Use main selection index as default when accessing only one register value

Fixes #117

src/command_manager.cc

@@ -316,7 +316,7 @@ String eval_token(const Token& token, Context& context,
         return ShellManager::instance().eval(content, context, shell_params,
                                              env_vars);
     case Token::Type::RegisterExpand:
-        return RegisterManager::instance()[content].values(context)[0];
+        return context.main_sel_register_value(content);
     case Token::Type::OptionExpand:
         return context.options()[content].get_as_string();
     case Token::Type::ValExpand:

src/context.cc

@@ -2,6 +2,7 @@
 
 #include "client.hh"
 #include "user_interface.hh"
+#include "register_manager.hh"
 #include "window.hh"
 
 namespace Kakoune
@@ -226,4 +227,13 @@ void Context::end_edition()
     --m_edition_level;
 }
 
+StringView Context::main_sel_register_value(StringView reg) const
+{
+    auto strings = RegisterManager::instance()[reg].values(*this);
+    size_t index = m_selections ? (*m_selections).main_index() : 0;
+    if (strings.size() < index)
+        index = strings.size() - 1;
+   return strings[index];
+}
+
 }

src/context.hh

@@ -64,6 +64,8 @@ public:
 
     void print_status(DisplayLine status) const;
 
+    StringView main_sel_register_value(StringView reg) const;
+
     void push_jump();
     const SelectionList& jump_forward();
     const SelectionList& jump_backward();

src/highlighters.cc

@@ -358,10 +358,10 @@ HighlighterAndId highlight_search_factory(HighlighterParameters params)
             return ColorSpec{ { 0, &Kakoune::get_color("Search") } };
         };
         auto get_regex = [](const Context&){
-            auto s = RegisterManager::instance()['/'].values(Context{});
+            auto s = Context().main_sel_register_value("/");
             try
             {
-                return s.empty() ? Regex{} : Regex{s[0].begin(), s[0].end()};
+                return s.empty() ? Regex{} : Regex{s.begin(), s.end()};
             }
             catch (boost::regex_error& err)
             {

src/input_handler.cc

@@ -374,7 +374,7 @@ public:
 
         if (m_mode == Mode::InsertReg)
         {
-            String reg = RegisterManager::instance()[key.key].values(context())[0];
+            StringView reg = context().main_sel_register_value(String{key.key});
             m_line_editor.insert(reg);
             m_mode = Mode::Default;
         }

src/main.cc

@@ -106,7 +106,7 @@ void register_env_vars()
         }, {
             "reg_.+",
             [](StringView name, const Context& context) -> String
-            { return RegisterManager::instance()[name.substr(4_byte)].values(context)[0]; }
+            { return context.main_sel_register_value(name.substr(4_byte)); }
         }, {
             "client_env_.+",
             [](StringView name, const Context& context) -> String

src/normal.cc

@@ -384,9 +384,9 @@ void pipe(Context& context, int)
             if (event != PromptEvent::Validate)
                 return;
 
-            String real_cmd;
+            StringView real_cmd;
             if (cmdline.empty())
-                real_cmd = RegisterManager::instance()['|'].values(context)[0];
+                real_cmd = context.main_sel_register_value("|");
             else
             {
                 RegisterManager::instance()['|'] = cmdline;
@@ -575,7 +575,7 @@ void search(Context& context, int)
     regex_prompt(context, direction == Forward ? "search:" : "reverse search:",
                  [](Regex ex, Context& context) {
                      if (ex.empty())
-                         ex = Regex{RegisterManager::instance()['/'].values(context)[0]};
+                         ex = Regex{context.main_sel_register_value("/").str()};
                      else
                          RegisterManager::instance()['/'] = String{ex.str()};
                      if (not ex.empty() and not ex.str().empty())
@@ -586,12 +586,12 @@ void search(Context& context, int)
 template<SelectMode mode, Direction direction>
 void search_next(Context& context, int param)
 {
-    const String& str = RegisterManager::instance()['/'].values(context)[0];
+    StringView str = context.main_sel_register_value("/");
     if (not str.empty())
     {
         try
         {
-            Regex ex{str};
+            Regex ex{str.begin(), str.end()};
             do {
                 select_next_match<direction, mode>(context.buffer(), context.selections(), ex);
             } while (--param > 0);
@@ -632,7 +632,7 @@ void select_regex(Context& context, int)
 {
     regex_prompt(context, "select:", [](Regex ex, Context& context) {
         if (ex.empty())
-            ex = Regex{RegisterManager::instance()['/'].values(context)[0]};
+            ex = Regex{context.main_sel_register_value("/").str()};
         else
             RegisterManager::instance()['/'] = String{ex.str()};
         if (not ex.empty() and not ex.str().empty())
@@ -644,7 +644,7 @@ void split_regex(Context& context, int)
 {
     regex_prompt(context, "split:", [](Regex ex, Context& context) {
         if (ex.empty())
-            ex = Regex{RegisterManager::instance()['/'].values(context)[0]};
+            ex = Regex{context.main_sel_register_value("/").str()};
         else
             RegisterManager::instance()['/'] = String{ex.str()};
         if (not ex.empty() and not ex.str().empty())