make EventInfo implement private isDirer interface

So it's possible to mock it in tests.

event.go

@@ -4,7 +4,10 @@
 
 package notify
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 // Event represents the type of filesystem action.
 //
@@ -101,6 +104,18 @@ type EventInfo interface {
 	Sys() interface{} // underlying data source (can return nil)
 }
 
+type isDirer interface {
+	isDir() (bool, error)
+}
+
+var _ fmt.Stringer = (*event)(nil)
+var _ isDirer = (*event)(nil)
+
+// String implements fmt.Stringer interface.
+func (e *event) String() string {
+	return e.Event().String() + `: "` + e.Path() + `"`
+}
+
 var estr = map[Event]string{
 	Create: "notify.Create",
 	Remove: "notify.Remove",
@@ -119,11 +134,6 @@ var estr = map[Event]string{
 	recursive: "recursive",
 }
 
-// String implements fmt.Stringer interface.
-func (e *event) String() string {
-	return e.Event().String() + `: "` + e.Path() + `"`
-}
-
 // Kind gives generic event type of the EventInfo.Event(). The purpose is to
 // hint the notify runtime whether the event created a file or directory or it
 // deleted one. The possible values of Kind are Create or Remove, any other

event_fsevents.go

@@ -67,13 +67,7 @@ type event struct {
 	event Event
 }
 
-func (ei *event) Event() Event     { return ei.event }
-func (ei *event) Path() string     { return ei.fse.Path }
-func (ei *event) Sys() interface{} { return &ei.fse }
-
-func isdir(ei EventInfo) (bool, error) {
-	if ei, ok := ei.(*event); ok {
-		return ei.fse.Flags&FSEventsIsDir != 0, nil
-	}
-	panic("invalid underlying type for the ErrorInfo interface")
-}
+func (ei *event) Event() Event         { return ei.event }
+func (ei *event) Path() string         { return ei.fse.Path }
+func (ei *event) Sys() interface{}     { return &ei.fse }
+func (ei *event) isDir() (bool, error) { return ei.fse.Flags&FSEventsIsDir != 0, nil }

event_inotify.go

@@ -6,10 +6,7 @@
 
 package notify
 
-import (
-	"os"
-	"syscall"
-)
+import "syscall"
 
 // Platform independent event values.
 const (
@@ -78,17 +75,7 @@ type event struct {
 	event Event
 }
 
-func (e *event) Event() Event     { return e.event }
-func (e *event) Path() string     { return e.path }
-func (e *event) Sys() interface{} { return &e.sys }
-
-func isdir(ei EventInfo) (bool, error) {
-	if _, ok := ei.Sys().(syscall.InotifyEvent); ok {
-		return ei.Sys().(syscall.InotifyEvent).Mask&syscall.IN_ISDIR != 0, nil
-	}
-	fi, err := os.Stat(ei.Path())
-	if err != nil {
-		return false, err
-	}
-	return fi.IsDir(), nil
-}
+func (e *event) Event() Event         { return e.event }
+func (e *event) Path() string         { return e.path }
+func (e *event) Sys() interface{}     { return &e.sys }
+func (e *event) isDir() (bool, error) { return e.sys.Mask&syscall.IN_ISDIR != 0, nil }

event_kqueue.go

@@ -86,9 +86,7 @@ func (e *event) Path() string { return e.p }
 // Sys returns platform specific object describing reported event.
 func (e *event) Sys() interface{} { return &e.kq }
 
-func isdir(ei EventInfo) (bool, error) {
-	return ei.Sys().(*Kevent).FI.IsDir(), nil
-}
+func (e *event) isDir() (bool, error) { return e.kq.FI.IsDir(), nil }
 
 // Kevent represents a single event.
 type Kevent struct {

event_readdcw.go

@@ -92,11 +92,11 @@ func (e *event) Event() Event     { return e.e }
 func (e *event) Path() string     { return filepath.Join(syscall.UTF16ToString(e.pathw), e.name) }
 func (e *event) Sys() interface{} { return e.ftype }
 
-func isdir(ei EventInfo) (bool, error) {
-	if ftype, ok := ei.Sys().(uint8); ok && ftype != fTypeUnknown {
-		return ftype == fTypeDirectory, nil
+func (e *event) isDir() (bool, error) {
+	if e.ftype != fTypeUnknown {
+		return e.ftype == fTypeDirectory, nil
 	}
-	fi, err := os.Stat(ei.Path())
+	fi, err := os.Stat(e.Path())
 	if err != nil {
 		return false, err
 	}

event_stub.go

@@ -27,8 +27,7 @@ var ekind = map[Event]Event{}
 
 type event struct{}
 
-func (e *event) Event() (_ Event)     { return }
-func (e *event) Path() (_ string)     { return }
-func (e *event) Sys() (_ interface{}) { return }
-
-func isdir(EventInfo) (_ bool, _ error) { return }
+func (e *event) Event() (_ Event)         { return }
+func (e *event) Path() (_ string)         { return }
+func (e *event) Sys() (_ interface{})     { return }
+func (e *event) isDir() (_ bool, _ error) { return }

watcher_recursive_test.go

@@ -84,7 +84,11 @@ func TestIsDirCreateEvent(t *testing.T) {
 	}
 
 	fn := func(i int, _ WCase, ei EventInfo) error {
-		switch ok, err := isdir(ei); {
+		d, ok := ei.(isDirer)
+		if !ok {
+			return fmt.Errorf("received EventInfo does not implement isDirer")
+		}
+		switch ok, err := d.isDir(); {
 		case err != nil:
 			return err
 		case ok != dirs[i]: