transform-(with-)nth: use whole output, no cycling

- Rotation of '|'-separated values applied to transform and
  bg-transform variants, where a.a is the command template
- Output '1|2' turned the binding into '2|1', run as a shell
  command on the next key press
- Output was also cut at '|', breaking --with-nth templates
  like '{2}|{1}'
- Split and rotate only for change-nth and change-with-nth

CHANGELOG.md

@@ -5,6 +5,10 @@ CHANGELOG
 ------
 - Fixed `--with-shell` on Windows not detecting cmd, PowerShell, and pwsh, which made fzf quote commands and entries for a POSIX shell (#4936) (@vimkim)
     - e.g. With `--with-shell "cmd.exe /d /c"`, `--preview '"C:\Program Files\nu\bin\nu.exe" --version'` failed
+- `transform-nth` and `transform-with-nth` (and their `bg-` variants) no longer split the output at `|`
+    - Only `change-nth` and `change-with-nth` rotate through `|`-separated values
+    - Fixed the bound command being replaced with the output. e.g. With `transform-nth(echo '1|2')`, the next key press ran `2|1` as a shell command.
+    - A `--with-nth` template in the output can now contain `|`. e.g. `{2}|{1}` was cut to `{2}`.
 - nushell
     - The completion integration now requires nushell 0.116.1 or above, where an interactive completer can take the terminal through the `@interactive` attribute (#4934) (@sim590)
 

man/man1/fzf.1

@@ -2166,8 +2166,8 @@ A key or an event can be bound to one or more of the following actions.
     \fBtransform\-header\-label(...)\fR  (transform header label using an external command)
     \fBtransform\-input\-label(...)\fR   (transform input label using an external command)
     \fBtransform\-list\-label(...)\fR    (transform list label using an external command)
-    \fBtransform\-nth(...)\fR           (transform nth using an external command)
-    \fBtransform\-with\-nth(...)\fR      (transform with-nth using an external command)
+    \fBtransform\-nth(...)\fR           (transform nth using an external command; no rotation, output is used as a whole)
+    \fBtransform\-with\-nth(...)\fR      (transform with-nth using an external command; no rotation, output is used as a whole)
     \fBtransform\-pointer(...)\fR       (transform pointer using an external command)
     \fBtransform\-preview\-label(...)\fR (transform preview label using an external command)
     \fBtransform\-prompt(...)\fR        (transform prompt string using an external command)

src/terminal.go

@@ -7304,8 +7304,11 @@ func (t *Terminal) Loop() error {
 				req(reqList, reqInfo)
 			case actChangeNth, actTransformNth, actBgTransformNth:
 				capture(true, func(expr string) {
-					// Split nth expression
-					tokens := strings.Split(expr, "|")
+					// Only change-nth cycles through '|'-separated values
+					tokens := []string{expr}
+					if a.t == actChangeNth {
+						tokens = strings.Split(expr, "|")
+					}
 					if nth, err := splitNth(tokens[0]); err == nil || len(expr) == 0 {
 						// Changed
 						newNth = &nth
@@ -7328,7 +7331,10 @@ func (t *Terminal) Loop() error {
 					break Action
 				}
 				capture(true, func(expr string) {
-					tokens := strings.Split(expr, "|")
+					tokens := []string{expr}
+					if a.t == actChangeWithNth {
+						tokens = strings.Split(expr, "|")
+					}
 					withNthExpr := tokens[0]
 					if len(tokens) > 1 {
 						a.a = strings.Join(append(tokens[1:], tokens[0]), "|")

test/test_core.rb

@@ -2374,6 +2374,25 @@ class TestCore < TestInteractive
     tmux.until { |lines| assert lines.any_include?('a b c') || lines.any_include?('d e f') }
   end
 
+  def test_transform_nth_output_does_not_replace_command
+    # '|' in the output must not be treated as a list to cycle through
+    File.write(tempname, '')
+    tmux.send_keys %(echo 'a b' | #{FZF} --with-nth .. --bind "space:transform-nth(echo >> #{tempname}; echo '1|2')+transform-with-nth(echo >> #{tempname}; echo '1|2')"), :Enter
+    tmux.until { |lines| assert_equal 1, lines.item_count }
+    3.times do |i|
+      tmux.send_keys :Space
+      wait { assert_equal 2 * (i + 1), File.readlines(tempname).length }
+    end
+  end
+
+  def test_transform_with_nth_output_with_pipe
+    File.write(tempname, '{2}|{1}')
+    tmux.send_keys %(echo 'a b' | #{FZF} --with-nth .. --bind 'space:transform-with-nth(cat #{tempname})'), :Enter
+    tmux.until { |lines| assert lines.any_include?('a b') }
+    tmux.send_keys :Space
+    tmux.until { |lines| assert lines.any_include?('b|a') }
+  end
+
   # Regression: actions emitted by bg-transform must affect the iteration that
   # processes the async result, not the (no-longer-active) iteration that
   # scheduled the transform. Covers reload (newCommand) and exclude (denylist).