Control-C to simply clear commandline buffer again

Commit 5f849d0 changed control-C to print an inverted ^C and then a newline.

The original motivation was

> In bash if you type something and press ctrl-c then the content of the line
> is preserved and the cursor is moved to a new line. In fish the ctrl-c just
> clears the line. For me the behaviour of bash is a bit better, because it
> allows me to type something then press ctrl-c and I have the typed string
> in the log for further reference.

This sounds like a valid use case in some scenarios but I think that most
abandoned commands are noise. After all, the user erased them. Also, now that
we have undo that can be used to get back a limited set of canceled commands.

I believe the original motivation for existing behavior (in other shells) was
that TERM=dumb does not support erasing characters. Similarly, other shells
like to leave behind other artifacts, for example when using tab-completion
or in their interactive menus but we generally don't.

Control-C is the obvious way to quickly clear a multi-line commandline.
IPython does the same. For the other behavior we have Alt-# although that's
probably not very well-known.

Restore the old Control-C behavior of simply clearing the command line.

Our unused __fish_cancel_commandline still prints the ^C. For folks who
have explicitly bound ^C to that, it's probably better to keep the existing
behavior, so let's leave this one.

Previous attempt at #4713 fizzled.

Closes #10213

CHANGELOG.rst

@@ -30,6 +30,7 @@ Scripting improvements
 
 Interactive improvements
 ------------------------
+- :kbd:`Control-C` during command input no longer prints ``^C`` and a new prompt but merely clears the command line. This restores the behavior from version 2.2. To revert to the old behavior use ``bind \cc __fish_cancel_commandline`` (:issue:`10213`).
 - Command-specific tab completions may now offer results whose first character is a period. For example, it is now possible to tab-complete ``git add`` for files with leading periods. The default file completions hide these files, unless the token itself has a leading period (:issue:`3707`).
 - The :kbd:`Control-R` history search now uses glob syntax (:issue:`10131`).
 

src/reader.rs

@@ -72,7 +72,7 @@ use crate::io::IoChain;
 use crate::kill::{kill_add, kill_replace, kill_yank, kill_yank_rotate};
 use crate::libc::MB_CUR_MAX;
 use crate::operation_context::{get_bg_context, OperationContext};
-use crate::output::{parse_color, Outputter};
+use crate::output::Outputter;
 use crate::pager::{PageRendering, Pager, SelectionMotion};
 use crate::parse_constants::SourceRange;
 use crate::parse_constants::{ParseTreeFlags, ParserTestErrorBits};
@@ -2060,35 +2060,10 @@ impl ReaderData {
                 if self.command_line.is_empty() {
                     return;
                 }
-                let outp = Outputter::stdoutput().get_mut();
-                // Move cursor to the end of the line.
-                let end = self.command_line.len();
-                self.update_buff_pos(EditableLineTag::Commandline, Some(end));
-                self.autosuggestion.clear();
-                // Repaint also changes the actual cursor position
-                if self.is_repaint_needed(None) {
-                    self.layout_and_repaint(L!("cancel"));
-                }
-
-                if let Some(fish_color_cancel) = self.vars().get(L!("fish_color_cancel")) {
-                    outp.set_color(
-                        parse_color(&fish_color_cancel, false),
-                        parse_color(&fish_color_cancel, true),
-                    );
-                }
-                outp.write_wstr(L!("^C"));
-                outp.set_color(RgbColor::RESET, RgbColor::RESET);
-
-                // We print a newline last so the prompt_sp hack doesn't get us.
-                outp.push(b'\n');
-
-                self.set_command_line_and_position(
+                self.push_edit(
                     EditableLineTag::Commandline,
-                    L!("").to_owned(),
-                    0,
+                    Edit::new(0..self.command_line.len(), L!("").to_owned()),
                 );
-                self.screen
-                    .reset_abandoning_line(usize::try_from(termsize_last().width).unwrap());
 
                 // Post fish_cancel.
                 event::fire_generic(self.parser(), L!("fish_cancel").to_owned(), vec![]);

tests/pexpects/cancel_event.py

@@ -27,13 +27,16 @@ if "CI" in os.environ:
 send("not executed")
 sleep(timeout)
 os.kill(sp.spawn.pid, signal.SIGINT)
-sp.expect_str("not executed^C")
-expect_prompt(increment=False)
+sendline("echo marker")
+sp.expect_str("marker")
+expect_prompt()
 
 sendline("function cancelhandler --on-event fish_cancel ; echo yay cancelled ; end")
 expect_prompt()
 send("still not executed")
 sleep(timeout)
 os.kill(sp.spawn.pid, signal.SIGINT)
-expect_str("still not executed^C")
-expect_prompt("yay cancelled", increment=False)
+expect_str("yay cancelled")
+sendline("echo marker")
+sp.expect_str("marker")
+expect_prompt()