fix(paste): avoid edges cases caused by empty chunk

runtime/lua/vim/_editor.lua

@@ -128,7 +128,7 @@ local function inspect(object, options)  -- luacheck: no unused
 end
 
 do
-  local tdots, tick, got_line1 = 0, 0, false
+  local tdots, tick, got_line1, undo_started = 0, 0, false, false
 
   --- Paste handler, invoked by |nvim_paste()| when a conforming UI
   --- (such as the |TUI|) pastes text into the editor.
@@ -158,8 +158,17 @@ do
   function vim.paste(lines, phase)
     local now = vim.loop.now()
     local is_first_chunk = phase < 2
+    local is_last_chunk = phase == -1 or phase == 3
     if is_first_chunk then  -- Reset flags.
-      tdots, tick, got_line1 = now, 0, false
+      tdots, tick, got_line1, undo_started = now, 0, false, false
+    end
+    if #lines == 0 then
+      lines = {''}
+    end
+    if #lines == 1 and lines[1] == '' and not is_last_chunk then
+      -- An empty chunk can cause some edge cases in streamed pasting,
+      -- so don't do anything unless it is the last chunk.
+      return true
     end
     -- Note: mode doesn't always start with "c" in cmdline mode, so use getcmdtype() instead.
     if vim.fn.getcmdtype() ~= '' then  -- cmdline-mode: paste only 1 line.
@@ -173,7 +182,7 @@ do
       return true
     end
     local mode = vim.api.nvim_get_mode().mode
-    if not is_first_chunk then
+    if undo_started then
       vim.api.nvim_command('undojoin')
     end
     if mode:find('^i') or mode:find('^n?t') then  -- Insert mode or Terminal buffer
@@ -190,7 +199,6 @@ do
       local firstline = lines[1]
       firstline = bufline:sub(1, col)..firstline
       lines[1] = firstline
-      -- FIXME: #lines can be 0
       lines[#lines] = lines[#lines]..bufline:sub(col + nchars + 1, bufline:len())
       vim.api.nvim_buf_set_lines(0, row-1, row, false, lines)
     elseif mode:find('^[nvV\22sS\19]') then  -- Normal or Visual or Select mode
@@ -216,6 +224,7 @@ do
     else  -- Don't know what to do in other modes
       return false
     end
+    undo_started = true
     if phase ~= -1 and (now - tdots >= 100) then
       local dots = ('.'):rep(tick % 4)
       tdots = now
@@ -224,7 +233,7 @@ do
       -- message when there are zero dots.
       vim.api.nvim_command(('echo "%s"'):format(dots))
     end
-    if phase == -1 or phase == 3 then
+    if is_last_chunk then
       vim.api.nvim_command('redraw'..(tick > 1 and '|echo ""' or ''))
     end
     return true  -- Paste will not continue if not returning `true`.

test/functional/api/vim_spec.lua

@@ -630,6 +630,10 @@ describe('API', function()
   end)
 
   describe('nvim_paste', function()
+    before_each(function()
+      -- If nvim_paste() calls :undojoin without making any changes, this makes it an error.
+      feed('ifoo<Esc>u')
+    end)
     it('validates args', function()
       eq('Invalid phase: -2',
         pcall_err(request, 'nvim_paste', 'foo', true, -2))
@@ -702,7 +706,7 @@ describe('API', function()
       feed('u')
       expect('||')
     end)
-    it('stream: Visual mode either end not at the end of a line', function()
+    it('stream: Visual mode neither end at the end of a line', function()
       feed('i|xxx<CR>xxx|<Esc>hvhk')
       nvim('paste', 'aaaaaa', false, 1)
       nvim('paste', 'bbbbbb', false, 2)
@@ -714,6 +718,30 @@ describe('API', function()
         |xxx
         xxx|]])
     end)
+    it('stream: Visual mode neither end at the end of a line with empty first chunk', function()
+      feed('i|xxx<CR>xxx|<Esc>hvhk')
+      nvim('paste', '', false, 1)
+      nvim('paste', 'bbbbbb', false, 2)
+      nvim('paste', 'cccccc', false, 2)
+      nvim('paste', 'dddddd', false, 3)
+      expect('|bbbbbbccccccdddddd|')
+      feed('u')
+      expect([[
+        |xxx
+        xxx|]])
+    end)
+    it('stream: Visual mode neither end at the end of a line with all chunks empty', function()
+      feed('i|xxx<CR>xxx|<Esc>hvhk')
+      nvim('paste', '', false, 1)
+      nvim('paste', '', false, 2)
+      nvim('paste', '', false, 2)
+      nvim('paste', '', false, 3)
+      expect('||')
+      feed('u')
+      expect([[
+        |xxx
+        xxx|]])
+    end)
     it('stream: Visual mode cursor at the end of a line', function()
       feed('i||xxx<CR>xxx<Esc>vko')
       nvim('paste', 'aaaaaa', false, 1)
@@ -726,6 +754,18 @@ describe('API', function()
         ||xxx
         xxx]])
     end)
+    it('stream: Visual mode cursor at the end of a line with empty first chunk', function()
+      feed('i||xxx<CR>xxx<Esc>vko')
+      nvim('paste', '', false, 1)
+      nvim('paste', 'bbbbbb', false, 2)
+      nvim('paste', 'cccccc', false, 2)
+      nvim('paste', 'dddddd', false, 3)
+      expect('||bbbbbbccccccdddddd')
+      feed('u')
+      expect([[
+        ||xxx
+        xxx]])
+    end)
     it('stream: Visual mode other end at the end of a line', function()
       feed('i||xxx<CR>xxx<Esc>vk')
       nvim('paste', 'aaaaaa', false, 1)
@@ -738,6 +778,18 @@ describe('API', function()
         ||xxx
         xxx]])
     end)
+    it('stream: Visual mode other end at the end of a line with empty first chunk', function()
+      feed('i||xxx<CR>xxx<Esc>vk')
+      nvim('paste', '', false, 1)
+      nvim('paste', 'bbbbbb', false, 2)
+      nvim('paste', 'cccccc', false, 2)
+      nvim('paste', 'dddddd', false, 3)
+      expect('||bbbbbbccccccdddddd')
+      feed('u')
+      expect([[
+        ||xxx
+        xxx]])
+    end)
     it('non-streaming', function()
       -- With final "\n".
       nvim('paste', 'line 1\nline 2\nline 3\n', true, -1)
@@ -817,6 +869,19 @@ describe('API', function()
       eq('aabbccdd', funcs.getcmdline())
       expect('')
     end)
+    it('pasting with empty last chunk in Cmdline mode', function()
+      local screen = Screen.new(20, 4)
+      screen:attach()
+      feed(':')
+      nvim('paste', 'Foo', true, 1)
+      nvim('paste', '', true, 3)
+      screen:expect([[
+                            |
+        ~                   |
+        ~                   |
+        :Foo^                |
+      ]])
+    end)
     it('crlf=false does not break lines at CR, CRLF', function()
       nvim('paste', 'line 1\r\n\r\rline 2\nline 3\rline 4\r', false, -1)
       expect('line 1\r\n\r\rline 2\nline 3\rline 4\r')