feat(ui): "append" parameter for "msg_show" UI events

Problem:  Consecutive "msg_show" events stemming from an `:echon`
          command are supposed to be appended without a newline, this
          information is not encoded in the "msg_show" event.
Solution: Add an "append" parameter to the "msg_show" event that is set
          to true to indicate the message should not start on a new line.
Considered alternative: Emit a newline for the common case instead at the
start of a new message. That way UIs can more closely follow the logic
as it is implemented for the message grid currently. This would be a
breaking change. The "append" parameter seems OK.

runtime/doc/news.txt

@@ -141,6 +141,7 @@ EDITOR
 EVENTS
 
 • |CmdlineLeavePre| triggered before preparing to leave the command line.
+• New `append` paremeter for |ui-messages| `msg_show` event.
 
 HIGHLIGHTS
 

runtime/doc/ui.txt

@@ -810,7 +810,7 @@ will be set to zero, but can be changed and used for the replacing cmdline or
 message window. Cmdline state is emitted as |ui-cmdline| events, which the UI
 must handle.
 
-["msg_show", kind, content, replace_last, history] ~
+["msg_show", kind, content, replace_last, history, append] ~
 	Display a message to the user.
 
 	kind
@@ -860,6 +860,10 @@ must handle.
 	history
 	    True if the message was added to the |:messages| history.
 
+	append
+	    True if the message should be appeneded to the previous message,
+	    rather than started on a new line. Is set for |:echon|.
+
 ["msg_clear"] ~
 	Clear all messages currently displayed by "msg_show". (Messages sent
 	by other "msg_" events below will not be affected).

src/nvim/api/ui_events.in.h

@@ -160,7 +160,7 @@ void wildmenu_select(Integer selected)
 void wildmenu_hide(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
-void msg_show(String kind, Array content, Boolean replace_last, Boolean history)
+void msg_show(String kind, Array content, Boolean replace_last, Boolean history, Boolean append)
   FUNC_API_SINCE(6) FUNC_API_FAST FUNC_API_REMOTE_ONLY;
 void msg_clear(void)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;

src/nvim/eval.c

@@ -7863,6 +7863,7 @@ void ex_echo(exarg_T *eap)
       char *tofree = encode_tv2echo(&rettv, NULL);
       if (*tofree != NUL) {
         msg_ext_set_kind("echo");
+        msg_ext_append = eap->cmdidx == CMD_echon;
         msg_multiline(cstr_as_string(tofree), echo_hl_id, true, false, &need_clear);
       }
       xfree(tofree);

src/nvim/message.c

@@ -3185,7 +3185,8 @@ void msg_ext_ui_flush(void)
   msg_ext_emit_chunk();
   if (msg_ext_chunks->size > 0) {
     Array *tofree = msg_ext_init_chunks();
-    ui_call_msg_show(cstr_as_string(msg_ext_kind), *tofree, msg_ext_overwrite, msg_ext_history);
+    ui_call_msg_show(cstr_as_string(msg_ext_kind), *tofree, msg_ext_overwrite, msg_ext_history,
+                     msg_ext_append);
     if (msg_ext_history || strequal(msg_ext_kind, "return_prompt")) {
       api_free_array(*tofree);
     } else {
@@ -3205,6 +3206,7 @@ void msg_ext_ui_flush(void)
     }
     msg_ext_overwrite = false;
     msg_ext_history = false;
+    msg_ext_append = false;
     msg_ext_kind = NULL;
   }
 }

src/nvim/message.h

@@ -33,6 +33,8 @@ extern MessageHistoryEntry *msg_hist_last;
 EXTERN bool msg_ext_need_clear INIT( = false);
 // Set to true to force grouping a set of message chunks into a single `cmdline_show` event.
 EXTERN bool msg_ext_skip_flush INIT( = false);
+// Set to true when message should be appended to previous message line.
+EXTERN bool msg_ext_append INIT( = false);
 
 /// allocated grid for messages. Used unless ext_messages is active.
 /// See also the description at msg_scroll_flush()

test/functional/lua/ui_event_spec.lua

@@ -221,7 +221,6 @@ describe('vim.ui_attach', function()
       messages = {
         {
           content = { { '\nSave changes?\n', 6, 10 } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -477,7 +476,6 @@ describe('vim.ui_attach', function()
         },
         {
           content = { { 'Press ENTER or type command to continue', 100, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -530,7 +528,6 @@ describe('vim.ui_attach', function()
         },
         {
           content = { { 'Press ENTER or type command to continue', 100, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },

test/functional/ui/messages_spec.lua

@@ -60,7 +60,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { '\ntest\n', 6, 10 } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -92,7 +91,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { '\ntest\n', 6, 10 } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -104,17 +102,14 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { '\ntest\n', 6, 10 } },
-          history = false,
           kind = 'confirm',
         },
         {
           content = { { '1' } },
-          history = false,
           kind = 'echo',
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -214,7 +209,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { '?line ' } },
-          history = false,
           kind = 'search_cmd',
         },
       },
@@ -238,7 +232,6 @@ describe('ui/ext_messages', function()
             { 'links to', 18, 5 },
             { ' SpecialChar' },
           },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -285,7 +278,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'The only match' } },
-          history = false,
           kind = 'completion',
         },
       },
@@ -337,12 +329,10 @@ describe('ui/ext_messages', function()
             { 'guibg=', 18, 5 },
             { 'LightBlue' },
           },
-          history = false,
           kind = 'list_cmd',
         },
         {
           content = { { '\n\tLast set from Lua (run Nvim with -V1 for more details)' } },
-          history = false,
           kind = 'verbose',
         },
         {
@@ -355,17 +345,14 @@ describe('ui/ext_messages', function()
             { 'guibg=', 18, 5 },
             { 'LightMagenta' },
           },
-          history = false,
           kind = 'list_cmd',
         },
         {
           content = { { '\n\tLast set from Lua (run Nvim with -V1 for more details)' } },
-          history = false,
           kind = 'verbose',
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -406,7 +393,6 @@ describe('ui/ext_messages', function()
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -462,27 +448,22 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { (':!%s\r\n[No write since last change]\n'):format(cmd) } },
-          history = false,
           kind = 'shell_cmd',
         },
         {
           content = { { ('stdout%s\n'):format(t.is_os('win') and '\r' or '') } },
-          history = false,
           kind = 'shell_out',
         },
         {
           content = { { ('stderr%s\n'):format(t.is_os('win') and '\r' or ''), 9, 71 } },
-          history = false,
           kind = 'shell_err',
         },
         {
           content = { { '\nshell returned 3\n\n' } },
-          history = false,
           kind = 'shell_ret',
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -497,7 +478,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { '\nType Name Content', 101, 23 }, { '\n  c  ".   ' } },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -517,7 +497,6 @@ describe('ui/ext_messages', function()
             { 'ChanInfo', 101, 23 },
             { '\n*foo' },
           },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -534,7 +513,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'line 1\nline ' } },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -592,7 +570,6 @@ describe('ui/ext_messages', function()
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -623,7 +600,6 @@ describe('ui/ext_messages', function()
         },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -688,7 +664,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -731,7 +706,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -757,7 +731,7 @@ describe('ui/ext_messages', function()
     ]],
       cmdline = { { abort = false } },
       messages = {
-        { content = { { '/line      W [1/2]' } }, kind = 'search_count', history = false },
+        { content = { { '/line      W [1/2]' } }, kind = 'search_count' },
       },
     }
 
@@ -769,7 +743,7 @@ describe('ui/ext_messages', function()
       {1:~                        }|*3
     ]],
       messages = {
-        { content = { { '/line        [2/2]' } }, kind = 'search_count', history = false },
+        { content = { { '/line        [2/2]' } }, kind = 'search_count' },
       },
     }
   end)
@@ -784,11 +758,10 @@ describe('ui/ext_messages', function()
     ]],
       cmdline = { { abort = false } },
       messages = {
-        { content = { { 'x                     #1' } }, kind = 'list_cmd', history = false },
+        { content = { { 'x                     #1' } }, kind = 'list_cmd' },
-        { content = { { 'y                     #2' } }, kind = 'list_cmd', history = false },
+        { content = { { 'y                     #2' } }, kind = 'list_cmd' },
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -908,7 +881,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -1156,7 +1128,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'xyz' } },
-          history = false,
           kind = 'echo',
         },
       },
@@ -1194,7 +1165,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -1326,7 +1296,6 @@ stack traceback:
             { '*', 18, 1 },
             { ' k' },
           },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -1347,7 +1316,6 @@ stack traceback:
       messages = {
         {
           content = { { 'wildmenu  wildmode\n' } },
-          history = false,
           kind = 'wildlist',
         },
       },
@@ -1382,7 +1350,6 @@ stack traceback:
       messages = {
         {
           content = { { 'Change "helllo" to:\n 1 "Hello"\n 2 "Hallo"\n 3 "Hullo"' } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -1405,7 +1372,6 @@ stack traceback:
       messages = {
         {
           content = { { 'Change "helllo" to:\n 1 "Hello"\n 2 "Hallo"\n 3 "Hullo"' } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -1437,7 +1403,6 @@ stack traceback:
       messages = {
         {
           content = { { 'input0\ninput1' } },
-          history = false,
           kind = 'confirm',
         },
       },
@@ -1487,7 +1452,6 @@ stack traceback:
         {
           content = { { '\n  1 %a   "[No Name]"                    line 1' } },
           kind = 'list_cmd',
-          history = false,
         },
       },
     }
@@ -1502,7 +1466,6 @@ stack traceback:
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -1631,11 +1594,7 @@ stack traceback:
         {1:~                        }|*4
       ]],
       messages = {
-        {
+        { content = { { 'bar' } }, kind = 'echo' },
-          content = { { 'bar' } },
-          history = false,
-          kind = 'echo',
-        },
       },
     })
     feed('g<lt>')
@@ -1647,7 +1606,6 @@ stack traceback:
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -1685,7 +1643,6 @@ stack traceback:
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -1708,7 +1665,6 @@ stack traceback:
       messages = {
         {
           content = { { '  shiftwidth=8\n  tabstop=8\n  softtabstop=0' } },
-          history = false,
           kind = 'list_cmd',
         },
       },
@@ -1730,6 +1686,25 @@ stack traceback:
       {1:~                        }|*4
     ]])
   end)
+
+  it(':echon sets append', function()
+    command('echo "foo" | echon " bar" | echon " baz"')
+    screen:expect({
+      grid = [[
+        ^                         |
+        {1:~                        }|*4
+      ]],
+      messages = {
+        { content = { { 'foo' } }, kind = 'echo' },
+        { content = { { ' bar' } }, kind = 'echo', append = true },
+        { content = { { ' baz' } }, kind = 'echo', append = true },
+        {
+          content = { { 'Press ENTER or type command to continue', 6, 18 } },
+          kind = 'return_prompt',
+        },
+      },
+    })
+  end)
 end)
 
 describe('ui/builtin messages', function()
@@ -2394,7 +2369,6 @@ describe('ui/ext_messages', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
           kind = 'return_prompt',
         },
       },
@@ -2476,7 +2450,7 @@ describe('ui/ext_messages', function()
     ]],
       cmdline = { { abort = false } },
       messages = {
-        { content = { { '  cmdheight=0' } }, kind = 'list_cmd', history = false },
+        { content = { { '  cmdheight=0' } }, kind = 'list_cmd' },
       },
     })
 
@@ -2493,7 +2467,7 @@ describe('ui/ext_messages', function()
     ]],
       cmdline = { { abort = false } },
       messages = {
-        { content = { { '  laststatus=3' } }, kind = 'list_cmd', history = false },
+        { content = { { '  laststatus=3' } }, kind = 'list_cmd' },
       },
     })
 
@@ -2514,7 +2488,7 @@ describe('ui/ext_messages', function()
     ]],
       cmdline = { { abort = false } },
       messages = {
-        { content = { { '  cmdheight=0' } }, kind = 'list_cmd', history = false },
+        { content = { { '  cmdheight=0' } }, kind = 'list_cmd' },
       },
     })
   end)

test/functional/ui/screen.lua

@@ -1383,12 +1383,12 @@ function Screen:_handle_wildmenu_hide()
   self.wildmenu_items, self.wildmenu_pos = nil, nil
 end
 
-function Screen:_handle_msg_show(kind, chunks, replace_last, history)
+function Screen:_handle_msg_show(kind, chunks, replace_last, history, append)
   local pos = #self.messages
   if not replace_last or pos == 0 then
     pos = pos + 1
   end
-  self.messages[pos] = { kind = kind, content = chunks, history = history }
+  self.messages[pos] = { kind = kind, content = chunks, history = history, append = append }
 end
 
 function Screen:_handle_msg_clear()
@@ -1507,7 +1507,8 @@ function Screen:_extstate_repr(attr_state)
     messages[i] = {
       kind = entry.kind,
       content = self:_chunks_repr(entry.content, attr_state),
-      history = entry.history,
+      history = entry.history or nil,
+      append = entry.append or nil,
     }
   end