clipboard kitten: Dont set clipboard when getting clipboard

The previous behavior meant getting the clipboard would
first empty it if STDIN was null or empty which can easily happen when
run non-interactively.

Fixes #6302

docs/changelog.rst

@@ -48,6 +48,8 @@ Detailed list of changes
 
 - clipboard kitten: Fix a bug causing the last MIME type available on the clipboard not being recognized when pasting
 
+- clipboard kitten: Dont set clipboard when getting clipboard in filter mode (:iss:`6302`)
+
 - Fix regression in 0.28.0 causing color fringing when rendering in transparent windows on light backgrounds (:iss:`6209`)
 
 - show_key kitten: In kitty mode show the actual bytes sent by the terminal rather than a re-encoding of the parsed key event

kittens/clipboard/legacy.go

@@ -99,7 +99,9 @@ func run_plain_text_loop(opts *Options) (err error) {
 	stdin_is_tty := tty.IsTerminal(os.Stdin.Fd())
 	var data_src io.Reader
 	var tempfile *os.File
-	if !stdin_is_tty {
+	if !stdin_is_tty && !opts.GetClipboard {
+		// we dont read STDIN when getting clipboard as it makes it hard to use the kitten in contexts where
+		// the user does not control STDIN such as being execed from other programs.
 		data_src, tempfile, err = preread_stdin()
 		if err != nil {
 			return err

kittens/clipboard/main.py

@@ -50,7 +50,7 @@ Read or write to the system clipboard.
 
 This kitten operates most simply in :italic:`filter mode`.
 To set the clipboard text, pipe in the new text on :file:`STDIN`. Use the
-:option:`--get-clipboard` option to output the current clipboard text content to
+:option:`--get-clipboard` option to instead output the current clipboard text content to
 :file:`STDOUT`. Note that copying from the clipboard will cause a permission
 popup, see :opt:`clipboard_control` for details.