Support deletion in whole_word_jumping xontrib (#4788)

This binds Alt/Control+Delete/Backspace to support deletion matching
the motion bindings in `whole_word_jumping`.

Should work mostly out of the box on terminals that generate `\x7f`
when `backspace` is pressed and `\x08` when `control+backspace` is
pressed.  Tested to work on Microsoft Terminal (WSL2).  For
incompatible terminals, users can set `$XONSH_WHOLE_WORD_CTRL_BKSP
= False` to avoid configuration of the `control+backspace` binding.

news/extend-whole-word-jumping.rst

@@ -0,0 +1,26 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* Extended `whole_word_jumping` xontrib with matching bindings for
+  `delete` and `backspace`. The `XONSH_WHOLE_WORD_CTRL_BKSP` environment
+  variable can be set to `False` to avoid binding `control+backspace` in
+  incompatible terminals.
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

xontrib/whole_word_jumping.py

@@ -1,14 +1,33 @@
-"""Jumping across whole words (non-whitespace) with Ctrl+Left/Right.
+"""Jump/delete across whole (non-whitespace) words with Ctrl+Left/Right/Delete/Backspace.
 
-Alt+Left/Right remains unmodified to jump over smaller word segments.
-Shift+Delete removes the whole word.
+Control+left/right: Jump to previous/next whole word
+Control+backspace: Delete to beginning of whole word
+Control+delete: Delete to end of whole word
+Shift+delete: Delete whole word
+
+Alt+Left/Right/Delete/Backspace remain unmodified:
+
+Alt+left/right: Jump to previous/next token
+Alt+backspace: Delete to beginning of token
+Alt+delete: Delete to end of token
+
+Some terminals cannot differentiate between Backspace and Control+Backspace.
+In this case, users can set `$XONSH_WHOLE_WORD_CTRL_BKSP = False` to skip
+configuration of the Control+Backspace key binding.
 """
+
+import prompt_toolkit.input.ansi_escape_sequences as ansiseq
+import prompt_toolkit.input.win32 as ptk_win32
+from prompt_toolkit.filters import EmacsInsertMode, ViInsertMode
+from prompt_toolkit.key_binding.bindings.named_commands import get_by_name
 from prompt_toolkit.keys import Keys
 
-from xonsh.built_ins import XonshSession
+from xonsh.built_ins import XSH, XonshSession
+from xonsh.platform import ON_WINDOWS
 
 
 def custom_keybindings(bindings, **kw):
+    insert_mode = ViInsertMode() | EmacsInsertMode()
 
     # Key bindings for jumping over whole words (everything that's not
     # white space) using Ctrl+Left and Ctrl+Right;
@@ -29,8 +48,8 @@ def custom_keybindings(bindings, **kw):
         if pos:
             buff.cursor_position += pos
 
-    @bindings.add(Keys.ShiftDelete)
-    def shift_delete(event):
+    @bindings.add(Keys.ShiftDelete, filter=insert_mode)
+    def delete_surrounding_big_word(event):
         buff = event.current_buffer
         startpos, endpos = buff.document.find_boundaries_of_current_word(WORD=True)
         startpos = buff.cursor_position + startpos - 1
@@ -40,6 +59,39 @@ def custom_keybindings(bindings, **kw):
         buff.text = buff.text[:startpos] + buff.text[endpos:]
         buff.cursor_position = startpos
 
+    @bindings.add(Keys.ControlDelete, filter=insert_mode)
+    def delete_big_word(event):
+        buff = event.current_buffer
+        pos = buff.document.find_next_word_ending(count=event.arg, WORD=True)
+        if pos:
+            buff.delete(count=pos)
+
+    @bindings.add(Keys.Escape, Keys.Delete, filter=insert_mode)
+    def delete_small_word(event):
+        get_by_name("kill-word").call(event)
+
+    # PTK sets both "\x7f" (^?) and "\x08" (^H) to the same behavior. Refs:
+    # https://github.com/prompt-toolkit/python-prompt-toolkit/blob/65c3d0607c69c19d80abb052a18569a2546280e5/src/prompt_toolkit/input/ansi_escape_sequences.py#L65
+    # https://github.com/prompt-toolkit/python-prompt-toolkit/issues/257#issuecomment-190328366
+    # We patch the ANSI sequences used by PTK.  This requires a terminal
+    # that sends different codes for <backspace> and <control-h>.
+    # PTK sets Keys.Backspace = Keys.ControlH, so we hardcode the code.
+    # Windows has the codes reversed, see https://github.com/xonsh/xonsh/commit/406d20f78f18af39d9bbaf9580b0a763df78a0db
+    if XSH.env.get("XONSH_WHOLE_WORD_CTRL_BKSP", True):
+        CONTROL_BKSP = "\x08"
+        if ON_WINDOWS:
+            # On windows BKSP is "\x08" and CTRL-BKSP is "\x7f"
+            CONTROL_BKSP = "\x7f"
+            ptk_win32.ConsoleInputReader.mappings[b"\x7f"] = CONTROL_BKSP
+        ansiseq.ANSI_SEQUENCES[CONTROL_BKSP] = CONTROL_BKSP
+        ansiseq.REVERSE_ANSI_SEQUENCES[CONTROL_BKSP] = CONTROL_BKSP
+
+        @bindings.add(CONTROL_BKSP, filter=insert_mode)
+        def backward_delete_big_word(event):
+            get_by_name("unix-word-rubout").call(event)
+
+    # backward_delete_small_word works on Alt+Backspace by default
+
 
 def _load_xontrib_(xsh: XonshSession, **_):
     xsh.builtins.events.on_ptk_create(custom_keybindings)