fix(zsh): probe the bound keymap for a -M bindmap's previous binding

.zinit-tmp-subst-bindkey records the widget a key carried before the plugin bound it, so
unload can put it back. That probe always read the `main' keymap, even when the intercepted
bind itself carried `-M <keymap>'. Unloading a plugin whose bindmap'' remapped a key bound
with -M therefore restored main's widget into the other keymap, silently replacing whatever
had been bound there.

Pass the same -M <keymap> to the probing `bindkey' whenever opts[-M] is set.

The existing -M case only asserted that a remap does not leak out of `emacs', and it assumed
`main' was linked to `viins' in the test shell -- `main' is `emacs' unless EDITOR/VISUAL is
vi-flavored, so the leak it was meant to catch was invisible. Link `main' to `viins'
explicitly and add a case that pre-binds the remapped key to different widgets in `emacs' and
`main', which makes restoring the wrong keymap's widget detectable.

Signed-off-by: Vladislav Doster <mvdoster@gmail.com>

tests/bindmap.zunit

@@ -126,27 +126,52 @@
 }
 
 @test 'bindmap confines a -M remap to that keymap' {
-  # `main' is linked to `viins' in the test shell, so `emacs' is used to tell
-  # the keymaps apart.
+  # `main' defaults to `emacs' unless EDITOR/VISUAL is vi-flavored; pin it to `viins' so a remap
+  # that leaked out of `emacs' (a dropped -M) is actually observable in `main'.
   unsetopt ERR_EXIT
+  bindkey -A viins main
   bindmap_fixture bm-keymap
-  function zunit-bm-keymap() { }
+  function zunit-bm-keymap() { ; }
   zle -N zunit-bm-keymap
 
-  zinit as"null" id-as"test/bm-keymap" bindmap'^A -> "^Y"' \
-      atload'!bindkey -M emacs "^A" zunit-bm-keymap' for test/bm-keymap
+  zinit for \
+    as"null" \
+    atload'!bindkey -M emacs "^A" zunit-bm-keymap' \
+    bindmap'^A -> "^Y"' \
+    id-as"test/bm-keymap" \
+  @test/bm-keymap
 
   local -a in_emacs=( ${(f)"$(bindings_for zunit-bm-keymap emacs)"} )
   local -a in_main=( ${(f)"$(bindings_for zunit-bm-keymap)"} )
-  assert $#in_emacs equals 1
+  assert ${#in_emacs} equals 1
   assert "${in_emacs[1]}" contains '"^Y"'
-  assert $#in_main equals 0
+  assert ${#in_main} equals 0
 
   zinit unload -q test/bm-keymap
   in_emacs=( ${(f)"$(bindings_for zunit-bm-keymap emacs)"} )
   assert $#in_emacs equals 0
 }
 
+@test 'bindmap -M restores the keymap-specific previous binding' {
+  # Regression: the previous-binding probe read `main' even for a `-M <map>' bind, so unload
+  # restored the wrong keymap's widget. The remapped key is pre-bound differently in `emacs' and
+  # `main' so restoring the wrong one is detectable.
+  unsetopt ERR_EXIT
+  bindkey -A viins main
+  bindmap_fixture bm-keymap-prev
+  function zunit-bm-keymap-prev() { }
+  zle -N zunit-bm-keymap-prev
+  bindkey -M emacs '^Y' clear-screen    # emacs prior -- must be restored on unload
+  bindkey '^Y' self-insert              # different main prior -- must NOT be what's restored
+
+  zinit as"null" id-as"test/bm-keymap-prev" bindmap'^A -> "^Y"' \
+      atload'!bindkey -M emacs "^A" zunit-bm-keymap-prev' for test/bm-keymap-prev
+  assert "$(bindkey -M emacs '^Y')" contains 'zunit-bm-keymap-prev'
+
+  zinit unload -q test/bm-keymap-prev
+  assert "$(bindkey -M emacs '^Y')" contains 'clear-screen'
+}
+
 @test 'bindmap ! form remaps the widget, not the key' {
   unsetopt ERR_EXIT
   bindmap_fixture bm-bang

zinit.zsh

@@ -547,7 +547,10 @@ builtin setopt noaliases
         [[ $bmap_val = hold ]] && return 0
 
         # Quoted - the key sequence may contain spaces, e.g. bindmap'^X -> "^ "'.
-        local prev="${(q)${(s: :)$(builtin bindkey "${(Q)string}")}[-1]#undefined-key}"
+        # Probe the same keymap the bind targets, so unload restores the right prior widget.
+        local -a Mprobe
+        (( ${+opts[-M]} )) && Mprobe=( -M "${opts[-M]}" )
+        local prev="${(q)${(s: :)$(builtin bindkey "${Mprobe[@]}" "${(Q)string}")}[-1]#undefined-key}"
 
         # "-M map" given?
         if (( ${+opts[-M]} )); then