Merge pull request #18248 from zeertzjq/vim-8.2.4806

vim-patch:8.2.{4806,4818}: a mapping using <LeftDrag> does not start Select mode

src/nvim/normal.c

@@ -5740,10 +5740,10 @@ void start_selection(void)
 }
 
 /// Start Select mode, if "c" is in 'selectmode' and not in a mapping or menu.
+/// When "c" is 'o' (checking for "mouse") then also when mapped.
 void may_start_select(int c)
 {
-  VIsual_select = (stuff_empty() && typebuf_typed()
+  VIsual_select = (c == 'o' || (stuff_empty() && typebuf_typed())) && vim_strchr(p_slm, c) != NULL;
-                   && (vim_strchr(p_slm, c) != NULL));
 }
 
 /// Start Visual mode "c".

src/nvim/testdir/test_mapping.vim

@@ -676,6 +676,35 @@ func Test_plug_remap()
   %bw!
 endfunc
 
+func Test_mouse_drag_mapped_start_select()
+  CheckFunction test_setmouse
+  set mouse=a
+  set selectmode=key,mouse
+  func ClickExpr()
+    call test_setmouse(1, 1)
+    return "\<LeftMouse>"
+  endfunc
+  func DragExpr()
+    call test_setmouse(1, 2)
+    return "\<LeftDrag>"
+  endfunc
+  nnoremap <expr> <F2> ClickExpr()
+  nmap <expr> <F3> DragExpr()
+
+  nnoremap <LeftDrag> <LeftDrag><Cmd><CR>
+  exe "normal \<F2>\<F3>"
+  call assert_equal('s', mode())
+  exe "normal! \<C-\>\<C-N>"
+
+  nunmap <LeftDrag>
+  nunmap <F2>
+  nunmap <F3>
+  delfunc ClickExpr
+  delfunc DragExpr
+  set selectmode&
+  set mouse&
+endfunc
+
 " Test for mapping <LeftDrag> in Insert mode
 func Test_mouse_drag_insert_map()
   CheckFunction test_setmouse

test/functional/legacy/mapping_spec.lua

@@ -129,10 +129,23 @@ describe('mapping', function()
       ]])
   end)
 
+  it('dragging starts Select mode even if coming from mapping vim-patch:8.2.4806', function()
+    command('set mouse=a')
+    command('set selectmode=mouse')
+
+    command('nnoremap <LeftDrag> <LeftDrag><Cmd><CR>')
+    sleep(10)
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    sleep(10)
+    meths.input_mouse('left', 'drag', '', 0, 0, 1)
+    sleep(10)
+    eq('s', eval('mode()'))
+  end)
+
   it('<LeftDrag> mapping in Insert mode works correctly vim-patch:8.2.4692', function()
     command('set mouse=a')
 
-    command([[inoremap <LeftDrag> <LeftDrag><Cmd>let g:dragged = 1<CR>]])
+    command('inoremap <LeftDrag> <LeftDrag><Cmd>let g:dragged = 1<CR>')
     feed('i')
     sleep(10)
     meths.input_mouse('left', 'press', '', 0, 0, 0)