Print [ERROR] on info line when the default command failed

With zero result.

Related: https://github.com/junegunn/fzf.vim/issues/22#issuecomment-311869805

src/core.go

@@ -228,7 +228,7 @@ func Run(opts *Options, revision string) {
 				case EvtReadNew, EvtReadFin:
 					reading = reading && evt == EvtReadNew
 					snapshot, count := chunkList.Snapshot()
-					terminal.UpdateCount(count, !reading)
+					terminal.UpdateCount(count, !reading, value.(bool))
 					matcher.Reset(snapshot, terminal.Input(), false, !reading, sort)
 
 				case EvtSearchNew:

src/reader.go

@@ -17,16 +17,17 @@ type Reader struct {
 
 // ReadSource reads data from the default command or from standard input
 func (r *Reader) ReadSource() {
+	var success bool
 	if util.IsTty() {
 		cmd := os.Getenv("FZF_DEFAULT_COMMAND")
 		if len(cmd) == 0 {
 			cmd = defaultCommand
 		}
-		r.readFromCommand(cmd)
+		success = r.readFromCommand(cmd)
 	} else {
-		r.readFromStdin()
+		success = r.readFromStdin()
 	}
-	r.eventBox.Set(EvtReadFin, nil)
+	r.eventBox.Set(EvtReadFin, success)
 }
 
 func (r *Reader) feed(src io.Reader) {
@@ -50,7 +51,7 @@ func (r *Reader) feed(src io.Reader) {
 				}
 			}
 			if r.pusher(bytea) {
-				r.eventBox.Set(EvtReadNew, nil)
+				r.eventBox.Set(EvtReadNew, true)
 			}
 		}
 		if err != nil {
@@ -59,20 +60,21 @@ func (r *Reader) feed(src io.Reader) {
 	}
 }
 
-func (r *Reader) readFromStdin() {
+func (r *Reader) readFromStdin() bool {
 	r.feed(os.Stdin)
+	return true
 }
 
-func (r *Reader) readFromCommand(cmd string) {
+func (r *Reader) readFromCommand(cmd string) bool {
 	listCommand := util.ExecCommand(cmd)
 	out, err := listCommand.StdoutPipe()
 	if err != nil {
-		return
+		return false
 	}
 	err = listCommand.Start()
 	if err != nil {
-		return
+		return false
 	}
-	defer listCommand.Wait()
 	r.feed(out)
+	return listCommand.Wait() == nil
 }

src/terminal.go

@@ -94,6 +94,7 @@ type Terminal struct {
 	count      int
 	progress   int
 	reading    bool
+	success    bool
 	jumping    jumpMode
 	jumpLabels string
 	printer    func(string)
@@ -372,6 +373,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		ansi:       opts.Ansi,
 		tabstop:    opts.Tabstop,
 		reading:    true,
+		success:    true,
 		jumping:    jumpDisabled,
 		jumpLabels: opts.JumpLabels,
 		printer:    opts.Printer,
@@ -401,10 +403,11 @@ func (t *Terminal) Input() []rune {
 }
 
 // UpdateCount updates the count information
-func (t *Terminal) UpdateCount(cnt int, final bool) {
+func (t *Terminal) UpdateCount(cnt int, final bool, success bool) {
 	t.mutex.Lock()
 	t.count = cnt
 	t.reading = !final
+	t.success = success
 	t.mutex.Unlock()
 	t.reqBox.Set(reqInfo, nil)
 	if final {
@@ -682,6 +685,9 @@ func (t *Terminal) printInfo() {
 	if t.progress > 0 && t.progress < 100 {
 		output += fmt.Sprintf(" (%d%%)", t.progress)
 	}
+	if !t.success && t.count == 0 {
+		output += " [ERROR]"
+	}
 	if pos+len(output) <= t.window.Width() {
 		t.window.CPrint(tui.ColInfo, 0, output)
 	}

test/test_go.rb

@@ -260,6 +260,12 @@ class TestGoFZF < TestBase
     assert_equal 'hello', readonce.chomp
   end
 
+  def test_fzf_default_command_failure
+    tmux.send_keys fzf.sub('FZF_DEFAULT_COMMAND=', 'FZF_DEFAULT_COMMAND=false'), :Enter
+    tmux.until { |lines| lines[-2].include?('ERROR') }
+    tmux.send_keys :Enter
+  end
+
   def test_key_bindings
     tmux.send_keys "#{FZF} -q 'foo bar foo-bar'", :Enter
     tmux.until { |lines| lines.last =~ /^>/ }