Clear the control-C cancel flag earlier, allowing event handlers to run

When the user presses control-C, fish marks a cancellation signal which
prevents fish script from running, allowing it to properly unwind.
Prior to this commit, the signal was cleared in the reader. However this
missed the case where a binding would set $fish_bind_mode which would
trigger event handlers: the event handlers would be skipped because of
the cancellation flag was still set. This is similar to #6937.

Let's clear the flag earlier, as soon as we it's set, in inputter_t.
Fixes #8125.

CHANGELOG.rst

@@ -13,6 +13,7 @@ Scripting improvements
 
 Interactive improvements
 ------------------------
+Vi mode cursors are now set properly after control-C. (:issue:`8125`).
 
 New or improved bindings
 ^^^^^^^^^^^^^^^^^^^^^^^^

src/input.cpp

@@ -329,6 +329,10 @@ void inputter_t::prepare_to_select() /* override */ {
 }
 
 void inputter_t::select_interrupted() /* override */ {
+    // Readline commands may be bound to \cc which also sets the cancel flag.
+    // See #6937, #8125.
+    signal_clear_cancel();
+
     // Fire any pending events and reap stray processes, including printing exit status messages.
     auto &parser = *this->parser_;
     event_fire_delayed(parser);

src/reader.cpp

@@ -2943,8 +2943,7 @@ void reader_data_t::handle_readline_command(readline_cmd_t c, readline_loop_stat
                 set_command_line_and_position(&command_line, L"", 0);
                 s_reset_abandoning_line(&screen, termsize_last().width - command_line.size());
 
-                // Post fish_cancel, allowing it to fire.
-                signal_clear_cancel();
+                // Post fish_cancel.
                 event_fire_generic(parser(), L"fish_cancel");
             }
             break;
@@ -3977,10 +3976,6 @@ maybe_t<wcstring> reader_data_t::readline(int nchars_or_0) {
                 history_search.reset();
             }
 
-            // Readline commands may be bound to \cc which also sets the cancel flag.
-            // See #6937.
-            signal_clear_cancel();
-
             rls.last_cmd = readline_cmd;
         } else {
             // Ordinary char.

tests/pexpects/bind_mode_events.py

@@ -1,5 +1,7 @@
 #!/usr/bin/env python3
 from pexpect_helper import SpawnedProc
+import os
+import signal
 
 sp = SpawnedProc()
 send, sendline, sleep, expect_prompt = sp.send, sp.sendline, sp.sleep, sp.expect_prompt
@@ -33,3 +35,21 @@ sleep(0.050)
 
 send("echo mode changes: $MODE_CHANGES\r")
 expect_prompt("\r\nmode changes: default insert default insert\r\n")
+
+# Regression test for #8125.
+# Control-C should return us to insert mode.
+send("set -e MODE_CHANGES\r")
+expect_prompt()
+
+# Put some text on the command line and then go back to normal mode.
+send("echo stuff")
+sp.expect_str("echo stuff")
+send("\033")
+sleep(0.050)
+
+os.kill(sp.spawn.pid, signal.SIGINT)
+sleep(0.050)
+
+# We should be back in insert mode now.
+send("echo mode changes: $MODE_CHANGES\r")
+expect_prompt("\r\nmode changes: default insert\r\n")