Merge pull request gotestyourself#43 from dnephin/handle-unexported-p…

…anic

Handle go-cmp panic on unexported

assert/cmp/compare.go

@@ -15,12 +15,32 @@ import (
 //
 // The comparison can be customized using comparison Options.
 func Compare(x, y interface{}, opts ...cmp.Option) func() (bool, string) {
-	return func() (bool, string) {
+	return func() (success bool, msg string) {
+		defer func() {
+			if panicmsg, handled := handleCmpPanic(recover()); handled {
+				msg = panicmsg
+			}
+		}()
 		diff := cmp.Diff(x, y, opts...)
 		return diff == "", "\n" + diff
 	}
 }
 
+func handleCmpPanic(r interface{}) (string, bool) {
+	if r == nil {
+		return "", false
+	}
+	panicmsg, ok := r.(string)
+	if !ok {
+		panic(r)
+	}
+	switch {
+	case strings.HasPrefix(panicmsg, "cannot handle unexported field"):
+		return panicmsg, true
+	}
+	panic(r)
+}
+
 // Equal succeeds if x == y.
 func Equal(x, y interface{}) func() (success bool, message string) {
 	return func() (bool, string) {

assert/cmp/compare_test.go

@@ -10,6 +10,28 @@ import (
 	"github.com/pkg/errors"
 )
 
+func TestCompare(t *testing.T) {
+	success, msg := Compare([]string{"a", "b"}, []string{"b", "a"})()
+	assertFailure(t, success, msg, `
+{[]string}:
+	-: []string{"a", "b"}
+	+: []string{"b", "a"}
+`)
+
+	success, msg = Compare([]string{"a"}, []string{"a"})()
+	assertSuccess(t, success, msg)
+}
+
+type Stub struct {
+	unx int
+}
+
+func TestCompareWithUnexported(t *testing.T) {
+	success, msg := Compare(Stub{}, Stub{unx: 1})()
+	assertFailure(t, success, msg, `cannot handle unexported field: {cmp.Stub}.unx
+consider using AllowUnexported or cmpopts.IgnoreUnexported`)
+}
+
 func TestLen(t *testing.T) {
 	var testcases = []struct {
 		seq             interface{}