fix(messages): proper multiline Lua print() messages #31205

Problem:  Separate message emitted for each newline present in Lua
          print() arguments.
Solution: Make msg_multiline() handle NUL bytes. Refactor print() to use
          msg_multiline(). Refactor vim.print() to use print().

3 files changed, 33 insertions, 10 deletions

diff --git a/test/functional/core/startup_spec.lua b/test/functional/core/startup_spec.lua
index e885164c20..7062211187 100644
--- a/test/functional/core/startup_spec.lua
+++ b/test/functional/core/startup_spec.lua
@@ -277,10 +277,8 @@ describe('startup', function()
 
       -- nvim <vim args> -l foo.lua <vim args>
       assert_l_out(
-        -- luacheck: ignore 611 (Line contains only whitespaces)
         [[
             wrap
-          
           bufs:
           nvim args: 7
           lua args: { "-c", "set wrap?",
diff --git a/test/functional/lua/ui_event_spec.lua b/test/functional/lua/ui_event_spec.lua
index 6d4be4d1f2..c8616e3e11 100644
--- a/test/functional/lua/ui_event_spec.lua
+++ b/test/functional/lua/ui_event_spec.lua
@@ -142,7 +142,7 @@ describe('vim.ui_attach', function()
         'msg_history_show',
         {
           { 'echomsg', { { 0, 'message1', 0 } } },
-          { '', { { 0, 'message2', 0 } } },
+          { 'lua_print', { { 0, 'message2', 0 } } },
           { 'echomsg', { { 0, 'message3', 0 } } },
         },
       },
diff --git a/test/functional/ui/messages_spec.lua b/test/functional/ui/messages_spec.lua
index 25f3465d46..734877d262 100644
--- a/test/functional/ui/messages_spec.lua
+++ b/test/functional/ui/messages_spec.lua
@@ -1113,6 +1113,33 @@ stack traceback:
     })
     eq(showmode, 1)
   end)
+
+  it('emits single message for multiline print())', function()
+    exec_lua([[print("foo\nbar\nbaz")]])
+    screen:expect({
+      messages = {
+        {
+          content = { { 'foo\nbar\nbaz' } },
+          kind = 'lua_print',
+        },
+      },
+    })
+    exec_lua([[print(vim.inspect({ foo = "bar" }))]])
+    screen:expect({
+      grid = [[
+        ^                         |
+        {1:~                        }|*4
+      ]],
+      messages = {
+        {
+          content = { { '{\n  foo = "bar"\n}' } },
+          kind = 'lua_print',
+        },
+      },
+    })
+    exec_lua([[vim.print({ foo = "bar" })]])
+    screen:expect_unchanged()
+  end)
 end)
 
 describe('ui/builtin messages', function()
@@ -2062,8 +2089,6 @@ aliquip ex ea commodo consequat.]]
   end)
 
   it('can be quit with Lua #11224 #16537', function()
-    -- NOTE: adds "4" to message history, although not displayed initially
-    --       (triggered the more prompt).
     screen:try_resize(40, 5)
     feed(':lua for i=0,10 do print(i) end<cr>')
     screen:expect {
@@ -2093,13 +2118,13 @@ aliquip ex ea commodo consequat.]]
       {4:-- More --}^                              |
     ]],
     }
-    feed('j')
+    feed('G')
     screen:expect {
       grid = [[
-      1                                       |
-      2                                       |
-      3                                       |
-      4                                       |
+      7                                       |
+      8                                       |
+      9                                       |
+      10                                      |
       {4:Press ENTER or type command to continue}^ |
     ]],
     }