Support discarding selections in exec/eval -itersel

Only fail if all selections are discarded.
Fixes #2841

src/commands.cc

@@ -1782,18 +1782,22 @@ void context_wrap(const ParametersParser& parser, Context& context, StringView d
         Vector<Selection> new_sels;
         size_t main = 0;
         size_t timestamp = c.buffer().timestamp();
+        bool one_selection_succeeded = false;
         for (auto& sel : sels)
         {
             c.selections_write_only() = SelectionList{sels.buffer(), sel, sels.timestamp()};
             c.selections().update();
 
-            func(parser, c);
-
-            if (not draft)
+            try
             {
+                func(parser, c);
+                one_selection_succeeded = true;
+
                 if (&sels.buffer() != &c.buffer())
                     throw runtime_error("buffer has changed while iterating on selections");
 
+                if (not draft)
+                {
                     update_selections(new_sels, main, c.buffer(), timestamp);
                     timestamp = c.buffer().timestamp();
                     if (&sel == &sels.main())
@@ -1803,6 +1807,14 @@ void context_wrap(const ParametersParser& parser, Context& context, StringView d
                     std::inplace_merge(new_sels.begin(), middle, new_sels.end(), compare_selections);
                 }
             }
+            catch (no_selections_remaining&) {}
+        }
+
+        if (not one_selection_succeeded)
+        {
+            c.selections_write_only() = std::move(sels);
+            throw no_selections_remaining{};
+        }
 
         if (not draft)
             c.selections_write_only().set(std::move(new_sels), main);

src/normal.cc

@@ -113,7 +113,7 @@ void select(Context& context, T func)
         }
 
         if (to_remove.size() == selections.size())
-            throw runtime_error{"no selections remaining"};
+            throw no_selections_remaining{};
         for (auto& i : to_remove | reverse())
             selections.remove(i);
     }
@@ -1135,7 +1135,7 @@ void keep(Context& context, NormalParams params)
                 keep.push_back(sel);
         }
         if (keep.empty())
-            throw runtime_error("no selections remaining");
+            throw no_selections_remaining{};
         context.selections_write_only() = std::move(keep);
     });
 }
@@ -1168,7 +1168,7 @@ void keep_pipe(Context& context, NormalParams)
                 }
             }
             if (keep.empty())
-                throw runtime_error("no selections remaining");
+                throw no_selections_remaining{};
             if (new_main == -1)
                 new_main = keep.size() - 1;
             context.selections_write_only().set(std::move(keep), new_main);
@@ -1775,7 +1775,7 @@ void trim_selections(Context& context, NormalParams)
     }
 
     if (to_remove.size() == selections.size())
-        throw runtime_error{"no selections remaining"};
+        throw no_selections_remaining{};
     for (auto& i : to_remove | reverse())
         selections.remove(i);
 }

src/normal.hh

@@ -5,12 +5,18 @@
 #include "keys.hh"
 #include "keymap_manager.hh"
 #include "string.hh"
+#include "exception.hh"
 
 namespace Kakoune
 {
 
 class Context;
 
+struct no_selections_remaining : runtime_error
+{
+    no_selections_remaining() : runtime_error("no selections remaining") {}
+};
+
 struct NormalParams
 {
     int count;

test/compose/discard-selections-with-itersel/cmd

@@ -0,0 +1 @@
+:exec -itersel <lt>a-k>ba<lt>ret><ret>d

test/compose/discard-selections-with-itersel/in

@@ -0,0 +1,3 @@
+%(foo)
+%(bar)
+%(baz)

test/compose/discard-selections-with-itersel/out

@@ -0,0 +1,3 @@
+foo
+
+