Add 'zero' event

Close #3263

CHANGELOG.md

@@ -3,6 +3,11 @@ CHANGELOG
 
 0.40.0
 ------
+- Added `zero` event that is triggered when there's no match
+  ```sh
+  # Reload the candidate list when there's no match
+  echo $RANDOM | fzf --bind 'zero:reload(echo $RANDOM)+clear-query' --height 3
+  ```
 - New actions
     - Added `track` action which makes fzf track the current item when the
       search result is updated. If the user manually moves the cursor, or the

man/man1/fzf.1

@@ -1008,6 +1008,17 @@ e.g.
      \fB# Automatically select the only match
      seq 10 | fzf --bind one:accept\fR
 .RE
+\fIzero\fR
+.RS
+Triggered when there's no match. \fBzero:abort\fR binding is comparable to
+\fB--exit-0\fR option, but the difference is that \fB--exit-0\fR is only
+effective before the interactive finder starts but \fBzero\fR event is
+triggered by the interactive finder.
+
+e.g.
+     \fB# Reload the candidate list when there's no match
+     echo $RANDOM | fzf --bind 'zero:reload(echo $RANDOM)+clear-query' --height 3\fR
+.RE
 
 \fIbackward-eof\fR
 .RS

src/options.go

@@ -632,6 +632,8 @@ func parseKeyChordsImpl(str string, message string, exit func(string)) map[tui.E
 			add(tui.Focus)
 		case "one":
 			add(tui.One)
+		case "zero":
+			add(tui.Zero)
 		case "alt-enter", "alt-return":
 			chords[tui.CtrlAltKey('m')] = key
 		case "alt-space":

src/terminal.go

@@ -956,10 +956,18 @@ func (t *Terminal) UpdateList(merger *Merger, reset bool) {
 			t.cy = count - util.Min(count, t.maxItems()) + pos
 		}
 	}
-	if !t.reading && t.merger.Length() == 1 {
-		one := tui.One.AsEvent()
-		if _, prs := t.keymap[one]; prs {
-			t.eventChan <- one
+	if !t.reading {
+		switch t.merger.Length() {
+		case 0:
+			zero := tui.Zero.AsEvent()
+			if _, prs := t.keymap[zero]; prs {
+				t.eventChan <- zero
+			}
+		case 1:
+			one := tui.One.AsEvent()
+			if _, prs := t.keymap[one]; prs {
+				t.eventChan <- one
+			}
 		}
 	}
 	t.mutex.Unlock()
@@ -2854,7 +2862,7 @@ func (t *Terminal) Loop() {
 			}
 			select {
 			case event = <-t.eventChan:
-				needBarrier = event != tui.Load.AsEvent()
+				needBarrier = !event.Is(tui.Load, tui.One, tui.Zero)
 			case actions = <-t.serverChan:
 				event = tui.Invalid.AsEvent()
 				needBarrier = false

src/tui/tui.go

@@ -94,6 +94,7 @@ const (
 	Load
 	Focus
 	One
+	Zero
 
 	AltBS
 
@@ -283,6 +284,15 @@ type Event struct {
 	MouseEvent *MouseEvent
 }
 
+func (e Event) Is(types ...EventType) bool {
+	for _, t := range types {
+		if e.Type == t {
+			return true
+		}
+	}
+	return false
+}
+
 type MouseEvent struct {
 	Y      int
 	X      int

test/test_go.rb

@@ -2835,18 +2835,24 @@ class TestGoFZF < TestBase
     end
   end
 
-  def test_one
-    tmux.send_keys "seq 10 | #{FZF} --bind 'one:preview:echo {} is the only match'", :Enter
+  def test_one_and_zero
+    tmux.send_keys "seq 10 | #{FZF} --bind 'zero:preview(echo no match),one:preview(echo {} is the only match)'", :Enter
     tmux.send_keys '1'
     tmux.until do |lines|
       assert_equal 2, lines.match_count
       refute(lines.any? { _1.include?('only match') })
+      refute(lines.any? { _1.include?('no match') })
     end
     tmux.send_keys '0'
     tmux.until do |lines|
       assert_equal 1, lines.match_count
       assert(lines.any? { _1.include?('only match') })
     end
+    tmux.send_keys '0'
+    tmux.until do |lines|
+      assert_equal 0, lines.match_count
+      assert(lines.any? { _1.include?('no match') })
+    end
   end
 
   def test_height_range_with_exit_0