Introduce "local" scope in evaluate-commands

When using `eval` a new scope named 'local' gets pushed for the
whole evaluation, this makes it possible to temporarily set
an option/hook/alias...

Local scopes nest so nested evals do work as expected.

Remove the now trivial with-option command

doc/pages/execeval.asciidoc

@@ -64,3 +64,8 @@ are then restored when the keys have been executed: */*, *"*, *|*, *^*,
 *-with-hooks*::
     Execute keys and trigger existing hooks.
     (See <<hooks#,`:doc hooks`>>)
+
+== Local scope in *evaluate-commands*
+
+When using *evaluate-commands* a new scope, named `local` is inserted.
+See <<scopes#,`:doc scopes`>>

doc/pages/scopes.asciidoc

@@ -36,15 +36,25 @@ Scopes are named as follows:
 *global*::
     global context linked to the instance of Kakoune
 
+*local*::
+    A local scope is inserted by each *evaluate-commands* invocations
+    for its duration. Nested *evaluate-commands* each inject a new
+    local scope whose parent is the previous local scope.
+
+    A local scope is intended for temporarily overwriting some scoped
+    value, such as an option or an alias.
+
+
 The following order of priority applies to the above scopes:
 
---------------------------
-window ]> buffer ]> global
---------------------------
+-----------------------------------
+local ]> window ]> buffer ]> global
+-----------------------------------
 
-The above priority line implies that objects can have individual values that
-will be resolved first in the *window* scope (highest priority), then in
-the *buffer* scope, and finally in the *global* scope (lowest priority).
+The above priority line implies that objects can have individual values
+that will be resolved first in the *local* scope (if it exists), then the
+*window* scope, then in the *buffer* scope, and finally in the *global*
+scope.
 
 Normally, the *buffer* scope keyword means the scope associated with the
 currently active buffer, but it's possible to specify any existing buffer by

rc/windowing/detection.kak

@@ -48,7 +48,7 @@ define-command terminal -params 1.. -docstring %{
     Example usage:
 
         terminal sh
-        with-option windowing_placement horizontal terminal sh
+        evaluate-commands %{ set local windowing_placement horizontal; terminal sh }
 
     See also the 'new' command.
 } %{
@@ -56,29 +56,6 @@ define-command terminal -params 1.. -docstring %{
 }
 complete-command terminal shell
 
-# TODO Move this?
-define-command with-option -params 3.. -docstring %{
-    with-option <option_name> <new_value> <command> [<arguments>]: evaluate a command with a modified option
-} %{
-    evaluate-commands -save-regs s %{
-        evaluate-commands set-register s %exp{%%opt{%arg{1}}}
-        set-option current %arg{1} %arg{2}
-        try %{
-            evaluate-commands %sh{
-                shift 2
-                for arg
-                do
-                    printf "'%s' " "$(printf %s "$arg" | sed "s/'/''/g")"
-                done
-            }
-        } catch %{
-            set-option current %arg{1} %reg{s}
-            fail "with-option: %val{error}"
-        }
-        set-option current %arg{1} %reg{s}
-    }
-}
-
 hook -group windowing global KakBegin .* %{
     evaluate-commands %sh{
         set -- ${kak_opt_windowing_modules}

src/alias_registry.hh

@@ -12,6 +12,9 @@ class AliasRegistry : public SafeCountable
 {
 public:
     AliasRegistry(AliasRegistry& parent) : SafeCountable{}, m_parent(&parent) {}
+
+    void reparent(AliasRegistry& parent) { m_parent = &parent; }
+
     void add_alias(String alias, String command);
     void remove_alias(StringView alias);
     StringView operator[](StringView alias) const;

src/commands.cc

@@ -48,6 +48,24 @@ namespace Kakoune
 
 extern const char* version;
 
+struct LocalScope : Scope
+{
+    LocalScope(Context& context)
+        : Scope(context.scope()), m_context{context}
+    {
+        m_context.m_local_scopes.push_back(this);
+    }
+
+    ~LocalScope()
+    {
+        kak_assert(not m_context.m_local_scopes.empty() and m_context.m_local_scopes.back() == this);
+        m_context.m_local_scopes.pop_back();
+    }
+
+private:
+    Context& m_context;
+};
+
 namespace
 {
 
@@ -215,21 +233,21 @@ const ParameterDesc double_params{ {}, ParameterDesc::Flags::None, 2, 2 };
 static Completions complete_scope(const Context&, CompletionFlags,
                                   StringView prefix, ByteCount cursor_pos)
 {
-   static constexpr StringView scopes[] = { "global", "buffer", "window", };
+   static constexpr StringView scopes[] = { "global", "buffer", "window", "local"};
    return { 0_byte, cursor_pos, complete(prefix, cursor_pos, scopes) };
 }
 
 static Completions complete_scope_including_current(const Context&, CompletionFlags,
                                   StringView prefix, ByteCount cursor_pos)
 {
-   static constexpr StringView scopes[] = { "global", "buffer", "window", "current" };
+   static constexpr StringView scopes[] = { "global", "buffer", "window", "local", "current" };
    return { 0_byte, cursor_pos, complete(prefix, cursor_pos, scopes) };
 }
 
 static Completions complete_scope_no_global(const Context&, CompletionFlags,
                                             StringView prefix, ByteCount cursor_pos)
 {
-   static constexpr StringView scopes[] = { "buffer", "window", "current" };
+   static constexpr StringView scopes[] = { "buffer", "window", "local", "current" };
    return { 0_byte, cursor_pos, complete(prefix, cursor_pos, scopes) };
 }
 
@@ -395,6 +413,8 @@ Scope* get_scope_ifp(StringView scope, const Context& context)
         return &context.buffer();
     else if (prefix_match("window", scope))
         return &context.window();
+    else if (prefix_match("local", scope))
+        return context.local_scope();
     else if (prefix_match(scope, "buffer="))
         return &BufferManager::instance().get_buffer(scope.substr(7_byte));
     return nullptr;
@@ -2168,6 +2188,7 @@ const CommandDesc execute_keys_cmd = {
     }
 };
 
+
 const CommandDesc evaluate_commands_cmd = {
     "evaluate-commands",
     "eval",
@@ -2186,6 +2207,7 @@ const CommandDesc evaluate_commands_cmd = {
             const bool no_hooks = context.hooks_disabled() or parser.get_switch("no-hooks");
             ScopedSetBool disable_hooks(context.hooks_disabled(), no_hooks);
 
+            LocalScope local_scope{context};
             if (parser.get_switch("verbatim"))
                 CommandManager::instance().execute_single_command(parser | gather<Vector<String>>(), context, shell_context);
             else

src/context.cc

@@ -51,8 +51,10 @@ Client& Context::client() const
     return *m_client;
 }
 
-Scope& Context::scope() const
+Scope& Context::scope(bool allow_local) const
 {
+    if (allow_local and not m_local_scopes.empty())
+        return *m_local_scopes.back();
     if (has_window())
         return window();
     if (has_buffer())
@@ -70,6 +72,8 @@ void Context::set_window(Window& window)
 {
     kak_assert(&window.buffer() == &buffer());
     m_window.reset(&window);
+    if (not m_local_scopes.empty())
+        m_local_scopes.front()->reparent(window);
 }
 
 void Context::print_status(DisplayLine status) const
@@ -314,6 +318,8 @@ void Context::change_buffer(Buffer& buffer, Optional<FunctionRef<void()>> set_se
             ScopedSelectionEdition selection_edition{*this};
             selections_write_only() = SelectionList{buffer, Selection{}};
         }
+        if (not m_local_scopes.empty())
+            m_local_scopes.front()->reparent(buffer);
     }
 
     if (has_input_handler())

src/context.hh

@@ -42,6 +42,8 @@ private:
 
 using LastSelectFunc = std::function<void (Context&)>;
 
+struct LocalScope;
+
 // A Context is used to access non singleton objects for various services
 // in commands.
 //
@@ -97,7 +99,10 @@ public:
     void set_client(Client& client);
     void set_window(Window& window);
 
-    Scope& scope() const;
+    friend struct LocalScope;
+
+    Scope& scope(bool allow_local = true) const;
+    Scope* local_scope() const { return m_local_scopes.empty() ? nullptr : m_local_scopes.back(); }
 
     OptionManager& options() const { return scope().options(); }
     HookManager&   hooks()   const { return scope().hooks(); }
@@ -155,6 +160,7 @@ private:
     SafePtr<InputHandler> m_input_handler;
     SafePtr<Window>       m_window;
     SafePtr<Client>       m_client;
+    std::vector<Scope*>   m_local_scopes;
 
     class SelectionHistory {
     public:

src/face_registry.hh

@@ -24,6 +24,8 @@ class FaceRegistry : public SafeCountable
 public:
     FaceRegistry(FaceRegistry& parent) : SafeCountable{}, m_parent(&parent) {}
 
+    void reparent(FaceRegistry& parent) { m_parent = &parent; }
+
     Face operator[](StringView facedesc) const;
     Face operator[](const FaceSpec& facespec) const;
     void add_face(StringView name, StringView facedesc, bool override = false);

src/highlighter_group.hh

@@ -43,6 +43,8 @@ class Highlighters : public SafeCountable
 public:
     Highlighters(Highlighters& parent) : SafeCountable{}, m_parent{&parent}, m_group{HighlightPass::All} {}
 
+    void reparent(Highlighters& parent) { m_parent = &parent; }
+
     HighlighterGroup& group() { return m_group; }
     const HighlighterGroup& group() const { return m_group; }
 

src/hook_manager.hh

@@ -123,6 +123,8 @@ public:
     HookManager(HookManager& parent);
     ~HookManager();
 
+    void reparent(HookManager& parent) { m_parent = &parent; }
+
     void add_hook(Hook hook, String group, HookFlags flags,
                   Regex filter, String commands, Context& context);
     void remove_hooks(const Regex& regex);

src/insert_completer.cc

@@ -403,7 +403,10 @@ InsertCompletion complete_line(const SelectionList& sels,
 }
 
 InsertCompleter::InsertCompleter(Context& context)
-    : m_context(context), m_options(context.options()), m_faces(context.faces())
+    : m_context(context),
+      // local scopes might go away before completion ends, make sure to register on a long lived one
+      m_options(context.scope(false).options()),
+      m_faces(context.scope(false).faces())
 {
     m_options.register_watcher(*this);
 }

src/keymap_manager.hh

@@ -31,6 +31,8 @@ class KeymapManager
 public:
     KeymapManager(KeymapManager& parent) : m_parent(&parent) {}
 
+    void reparent(KeymapManager& parent) { m_parent = &parent; }
+
     using KeyList = Vector<Key, MemoryDomain::Mapping>;
     void map_key(Key key, KeymapMode mode, KeyList mapping, String docstring);
     void unmap_key(Key key, KeymapMode mode);

src/option_manager.cc

@@ -28,6 +28,15 @@ OptionManager::~OptionManager()
     kak_assert(m_watchers.empty());
 }
 
+void OptionManager::reparent(OptionManager& parent)
+{
+    if (m_parent)
+        m_parent->unregister_watcher(*this);
+
+    m_parent = &parent;
+    parent.register_watcher(*this);
+}
+
 void OptionManager::register_watcher(OptionManagerWatcher& watcher) const
 {
     kak_assert(not contains(m_watchers, &watcher));

src/option_manager.hh

@@ -89,6 +89,8 @@ public:
     OptionManager(OptionManager& parent);
     ~OptionManager();
 
+    void reparent(OptionManager& parent);
+
     Option& operator[] (StringView name);
     const Option& operator[] (StringView name) const;
     Option& get_local_option(StringView name);

src/scope.cc

@@ -4,6 +4,16 @@
 namespace Kakoune
 {
 
+void Scope::reparent(Scope& parent)
+{
+    m_options.reparent(parent.m_options);
+    m_hooks.reparent(parent.m_hooks);
+    m_keymaps.reparent(parent.m_keymaps);
+    m_aliases.reparent(parent.m_aliases);
+    m_faces.reparent(parent.m_faces);
+    m_highlighters.reparent(parent.m_highlighters);
+}
+
 GlobalScope::GlobalScope()
     : m_option_registry(m_options)
 {

src/scope.hh

@@ -36,6 +36,8 @@ public:
     Highlighters&        highlighters()       { return m_highlighters; }
     const Highlighters&  highlighters() const { return m_highlighters; }
 
+    void reparent(Scope& parent);
+
 private:
     friend class GlobalScope;
     Scope() = default;