Add 'one' event

Close #2629
Close #2494
Close #459

CHANGELOG.md

@@ -3,6 +3,11 @@ CHANGELOG
 
 0.39.0
 ------
+- Added `one` event that is triggered when there's only one match
+  ```sh
+  # Automatically select the only match
+  seq 10 | fzf --bind one:accept
+  ```
 - Added `--track` option that makes fzf track the current selection when the
   result list is updated. This can be useful when browsing logs using fzf with
   sorting disabled.

man/man1/fzf.1

@@ -993,6 +993,17 @@ e.g.
      # Beware not to introduce an infinite loop
      seq 10 | fzf --bind 'focus:up' --cycle\fR
 .RE
+\fIone\fR
+.RS
+Triggered when there's only one match. \fBone:accept\fR binding is comparable
+to \fB--select-1\fR option, but the difference is that \fB--select-1\fR is only
+effective before the interactive finder starts but \fBone\fR event is triggered
+by the interactive finder.
+
+e.g.
+     \fB# Automatically select the only match
+     seq 10 | fzf --bind one:accept\fR
+.RE
 
 \fIbackward-eof\fR
 .RS

src/options.go

@@ -622,6 +622,8 @@ func parseKeyChordsImpl(str string, message string, exit func(string)) map[tui.E
 			add(tui.Load)
 		case "focus":
 			add(tui.Focus)
+		case "one":
+			add(tui.One)
 		case "alt-enter", "alt-return":
 			chords[tui.CtrlAltKey('m')] = key
 		case "alt-space":

src/terminal.go

@@ -932,6 +932,12 @@ 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
+		}
+	}
 	t.mutex.Unlock()
 	t.reqBox.Set(reqInfo, nil)
 	t.reqBox.Set(reqList, nil)

src/tui/tui.go

@@ -93,6 +93,7 @@ const (
 	Start
 	Load
 	Focus
+	One
 
 	AltBS
 

test/test_go.rb

@@ -2702,6 +2702,20 @@ class TestGoFZF < TestBase
       assert_equal '> 555', lines[index]
     end
   end
+
+  def test_one
+    tmux.send_keys "seq 10 | #{FZF} --bind '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') }
+    end
+    tmux.send_keys '0'
+    tmux.until do |lines|
+      assert_equal 1, lines.match_count
+      assert lines.any? { _1.include?('only match') }
+    end
+  end
 end
 
 module TestShell