Add transform-prompt(...) action

CHANGELOG.md

@@ -56,6 +56,13 @@ CHANGELOG
       ```sh
       curl localhost:6266 -d "change-query:$(date)"
       ```
+    - Added `transform-prompt(...)` action for transforming the prompt string
+      using an external command
+      ```sh
+      # Press space to change the prompt string using an external command
+      # (only the first line of the output is taken)
+      fzf --bind 'space:reload(ls),load:transform-prompt(printf "%s> " "$(date)")'
+      ```
     - Added `transform-query(...)` action for transforming the query string using
       an external command
       ```sh

man/man1/fzf.1

@@ -1034,6 +1034,7 @@ A key or an event can be bound to one or more of the following actions.
     \fBtoggle-search\fR              (toggle search functionality)
     \fBtoggle-sort\fR
     \fBtoggle+up\fR                  \fIbtab    (shift-tab)\fR
+    \fBtransform-prompt(...)\fR      (transform prompt string using an external command)
     \fBtransform-query(...)\fR       (transform query string using an external command)
     \fBunbind(...)\fR                (unbind bindings)
     \fBunix-line-discard\fR          \fIctrl-u\fR

src/options.go

@@ -892,7 +892,7 @@ const (
 
 func init() {
 	executeRegexp = regexp.MustCompile(
-		`(?si)[:+](execute(?:-multi|-silent)?|reload(?:-sync)?|preview|change-query|change-prompt|change-preview-window|change-preview|(?:re|un)bind|pos|put|transform-query)`)
+		`(?si)[:+](execute(?:-multi|-silent)?|reload(?:-sync)?|preview|(?:change|transform)-(?:query|prompt)|change-preview-window|change-preview|(?:re|un)bind|pos|put)`)
 	splitRegexp = regexp.MustCompile("[,:]+")
 	actionNameRegexp = regexp.MustCompile("(?i)^[a-z-]+")
 }
@@ -1211,6 +1211,8 @@ func isExecuteAction(str string) actionType {
 		return actExecuteMulti
 	case "put":
 		return actPut
+	case "transform-prompt":
+		return actTransformPrompt
 	case "transform-query":
 		return actTransformQuery
 	}

src/terminal.go

@@ -311,6 +311,7 @@ const (
 	actToggleSort
 	actTogglePreview
 	actTogglePreviewWrap
+	actTransformPrompt
 	actTransformQuery
 	actPreview
 	actChangePreview
@@ -2034,8 +2035,10 @@ func (t *Terminal) redraw(clear bool) {
 
 func (t *Terminal) executeCommand(template string, forcePlus bool, background bool, captureFirstLine bool) string {
 	line := ""
-	valid, list := t.buildPlusList(template, forcePlus)
-	if !valid {
+	valid, list := t.buildPlusList(template, forcePlus, false)
+	// captureFirstLine is used for transform-{prompt,query} and we don't want to
+	// return an empty string in those cases
+	if !valid && !captureFirstLine {
 		return line
 	}
 	command := t.replacePlaceholder(template, forcePlus, string(t.input), list)
@@ -2093,10 +2096,10 @@ func (t *Terminal) currentItem() *Item {
 	return nil
 }
 
-func (t *Terminal) buildPlusList(template string, forcePlus bool) (bool, []*Item) {
+func (t *Terminal) buildPlusList(template string, forcePlus bool, forceEvaluation bool) (bool, []*Item) {
 	current := t.currentItem()
 	slot, plus, query := hasPreviewFlags(template)
-	if !(!slot || query || (forcePlus || plus) && len(t.selected) > 0) {
+	if !forceEvaluation && !(!slot || query || (forcePlus || plus) && len(t.selected) > 0) {
 		return current != nil, []*Item{current, current}
 	}
 
@@ -2421,7 +2424,7 @@ func (t *Terminal) Loop() {
 
 	refreshPreview := func(command string) {
 		if len(command) > 0 && t.isPreviewEnabled() {
-			_, list := t.buildPlusList(command, false)
+			_, list := t.buildPlusList(command, false, false)
 			t.cancelPreview()
 			t.previewBox.Set(reqPreviewEnqueue, previewRequest{command, t.pwindow, t.evaluateScrollOffset(), list})
 		}
@@ -2649,7 +2652,7 @@ func (t *Terminal) Loop() {
 				if t.hasPreviewer() {
 					togglePreview(!t.previewer.enabled)
 					if t.previewer.enabled {
-						valid, list := t.buildPlusList(t.previewOpts.command, false)
+						valid, list := t.buildPlusList(t.previewOpts.command, false, false)
 						if valid {
 							t.cancelPreview()
 							t.previewBox.Set(reqPreviewEnqueue,
@@ -2664,6 +2667,10 @@ func (t *Terminal) Loop() {
 					t.previewed.version = 0
 					req(reqPreviewRefresh)
 				}
+			case actTransformPrompt:
+				prompt := t.executeCommand(a.a, false, true, true)
+				t.prompt, t.promptLen = t.parsePrompt(prompt)
+				req(reqPrompt)
 			case actTransformQuery:
 				query := t.executeCommand(a.a, false, true, true)
 				t.input = []rune(query)
@@ -3036,7 +3043,7 @@ func (t *Terminal) Loop() {
 			case actReload, actReloadSync:
 				t.failed = nil
 
-				valid, list := t.buildPlusList(a.a, false)
+				valid, list := t.buildPlusList(a.a, false, false)
 				if !valid {
 					// We run the command even when there's no match
 					// 1. If the template doesn't have any slots

test/test_go.rb

@@ -1806,6 +1806,15 @@ class TestGoFZF < TestBase
     tmux.until { |lines| assert_equal '> RAB', lines[-1] }
   end
 
+  def test_transform_prompt
+    tmux.send_keys %{#{FZF} --bind 'ctrl-r:transform-query(rev <<< {q}),ctrl-u:transform-query: tr "[:lower:]" "[:upper:]" <<< {q}' --query bar}, :Enter
+    tmux.until { |lines| assert_equal '> bar', lines[-1] }
+    tmux.send_keys 'C-r'
+    tmux.until { |lines| assert_equal '> rab', lines[-1] }
+    tmux.send_keys 'C-u'
+    tmux.until { |lines| assert_equal '> RAB', lines[-1] }
+  end
+
   def test_clear_selection
     tmux.send_keys %(seq 100 | #{FZF} --multi --bind space:clear-selection), :Enter
     tmux.until { |lines| assert_equal 100, lines.match_count }