WithTransform() supports transform function with explicit types
diff --git a/matchers.go b/matchers.go
index 872de9e..ba41103 100644
--- a/matchers.go
+++ b/matchers.go
@@ -371,13 +371,11 @@
}
//WithTransform applies the `transform` to the actual value and matches it against `matcher`.
-// var plus1 = func(i interface{}) interface{} { return i.(int) + 1 }
+//The given transform must be a function of one parameter that returns one value.
+// var plus1 = func(i int) int { return i + 1 }
// Expect(1).To(WithTransform(plus1, Equal(2))
//
//And(), Or(), Not() and WithTransform() allow matchers to be composed into complex expressions.
-func WithTransform(transform func(interface{}) interface{}, matcher types.GomegaMatcher) types.GomegaMatcher {
- return &matchers.WithTransformMatcher{
- Transform: transform,
- Matcher: matcher,
- }
+func WithTransform(transform interface{}, matcher types.GomegaMatcher) types.GomegaMatcher {
+ return matchers.NewWithTransformMatcher(transform, matcher)
}
diff --git a/matchers/with_transform.go b/matchers/with_transform.go
index c7a650a..430223e 100644
--- a/matchers/with_transform.go
+++ b/matchers/with_transform.go
@@ -1,25 +1,61 @@
package matchers
-import "github.com/onsi/gomega/types"
+import (
+ "fmt"
+ "github.com/onsi/gomega/types"
+ "reflect"
+)
type WithTransformMatcher struct {
// input
- Transform func(interface{}) interface{}
+ Transform interface{} // must be a function of one parameter that returns one value
Matcher types.GomegaMatcher
+ // cached value
+ transformArgType reflect.Type
+
// state
transformedValue interface{}
}
+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 txType.NumOut() != 1 {
+ panic("transform function must have 1 return value")
+ }
+
+ return &WithTransformMatcher{
+ Transform: transform,
+ Matcher: matcher,
+ transformArgType: reflect.TypeOf(transform).In(0),
+ }
+}
+
func (m *WithTransformMatcher) Match(actual interface{}) (bool, error) {
- m.transformedValue = m.Transform(actual)
+ // return error if actual's type is incompatible with Transform function's argument type
+ actualType := reflect.TypeOf(actual)
+ if !actualType.AssignableTo(m.transformArgType) {
+ return false, fmt.Errorf("Transform function expects '%s' but we have '%s'", m.transformArgType, actualType)
+ }
+
+ // call the Transform function with `actual`
+ fn := reflect.ValueOf(m.Transform)
+ result := fn.Call([]reflect.Value{reflect.ValueOf(actual)})
+ m.transformedValue = result[0].Interface() // expect exactly one value
+
return m.Matcher.Match(m.transformedValue)
}
-func (m *WithTransformMatcher) FailureMessage(actual interface{}) (message string) {
+func (m *WithTransformMatcher) FailureMessage(_ interface{}) (message string) {
return m.Matcher.FailureMessage(m.transformedValue)
}
-func (m *WithTransformMatcher) NegatedFailureMessage(actual interface{}) (message string) {
+func (m *WithTransformMatcher) NegatedFailureMessage(_ interface{}) (message string) {
return m.Matcher.NegatedFailureMessage(m.transformedValue)
}
diff --git a/matchers/with_transform_test.go b/matchers/with_transform_test.go
index ced53bd..4d1a363 100644
--- a/matchers/with_transform_test.go
+++ b/matchers/with_transform_test.go
@@ -1,18 +1,56 @@
package matchers_test
import (
+ "errors"
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)
var _ = Describe("WithTransformMatcher", func() {
- var plus1 = func(i interface{}) interface{} { return i.(int) + 1 }
+ var plus1 = func(i int) int { return i + 1 }
+
+ Context("Panic if transform function invalid", func() {
+ panicsWithTransformer := func(transform interface{}) {
+ ExpectWithOffset(1, func() { WithTransform(transform, nil) }).To(Panic())
+ }
+ It("nil", func() {
+ panicsWithTransformer(nil)
+ })
+ Context("Invalid number of args, but correct return value count", func() {
+ It("zero", func() {
+ panicsWithTransformer(func() int { return 5 })
+ })
+ It("two", func() {
+ panicsWithTransformer(func(i, j int) int { return 5 })
+ })
+ })
+ Context("Invalid number of return values, but correct number of arguments", func() {
+ It("zero", func() {
+ panicsWithTransformer(func(i int) {})
+ })
+ It("two", func() {
+ panicsWithTransformer(func(i int) (int, int) { return 5, 6 })
+ })
+ })
+ })
It("works with positive cases", func() {
Expect(1).To(WithTransform(plus1, Equal(2)))
Expect(1).To(WithTransform(plus1, WithTransform(plus1, Equal(3))))
Expect(1).To(WithTransform(plus1, And(Equal(2), BeNumerically(">", 1))))
+
+ // transform expects custom type
+ type S struct {
+ A int
+ B string
+ }
+ transformer := func(s S) string { return s.B }
+ Expect(S{1, "hi"}).To(WithTransform(transformer, Equal("hi")))
+
+ // transform expects interface
+ errString := func(e error) string { return e.Error() }
+ Expect(errors.New("abc")).To(WithTransform(errString, Equal("abc")))
})
It("works with negative cases", func() {
@@ -25,7 +63,7 @@
It("gives a descriptive message", func() {
m := WithTransform(plus1, Equal(3))
Expect(m.Match(1)).To(BeFalse())
- Expect(m.FailureMessage(input)).To(Equal("Expected\n <int>: 2\nto equal\n <int>: 3"))
+ Expect(m.FailureMessage(1)).To(Equal("Expected\n <int>: 2\nto equal\n <int>: 3"))
})
})
@@ -33,7 +71,16 @@
It("gives a descriptive message", func() {
m := Not(WithTransform(plus1, Equal(3)))
Expect(m.Match(2)).To(BeFalse())
- Expect(m.FailureMessage(input)).To(Equal("Expected\n <int>: 3\nnot to equal\n <int>: 3"))
+ Expect(m.FailureMessage(2)).To(Equal("Expected\n <int>: 3\nnot to equal\n <int>: 3"))
+ })
+ })
+
+ Context("actual value is incompatible with transform function's argument type", func() {
+ It("gracefully fails if transform cannot be performed", func() {
+ m := WithTransform(plus1, Equal(3))
+ result, err := m.Match("hi") // give it a string but transform expects int; doesn't panic
+ Expect(result).To(BeFalse())
+ Expect(err).To(MatchError("Transform function expects 'int' but we have 'string'"))
})
})
})
