filewatcher: fix event.Op comparison

Previously it was matching all events, which caused problems in editors
like vim, which rename the file. It seemed to be running before the file
was finished writing.

internal/filewatcher/watch.go

@@ -38,6 +38,9 @@ func Watch(dirs []string, run func(pkg string) error) error {
 		case <-timer.C:
 			return fmt.Errorf("exceeded idle timeout while watching files")
 		case event := <-watcher.Events:
+			if !timer.Stop() {
+				<-timer.C
+			}
 			log.Debugf("handling event %v", event)
 
 			if handleDirCreated(watcher, event) {
@@ -129,7 +132,7 @@ func noGoFiles(path string) bool {
 	}
 }
 
-func handleDirCreated(watcher *fsnotify.Watcher, event fsnotify.Event) bool {
+func handleDirCreated(watcher *fsnotify.Watcher, event fsnotify.Event) (handled bool) {
 	if event.Op&fsnotify.Create != fsnotify.Create {
 		return false
 	}
@@ -158,7 +161,7 @@ type handler struct {
 const floodThreshold = 250 * time.Millisecond
 
 func (h *handler) handleEvent(event fsnotify.Event) error {
-	if event.Op&fsnotify.Write|fsnotify.Create == 0 {
+	if event.Op&(fsnotify.Write|fsnotify.Create) == 0 {
 		return nil
 	}
 

internal/filewatcher/watch_test.go

@@ -0,0 +1,78 @@
+package filewatcher
+
+import (
+	"testing"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"gotest.tools/v3/assert"
+)
+
+func TestHandler_HandleEvent(t *testing.T) {
+	type testCase struct {
+		name        string
+		last        time.Time
+		expectedRun bool
+		event       fsnotify.Event
+	}
+
+	fn := func(t *testing.T, tc testCase) {
+		var ran bool
+		run := func(pkg string) error {
+			ran = true
+			return nil
+		}
+
+		h := handler{last: tc.last, fn: run}
+		err := h.handleEvent(tc.event)
+		assert.NilError(t, err)
+		assert.Equal(t, ran, tc.expectedRun)
+		if tc.expectedRun {
+			assert.Assert(t, !h.last.IsZero())
+		}
+	}
+
+	var testCases = []testCase{
+		{
+			name:  "Op is rename",
+			event: fsnotify.Event{Op: fsnotify.Rename, Name: "file_test.go"},
+		},
+		{
+			name:  "Op is remove",
+			event: fsnotify.Event{Op: fsnotify.Remove, Name: "file_test.go"},
+		},
+		{
+			name:  "Op is chmod",
+			event: fsnotify.Event{Op: fsnotify.Chmod, Name: "file_test.go"},
+		},
+		{
+			name:        "Op is write+chmod",
+			event:       fsnotify.Event{Op: fsnotify.Write | fsnotify.Chmod, Name: "file_test.go"},
+			expectedRun: true,
+		},
+		{
+			name:        "Op is write",
+			event:       fsnotify.Event{Op: fsnotify.Write, Name: "file_test.go"},
+			expectedRun: true,
+		},
+		{
+			name:        "Op is create",
+			event:       fsnotify.Event{Op: fsnotify.Create, Name: "file_test.go"},
+			expectedRun: true,
+		},
+		{
+			name:  "file is not a go file",
+			event: fsnotify.Event{Op: fsnotify.Write, Name: "readme.md"},
+		},
+		{
+			name:  "under flood threshold",
+			event: fsnotify.Event{Op: fsnotify.Create, Name: "file_test.go"},
+			last:  time.Now(),
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			fn(t, tc)
+		})
+	}
+}