From 5961f3201e574dd8836721a9ea6e61b36a10d59d Mon Sep 17 00:00:00 2001
From: Daisuke Maki <lestrrat+github@gmail.com>
Date: Mon, 15 Aug 2022 10:55:30 +0900
Subject: [PATCH] Implement --on-empty=exit

---
 interface.go |  6 ++++++
 peco.go      | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/interface.go b/interface.go
index ec2ea3e..80a030c 100644
--- a/interface.go
+++ b/interface.go
@@ -52,6 +52,10 @@ const (
 	RegexpMatch        = "Regexp"
 )
 
+const (
+	OnEmptyExit = `exit`
+)
+
 type idgen struct {
 	ch chan uint64
 }
@@ -84,6 +88,7 @@ type Peco struct {
 	maxScanBufferSize       int
 	mutex                   sync.Mutex
 	onCancel                string
+	onEmpty                 string
 	printQuery              bool
 	prompt                  string
 	query                   Query
@@ -411,6 +416,7 @@ type CLIOptions struct {
 	OptInitialFilter   string `long:"initial-filter" description:"specify the default filter"`
 	OptPrompt          string `long:"prompt" description:"specify the prompt string"`
 	OptLayout          string `long:"layout" description:"layout to be used. 'top-down' or 'bottom-up'. default is 'top-down'"`
+	OptOnEmpty         string `long:"on-empty" description:"action to take when the input is finite (not a stream) and the buffer is empty. specify 'exit' to exit peco when the buffer is empty"`
 	OptSelect1         bool   `long:"select-1" description:"select first item and immediately exit if the input contains only 1 item"`
 	OptOnCancel        string `long:"on-cancel" description:"specify action on user cancel. 'success' or 'error'.\ndefault is 'success'. This may change in future versions"`
 	OptSelectionPrefix string `long:"selection-prefix" description:"use a prefix instead of changing line color to indicate currently selected lines.\ndefault is to use colors. This option is experimental"`
diff --git a/peco.go b/peco.go
index 966d2be..980a79e 100644
--- a/peco.go
+++ b/peco.go
@@ -311,6 +311,12 @@ func (p *Peco) selectOneAndExitIfPossible() {
 	}
 }
 
+func (p *Peco) exitOnEmpty() {
+	if b := p.CurrentLineBuffer(); b.Size() == 0 {
+		p.Exit(errCollectResults{})
+	}
+}
+
 func (p *Peco) Run(ctx context.Context) (err error) {
 	if pdebug.Enabled {
 		g := pdebug.Marker("Peco.Run").BindError(&err)
@@ -393,6 +399,18 @@ func (p *Peco) Run(ctx context.Context) (err error) {
 		}()
 	}
 
+	if !src.IsInfinite() {
+		switch p.onEmpty {
+		case OnEmptyExit:
+			go func() {
+				<-p.source.SetupDone()
+				p.exitOnEmpty()
+			}()
+		default:
+			// DO NOTHING
+		}
+	}
+
 	readyOnce.Do(func() { close(p.readyCh) })
 
 	// This has tobe AFTER close(p.readyCh), otherwise the query is
@@ -558,6 +576,12 @@ func (p *Peco) ApplyConfig(opts CLIOptions) error {
 	} else {
 		p.selectionPrefix = p.config.SelectionPrefix
 	}
+	switch opts.OptOnEmpty {
+	case OnEmptyExit, "":
+	default:
+		return errors.Errorf("invalid --on-empty value %q", opts.OptOnEmpty)
+	}
+	p.onEmpty = opts.OptOnEmpty
 	p.selectOneAndExit = opts.OptSelect1
 	p.printQuery = opts.OptPrintQuery
 	p.initialQuery = opts.OptQuery