Add transform-query(...) action

Test case authored by @SpicyLemon

Close #1930
Close #2465
Close #2559
Close #2509 (e.g. fzf --bind 'space:transform-query:printf %s%s {q} {}')

5 files changed, 51 insertions, 7 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0ae8edaa..3608f4e9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,7 +31,23 @@ CHANGELOG
   # Both actions respect --layout option
   seq 10 | fzf --multi --bind ctrl-n:next-selected,ctrl-p:prev-selected --layout reverse
   ```
-- Added `change-query(...)` action
+- Added `change-query(...)` action that simply changes the query string to the
+  given static string. This can be useful when used with `--listen`.
+  ```sh
+  curl localhost:6266 -d "change-query:$(date)"
+  ```
+- Added `transform-query(...)` action for transforming the query string using
+  an external command
+  ```sh
+  # Press space to convert the query to uppercase letters
+  fzf --bind 'space:transform-query(tr [:lower:] [:upper:] <<< {q})'
+
+  # Bind it to 'change' event for automatic conversion
+  fzf --bind 'change:transform-query(tr [:lower:] [:upper:] <<< {q})'
+
+  # Can only type numbers
+  fzf --bind 'change:transform-query(sed 's/[^0-9]//g' <<< {q})'
+  ```
 - `put` action can optionally take an argument string
   ```sh
   # a will put 'alpha' on the prompt, ctrl-b will put 'bravo'
diff --git a/man/man1/fzf.1 b/man/man1/fzf.1
index b6488bdb..f5e01b6e 100644
--- a/man/man1/fzf.1
+++ b/man/man1/fzf.1
@@ -1023,6 +1023,7 @@ 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-query(...)\fR       (transform query string using an external command)
     \fBunbind(...)\fR                (unbind bindings)
     \fBunix-line-discard\fR          \fIctrl-u\fR
     \fBunix-word-rubout\fR           \fIctrl-w\fR
diff --git a/src/options.go b/src/options.go
index f25b6e73..1288fbe4 100644
--- a/src/options.go
+++ b/src/options.go
@@ -890,7 +890,7 @@ const (
 
 func init() {
 	executeRegexp = regexp.MustCompile(
-		`(?si)[:+](execute(?:-multi|-silent)?|reload|preview|change-query|change-prompt|change-preview-window|change-preview|(?:re|un)bind|pos|put)`)
+		`(?si)[:+](execute(?:-multi|-silent)?|reload|preview|change-query|change-prompt|change-preview-window|change-preview|(?:re|un)bind|pos|put|transform-query)`)
 	splitRegexp = regexp.MustCompile("[,:]+")
 	actionNameRegexp = regexp.MustCompile("(?i)^[a-z-]+")
 }
@@ -1207,6 +1207,8 @@ func isExecuteAction(str string) actionType {
 		return actExecuteMulti
 	case "put":
 		return actPut
+	case "transform-query":
+		return actTransformQuery
 	}
 	return actIgnore
 }
diff --git a/src/terminal.go b/src/terminal.go
index 68a099cf..2d18f791 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -308,6 +308,7 @@ const (
 	actToggleSort
 	actTogglePreview
 	actTogglePreviewWrap
+	actTransformQuery
 	actPreview
 	actChangePreview
 	actChangePreviewWindow
@@ -2014,10 +2015,11 @@ func (t *Terminal) redraw(clear bool) {
 	t.printAll()
 }
 
-func (t *Terminal) executeCommand(template string, forcePlus bool, background bool) {
+func (t *Terminal) executeCommand(template string, forcePlus bool, background bool, captureFirstLine bool) string {
+	line := ""
 	valid, list := t.buildPlusList(template, forcePlus)
 	if !valid {
-		return
+		return line
 	}
 	command := t.replacePlaceholder(template, forcePlus, string(t.input), list)
 	cmd := util.ExecCommand(command, false)
@@ -2033,11 +2035,21 @@ func (t *Terminal) executeCommand(template string, forcePlus bool, background bo
 		t.refresh()
 	} else {
 		t.tui.Pause(false)
-		cmd.Run()
+		if captureFirstLine {
+			out, _ := cmd.StdoutPipe()
+			reader := bufio.NewReader(out)
+			cmd.Start()
+			line, _ = reader.ReadString('\n')
+			line = strings.TrimRight(line, "\r\n")
+			cmd.Wait()
+		} else {
+			cmd.Run()
+		}
 		t.tui.Resume(false, false)
 	}
 	t.executing.Set(false)
 	cleanTemporaryFiles()
+	return line
 }
 
 func (t *Terminal) hasPreviewer() bool {
@@ -2610,9 +2622,9 @@ func (t *Terminal) Loop() {
 			switch a.t {
 			case actIgnore:
 			case actExecute, actExecuteSilent:
-				t.executeCommand(a.a, false, a.t == actExecuteSilent)
+				t.executeCommand(a.a, false, a.t == actExecuteSilent, false)
 			case actExecuteMulti:
-				t.executeCommand(a.a, true, false)
+				t.executeCommand(a.a, true, false, false)
 			case actInvalid:
 				t.mutex.Unlock()
 				return false
@@ -2635,6 +2647,10 @@ func (t *Terminal) Loop() {
 					t.previewed.version = 0
 					req(reqPreviewRefresh)
 				}
+			case actTransformQuery:
+				query := t.executeCommand(a.a, false, true, true)
+				t.input = []rune(query)
+				t.cx = len(t.input)
 			case actToggleSort:
 				t.sort = !t.sort
 				changed = true
diff --git a/test/test_go.rb b/test/test_go.rb
index 4b2856eb..a4d2e2a8 100755
--- a/test/test_go.rb
+++ b/test/test_go.rb
@@ -1797,6 +1797,15 @@ class TestGoFZF < TestBase
     tmux.until { |lines| assert_equal '> foobarbaz', lines.last }
   end
 
+  def test_transform_query
+    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 }