_ interface{}) (message string) {
71	return m.Matcher.NegatedFailureMessage(m.transformedValue)
72}
73
74func (m *WithTransformMatcher) MatchMayChangeInTheFuture(_ interface{}) bool {
75	// TODO: Maybe this should always just return true? (Only an issue for non-deterministic transformers.)
76	//
77	// Querying the next matcher is fine if the transformer always will return the same value.
78	// But if the transformer is non-deterministic and returns a different value each time, then there
79	// is no point in querying the next matcher, since it can only comment on the last transformed value.
80	return oraclematcher.MatchMayChangeInTheFuture(m.Matcher, m.transformedValue)
81}