Switch out of an input method and back with a lone Shift (#14975)

* Switch out of an input method and back with a lone Shift

Fcitx's alternate trigger only acts while an engine like Pinyin is or was
active, so Shift + letter and plain Latin typing are unaffected. It needs
Shift releases intact, which the both-Shifts Caps Lock option prevented.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Follow XDG_CONFIG_HOME in the Shift migration and test it

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

test/shell.d/input-method-checks.py

@@ -66,6 +66,7 @@ class InputMethodTest(unittest.TestCase):
         self.assertEqual(keys["Behavior"]["ActiveByDefault"], "False")
         self.assertNotIn("Control+space", keys["Hotkey/TriggerKeys"].values())
         self.assertEqual(set(keys["Hotkey/TriggerKeys"].values()), {"Zenkaku_Hankaku", "Hangul"})
+        self.assertEqual(keys["Hotkey/AltTriggerKeys"], {"0": "Shift_L"})
 
   def test_vconsole_variants_quotes_and_japanese_without_preference(self):
     self.preference.unlink()

test/shell.d/shift-switch-migration-test.sh

@@ -0,0 +1,75 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/base-test.sh"
+
+migration="$ROOT/migrations/1791676907.sh"
+test_dir=$(mktemp -d)
+trap 'rm -rf "$test_dir"' EXIT
+mkdir -p "$test_dir/bin"
+export CALL_LOG="$test_dir/calls"
+
+# A live Fcitx is asked to reload; never reach the real session bus.
+cat >"$test_dir/bin/busctl" <<'SH'
+#!/bin/bash
+printf 'busctl %s\n' "$*" >>"$CALL_LOG"
+SH
+chmod +x "$test_dir/bin/busctl"
+
+# Runs the migration twice, as a retried update would. The caller's own
+# XDG_CONFIG_HOME would point at the developer's real config, so it is cleared
+# unless a case sets MIGRATION_XDG_CONFIG_HOME.
+migrate() {
+  local home=$1
+  for run in 1 2; do
+    env -u XDG_CONFIG_HOME ${MIGRATION_XDG_CONFIG_HOME:+XDG_CONFIG_HOME="$MIGRATION_XDG_CONFIG_HOME"} \
+      HOME="$home" PATH="$test_dir/bin:$PATH" bash -euo pipefail "$migration" >/dev/null
+  done
+}
+
+fresh_home() {
+  rm -rf "$test_dir/home" "$CALL_LOG"
+  mkdir -p "$test_dir/home/.config/fcitx5"
+  printf '%s' "$1" >"$test_dir/home/.config/fcitx5/config"
+}
+
+fresh_home $'[Hotkey/TriggerKeys]\n0=Hangul\n\n[Hotkey/AltTriggerKeys]\n\n[Behavior]\nActiveByDefault=False\n'
+migrate "$test_dir/home"
+[[ $(<"$test_dir/home/.config/fcitx5/config") == $'[Hotkey/TriggerKeys]\n0=Hangul\n\n[Hotkey/AltTriggerKeys]\n0=Shift_L\n\n[Behavior]\nActiveByDefault=False' ]] ||
+  fail "an empty list gets Shift_L once" "$(<"$test_dir/home/.config/fcitx5/config")"
+[[ $(grep -c ReloadConfig "$CALL_LOG") == 1 ]] || fail "Fcitx reloads only when the list changes" "$(cat "$CALL_LOG")"
+pass "an empty list gets Shift_L once, and Fcitx reloads once"
+
+fresh_home $'[Hotkey/AltTriggerKeys]\n0=Shift_R\n'
+migrate "$test_dir/home"
+[[ $(<"$test_dir/home/.config/fcitx5/config") == $'[Hotkey/AltTriggerKeys]\n0=Shift_R' && ! -e $CALL_LOG ]] ||
+  fail "a chosen key is kept" "$(<"$test_dir/home/.config/fcitx5/config")"
+pass "a list the user filled is kept"
+
+fresh_home $'[Behavior]\nActiveByDefault=False\n'
+migrate "$test_dir/home"
+[[ $(<"$test_dir/home/.config/fcitx5/config") == $'[Behavior]\nActiveByDefault=False' ]] ||
+  fail "a missing list keeps Fcitx's own Shift_L default" "$(<"$test_dir/home/.config/fcitx5/config")"
+rm -rf "$test_dir/home"
+mkdir -p "$test_dir/home"
+migrate "$test_dir/home"
+[[ ! -e $test_dir/home/.config/fcitx5/config ]] || fail "no Fcitx config is created"
+pass "a missing list or config is left to Fcitx's default"
+
+fresh_home ""
+mkdir -p "$test_dir/dotfiles"
+printf '[Hotkey/AltTriggerKeys]\n\n' >"$test_dir/dotfiles/fcitx5-config"
+ln -sf "$test_dir/dotfiles/fcitx5-config" "$test_dir/home/.config/fcitx5/config"
+migrate "$test_dir/home"
+[[ -L $test_dir/home/.config/fcitx5/config && $(grep -c '^0=Shift_L$' "$test_dir/dotfiles/fcitx5-config") == 1 ]] ||
+  fail "a symlinked config stays linked and its target is updated" "$(ls -l "$test_dir/home/.config/fcitx5/config"; cat "$test_dir/dotfiles/fcitx5-config")"
+pass "a symlinked config stays linked and its target is updated"
+
+rm -rf "$test_dir/home" "$test_dir/xdg"
+mkdir -p "$test_dir/home" "$test_dir/xdg/fcitx5"
+printf '[Hotkey/AltTriggerKeys]\n' >"$test_dir/xdg/fcitx5/config"
+MIGRATION_XDG_CONFIG_HOME="$test_dir/xdg" migrate "$test_dir/home"
+[[ $(<"$test_dir/xdg/fcitx5/config") == $'[Hotkey/AltTriggerKeys]\n0=Shift_L' ]] ||
+  fail "XDG_CONFIG_HOME is followed" "$(<"$test_dir/xdg/fcitx5/config")"
+pass "the config under XDG_CONFIG_HOME is the one repaired"