Fix error when preview command failed to start

src/terminal.go

@@ -1855,13 +1855,9 @@ func (t *Terminal) Loop() {
 					reader := bufio.NewReader(out)
 					eofChan := make(chan bool)
 					finishChan := make(chan bool, 1)
-					reapChan := make(chan bool)
 					err := cmd.Start()
-					reaps := 0
-					if err != nil {
-						t.reqBox.Set(reqPreviewDisplay, previewResult{version, []string{err.Error()}, 0, ""})
-					} else {
-						reaps = 2
+					if err == nil {
+						reapChan := make(chan bool)
 						lineChan := make(chan eachLine)
 						// Goroutine 1 reads process output
 						go func() {
@@ -1874,6 +1870,7 @@ func (t *Terminal) Loop() {
 							}
 							eofChan <- true
 						}()
+
 						// Goroutine 2 periodically requests rendering
 						go func(version int64) {
 							lines := []string{}
@@ -1915,7 +1912,7 @@ func (t *Terminal) Loop() {
 							ticker.Stop()
 							reapChan <- true
 						}(version)
-					}
+
 						// Goroutine 3 is responsible for cancelling running preview command
 						go func(version int64) {
 							timer := time.NewTimer(previewDelayed)
@@ -1945,12 +1942,17 @@ func (t *Terminal) Loop() {
 							timer.Stop()
 							reapChan <- true
 						}(version)
-					<-eofChan
+
+						<-eofChan          // Goroutine 1 finished
 						cmd.Wait()         // NOTE: We should not call Wait before EOF
-					finishChan <- true
-					for i := 0; i < reaps; i++ {
+						finishChan <- true // Tell Goroutine 3 to stop
+						<-reapChan         // Goroutine 2 and 3 finished
 						<-reapChan
+					} else {
+						// Failed to start the command. Report the error immediately.
+						t.reqBox.Set(reqPreviewDisplay, previewResult{version, []string{err.Error()}, 0, ""})
 					}
+
 					cleanTemporaryFiles()
 				} else {
 					t.reqBox.Set(reqPreviewDisplay, previewResult{version, nil, 0, ""})