unmap: fail if the mapping is currently executing

When unmapping a key sequence that is currently executing, we continue
executing freed memory which can have weird effects.  Let's instead
throw an error if that happens. In future we can support unmap in
this scenario.

Closes #4896

src/commands.cc

@@ -1933,10 +1933,15 @@ const CommandDesc unmap_key_cmd = {
         if (key.size() != 1)
             throw runtime_error("only a single key can be unmapped");
 
-        if (keymaps.is_mapped(key[0], keymap_mode) and
-            (parser.positional_count() < 4 or
-             (keymaps.get_mapping(key[0], keymap_mode).keys ==
-              parse_keys(parser[3]))))
+        if (not keymaps.is_mapped(key[0], keymap_mode))
+            return;
+        auto& mapping = keymaps.get_mapping(key[0], keymap_mode);
+
+        if (mapping.is_executing)
+            throw runtime_error("cannot unmap key that is currently executing");
+
+        if (parser.positional_count() < 4 or
+             (mapping.keys == parse_keys(parser[3])))
             keymaps.unmap_key(key[0], keymap_mode);
     }
 };
@@ -2653,8 +2658,12 @@ void enter_user_mode(Context& context, String mode_name, KeymapMode mode, bool l
         InputHandler::ScopedForceNormal force_normal{context.input_handler(), {}};
 
         ScopedEdition edition(context);
+
+        {
+            ScopedSetBool executing_mapping{mapping.is_executing};
             for (auto& key : mapping.keys)
                 context.input_handler().handle_key(key);
+        }
 
         if (lock)
             enter_user_mode(context, std::move(mode_name), mode, true);

src/input_handler.cc

@@ -1773,7 +1773,10 @@ void InputHandler::handle_key(Key key)
     if (keymaps.is_mapped(key, keymap_mode) and not m_context.keymaps_disabled())
     {
         ScopedSetBool disable_history{context().history_disabled()};
-        for (auto& k : keymaps.get_mapping(key, keymap_mode).keys)
+
+        auto& mapping = keymaps.get_mapping(key, keymap_mode);
+        ScopedSetBool executing_mapping{mapping.is_executing};
+        for (auto& k : mapping.keys)
             process_key(k);
     }
     else

src/keymap_manager.cc

@@ -40,8 +40,8 @@ bool KeymapManager::is_mapped(Key key, KeymapMode mode) const
            (m_parent and m_parent->is_mapped(key, mode));
 }
 
-const KeymapManager::KeymapInfo&
-KeymapManager::get_mapping(Key key, KeymapMode mode) const
+KeymapManager::KeymapInfo&
+KeymapManager::get_mapping(Key key, KeymapMode mode)
 {
     auto it = m_mapping.find(KeyAndMode{key, mode});
     if (it != m_mapping.end())

src/keymap_manager.hh

@@ -6,6 +6,7 @@
 #include "hash.hh"
 #include "string.hh"
 #include "hash_map.hh"
+#include "utils.hh"
 #include "vector.hh"
 
 namespace Kakoune
@@ -42,8 +43,9 @@ public:
     {
         KeyList keys;
         String docstring;
+        NestedBool is_executing{};
     };
-    const KeymapInfo& get_mapping(Key key, KeymapMode mode) const;
+    KeymapInfo& get_mapping(Key key, KeymapMode mode);
 
     using UserModeList = Vector<String>;
     UserModeList& user_modes() {

src/normal.cc

@@ -2033,6 +2033,7 @@ void exec_user_mappings(Context& context, NormalParams params)
 
         ScopedEdition edition(context);
         ScopedSelectionEdition selection_edition{context};
+        ScopedSetBool executing_mapping{mapping.is_executing};
         for (auto& key : mapping.keys)
             context.input_handler().handle_key(key);
     }, "user mapping",

test/regression/4896-unmap-executing-mapping/cmd

@@ -0,0 +1 @@
+<space>u

test/regression/4896-unmap-executing-mapping/in

@@ -0,0 +1 @@
+

test/regression/4896-unmap-executing-mapping/out

@@ -0,0 +1 @@
+123

test/regression/4896-unmap-executing-mapping/rc

@@ -0,0 +1 @@
+map global user u %{i123<esc>:unmap global user u<ret>i456<esc>}