Actually fully disable system clipboard (xonsh#5155) (xonsh#5261)

Allow to fully disable system clipboard

Fixes xonsh#5155

In VI mode, disabling "delete" hotkeys isn't enough.

After discussion in xonsh#5261, we don't change the default behavior but
allow fully disabling the system clipboard to better support the
use-case of VI mode user.

Co-authored-by: Nathan Monfils <nmo@escaux.com>

news/disable-system-clipboard.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* System clipboard can be fully disabled using ``$XONSH_USE_SYSTEM_CLIPBOARD``.
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

xonsh/environ.py

@@ -1689,7 +1689,14 @@ class PTKSetting(PromptSetting):  # sub-classing -> sub-group
     )
     XONSH_COPY_ON_DELETE = Var.with_default(
         False,
-        "Whether to copy words/lines to clipboard on deletion (must be set in .xonshrc file)."
+        "Whether to copy words/lines to clipboard on deletion (must be set in the run control file)."
+        "Does not have any effect in ``vi_mode``."
+        "Only available under the prompt-toolkit shell.",
+    )
+    XONSH_USE_SYSTEM_CLIPBOARD = Var.with_default(
+        True,
+        "Whether to let the shell use the system clipboard (must be set in the run control file)."
+        "The main use-case is to fully disable clipboard integration in ``vi_mode``."
         "Only available under the prompt-toolkit shell.",
     )
     XONSH_CTRL_BKSP_DELETION = Var.with_default(

xonsh/ptk_shell/shell.py

@@ -7,6 +7,7 @@
 
 from prompt_toolkit import ANSI
 from prompt_toolkit.auto_suggest import AutoSuggestFromHistory
+from prompt_toolkit.clipboard import InMemoryClipboard
 from prompt_toolkit.enums import EditingMode
 from prompt_toolkit.formatted_text import PygmentsTokens, to_formatted_text
 from prompt_toolkit.history import ThreadedHistory
@@ -193,8 +194,11 @@ def __init__(self, **kwargs):
         ptk_args.setdefault("history", self.history)
         if not XSH.env.get("XONSH_COPY_ON_DELETE", False):
             disable_copy_on_deletion()
-        if HAVE_SYS_CLIPBOARD:
-            ptk_args.setdefault("clipboard", PyperclipClipboard())
+        if HAVE_SYS_CLIPBOARD and (XSH.env.get("XONSH_USE_SYSTEM_CLIPBOARD", True)):
+            default_clipboard = PyperclipClipboard()
+        else:
+            default_clipboard = InMemoryClipboard()
+        ptk_args.setdefault("clipboard", default_clipboard)
         self.prompter: PromptSession = PromptSession(**ptk_args)
 
         self.prompt_formatter = PTKPromptFormatter(self)