feat(editor)!: insert-mode ctrl-r should work like paste #35477

Problem:
insert-mode ctrl-r input is treated like raw user input, which is almost
never useful. This means any newlines in the input are affected by
autoindent, etc., which is:
- slow
- usually breaks the formatting of the input

Solution:
- ctrl-r should be treated like a paste, not user-input.
- does not affect `<c-r>=`, so `<c-r>=@x` can still be used to get the
  old behavior.

Co-authored-by: Justin M. Keyes <justinkz@gmail.com>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>

runtime/doc/cmdline.txt

@@ -142,13 +142,16 @@ CTRL-R {register}					*c_CTRL-R* *c_<C-R>*
 		typing CTRL-R and the second character '"' will be displayed
 		to indicate that you are expected to enter the name of a
 		register.
-		The text is inserted as if you typed it, but mappings and
+		When used with named or clipboard registers (A-Z,a-z,0-9,+)
-		abbreviations are not used.  Command-line completion through
+		text is inserted literally like pasting with "p". For other
-		'wildchar' is not triggered though.  And characters that end
+		registers, the text is inserted as if you typed it, but
-		the command line are inserted literally (<Esc>, <CR>, <NL>,
+		mappings and abbreviations are not used. Command-line
-		<C-C>).  A <BS> or CTRL-W could still end the command line
+		completion through 'wildchar' is not triggered though.  And
-		though, and remaining characters will then be interpreted in
+		characters that end the command line are inserted literally
-		another mode, which might not be what you intended.
+		(<Esc>, <CR>, <NL>, <C-C>).  A <BS> or CTRL-W could still end
+		the command line though, and remaining characters will then be
+		interpreted in another mode, which might not be what you
+		intended.
 		Special registers:
 			'"'	the unnamed register, containing the text of
 				the last delete or yank
@@ -176,7 +179,9 @@ CTRL-R {register}					*c_CTRL-R* *c_<C-R>*
 				sure the expression evaluates to an empty
 				string.  E.g.: >
 					<C-R><C-R>=setcmdpos(2)[-1]<CR>
-<		See |registers| about registers.
+<				You can use this to insert a register as
+				typed with CTRL-R =@reg.
+		See |registers| about registers.
 		Implementation detail: When using the |expression| register
 		and invoking setcmdpos(), this sets the position before
 		inserting the resulting string.  Use CTRL-R CTRL-R to set the

runtime/doc/insert.txt

@@ -103,12 +103,15 @@ CTRL-P		Find previous keyword (see |i_CTRL-P|).
 CTRL-R {register}				*i_CTRL-R*
 		Insert the contents of a register. Between typing CTRL-R and
 		the second character, '"' will be displayed to indicate that
-		you are expected to enter the name of a register.
+		you are expected to enter the name of a register. When used
-		The text is inserted as if you typed it, but mappings and
+		with When used with named or clipboard registers
-		abbreviations are not used.  If you have options like
+		(A-Z,a-z,0-9,+) text is inserted literally like pasting with
-		'textwidth', 'formatoptions', or 'autoindent' set, this will
+		"p". For other registers, the text is inserted as if you typed
-		influence what will be inserted.  This is different from what
+		it, but mappings and abbreviations are not used.  If you have
-		happens with the "p" command and pasting with the mouse.
+		options like 'textwidth', 'formatoptions', or 'autoindent'
+		set, this will influence what will be inserted. This is
+		different from what happens with the "p" command and pasting
+		with the mouse.
 		Special registers:
 			'"'	the unnamed register, containing the text of
 				the last delete or yank
@@ -131,6 +134,8 @@ CTRL-R {register}				*i_CTRL-R*
 				special keys.  E.g., you can use this to move
 				the cursor up:
 					CTRL-R ="\<Up>"
+				you can use this to insert a register as
+				typed with CTRL-R =@reg.
 				Use CTRL-R CTRL-R to insert text literally.
 				When the result is a |List| the items are used
 				as lines.  They can have line breaks inside

runtime/doc/news.txt

@@ -68,7 +68,8 @@ DIAGNOSTICS
 
 EDITOR
 
-• todo
+• |i_CTRL-R| inserts named registers (A-Z,a-z,0-9) literally like pasting instead of
+  as typed. To get the old behavior you can use `<C-R>=@x`.
 
 EVENTS
 

runtime/doc/vim_diff.txt

@@ -316,6 +316,8 @@ Commands:
 Editor:
 - |prompt-buffer| supports multiline input/paste, undo/redo, and o/O normal
   commands.
+- |i_CTRL-R| inserts named registers (A-Z,a-z,0-9) literally like pasting instead of
+  as typed. To get the old behavior you can use `<C-R>=@x`.
 
 Events (autocommands):
 - Fixed inconsistent behavior in execution of nested autocommands #23368

src/nvim/edit.c

@@ -2854,6 +2854,8 @@ static void ins_reg(void)
     vim_beep(kOptBoFlagRegister);
     need_redraw = true;  // remove the '"'
   } else {
+    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
+
     if (literally == Ctrl_O || literally == Ctrl_P) {
       // Append the command to the redo buffer.
       AppendCharToRedobuff(Ctrl_R);
@@ -2862,7 +2864,11 @@ static void ins_reg(void)
 
       do_put(regname, NULL, BACKWARD, 1,
              (literally == Ctrl_P ? PUT_FIXINDENT : 0) | PUT_CURSEND);
-    } else if (insert_reg(regname, NULL, literally) == FAIL) {
+    } else if (reg->y_size > 1 && is_literal_register(regname)) {
+      AppendCharToRedobuff(Ctrl_R);
+      AppendCharToRedobuff(regname);
+      do_put(regname, NULL, BACKWARD, 1, PUT_CURSEND);
+    } else if (insert_reg(regname, NULL, !!literally) == FAIL) {
       vim_beep(kOptBoFlagRegister);
       need_redraw = true;  // remove the '"'
     } else if (stop_insert_mode) {

src/nvim/ops.h

@@ -152,7 +152,7 @@ static inline int op_reg_index(const int regname)
 static inline bool is_literal_register(const int regname)
   FUNC_ATTR_CONST
 {
-  return regname == '*' || regname == '+';
+  return regname == '*' || regname == '+' || ASCII_ISALNUM(regname);
 }
 
 EXTERN LuaRef repeat_luaref INIT( = LUA_NOREF);  ///< LuaRef for "."

test/functional/editor/mode_insert_spec.lua

@@ -83,6 +83,36 @@ describe('insert-mode', function()
         {5:-- INSERT --}                                      |
       ]])
     end)
+
+    it('inserts named registers literally', function()
+      local screen = Screen.new(50, 6)
+      -- regular text without special charecter command
+      command('let @a = "test"')
+      feed('i<C-R>a<ESC>')
+      screen:expect([[
+        tes^t                                              |
+        {1:~                                                 }|*4
+                                                          |
+      ]])
+
+      -- text with backspace character gets written literally by default
+      command('let @a = "test\\<C-H>"')
+      feed('cc<C-R>a<ESC>')
+      screen:expect([[
+        test{18:^^H}                                            |
+        {1:~                                                 }|*4
+                                                          |
+      ]])
+
+      -- =@reg<CR> can be used to get effect of keypress
+      command('let @a = "test\\<C-H>"')
+      feed('cc<C-R>=@a<CR><ESC>')
+      screen:expect([[
+        te^s                                               |
+        {1:~                                                 }|*4
+                                                          |
+      ]])
+    end)
   end)
 
   describe('Ctrl-O', function()

test/old/testdir/test_autocmd.vim

@@ -2090,7 +2090,7 @@ func Test_Cmdline()
 
   let g:log = []
   let @r = 'abc'
-  call feedkeys(":0\<C-R>r1\<C-R>\<C-O>r2\<C-R>\<C-R>r3\<Esc>", 'xt')
+  call feedkeys(":0\<C-R>=@r\<CR>1\<C-R>\<C-O>r2\<C-R>\<C-R>r3\<Esc>", 'xt')
   call assert_equal([
         \ '0',
         \ '0a',

test/old/testdir/test_cmdline.vim

@@ -905,7 +905,7 @@ func Test_cmdline_paste()
 
   " Test for pasting register containing CTRL-H using CTRL-R and CTRL-R CTRL-R
   let @a = "xy\<C-H>z"
-  call feedkeys(":\"\<C-R>a\<CR>", 'xt')
+  call feedkeys(":\"\<C-R>=@a\<CR>\<CR>", 'xt')
   call assert_equal('"xz', @:)
   call feedkeys(":\"\<C-R>\<C-R>a\<CR>", 'xt')
   call assert_equal("\"xy\<C-H>z", @:)

test/old/testdir/test_ins_complete.vim

@@ -1523,7 +1523,7 @@ func Test_complete_reginsert()
   exe "normal Goa\<C-P>\<C-R>=\"\\<C-P>\"\<CR>"
   call assert_equal('a123', getline(5))
   let @r = "\<C-P>\<C-P>"
-  exe "normal GCa\<C-P>\<C-R>r"
+  exe "normal GCa\<C-P>\<C-R>=@r\<CR>"
   call assert_equal('a12', getline(5))
   exe "normal GCa\<C-P>\<C-R>=\"x\"\<CR>"
   call assert_equal('a1234x', getline(5))