test: add some tests for :*map <expr>

Add tests for:
 - Cursor position restored after :map expr
 - Cursor position restored after :imap expr
 - Error in :cmap expr handled correctly

Cherry-picked from #12837

test/functional/ex_cmds/map_spec.lua

@@ -1,4 +1,5 @@
 local helpers = require("test.functional.helpers")(after_each)
+local Screen = require('test.functional.ui.screen')
 
 local eq = helpers.eq
 local feed = helpers.feed
@@ -26,3 +27,104 @@ describe(':*map', function()
     expect('-foo-')
   end)
 end)
+
+describe(':*map <expr>', function()
+  local screen
+  before_each(function()
+    clear()
+    screen = Screen.new(20, 5)
+    screen:attach()
+  end)
+
+  it('cursor is restored after :map <expr>', function()
+    command(':map <expr> x input("> ")')
+    screen:expect([[
+      ^                    |
+      ~                   |
+      ~                   |
+      ~                   |
+                          |
+    ]])
+    feed('x')
+    screen:expect([[
+                          |
+      ~                   |
+      ~                   |
+      ~                   |
+      > ^                  |
+    ]])
+    feed('\n')
+    screen:expect([[
+      ^                    |
+      ~                   |
+      ~                   |
+      ~                   |
+      >                   |
+    ]])
+  end)
+
+  it('cursor is restored after :imap <expr>', function()
+    command(':imap <expr> x input("> ")')
+    feed('i')
+    screen:expect([[
+      ^                    |
+      ~                   |
+      ~                   |
+      ~                   |
+      -- INSERT --        |
+    ]])
+    feed('x')
+    screen:expect([[
+                          |
+      ~                   |
+      ~                   |
+      ~                   |
+      > ^                  |
+    ]])
+    feed('\n')
+    screen:expect([[
+      ^                    |
+      ~                   |
+      ~                   |
+      ~                   |
+      >                   |
+    ]])
+  end)
+
+  it('error in :cmap <expr> handled correctly', function()
+    screen:try_resize(40, 5)
+    command(':cmap <expr> x execute("throw 42")')
+    feed(':echo "foo')
+    screen:expect([[
+                                              |
+      ~                                       |
+      ~                                       |
+      ~                                       |
+      :echo "foo^                              |
+    ]])
+    feed('x')
+    screen:expect([[
+                                              |
+      :echo "foo                              |
+      Error detected while processing :       |
+      E605: Exception not caught: 42          |
+      :echo "foo^                              |
+    ]])
+    feed('"')
+    screen:expect([[
+                                              |
+      :echo "foo                              |
+      Error detected while processing :       |
+      E605: Exception not caught: 42          |
+      :echo "foo"^                             |
+    ]])
+    feed('\n')
+    screen:expect([[
+      :echo "foo                              |
+      Error detected while processing :       |
+      E605: Exception not caught: 42          |
+      foo                                     |
+      Press ENTER or type command to continue^ |
+    ]])
+  end)
+end)

test/functional/ui/cmdline_highlight_spec.lua

@@ -33,7 +33,7 @@ before_each(function()
     let g:NUM_LVLS = 4
     function Redraw()
       mode
-      return ''
+      return "\<Ignore>"
     endfunction
     let g:id = ''
     cnoremap <expr> {REDRAW} Redraw()
@@ -42,7 +42,7 @@ before_each(function()
       let Cb = g:Nvim_color_input{g:id}
       let out = input({'prompt': ':', 'highlight': Cb})
       let g:out{id} = out
-      return (a:do_return ? out : '')
+      return (a:do_return ? out : "\<Ignore>")
     endfunction
     nnoremap <expr> {PROMPT} DoPrompt(0)
     cnoremap <expr> {PROMPT} DoPrompt(1)
@@ -410,7 +410,7 @@ describe('Command-line coloring', function()
   end)
   it('stops executing callback after a number of errors', function()
     set_color_cb('SplittedMultibyteStart')
-    start_prompt('let x = "«»«»«»«»«»"\n')
+    start_prompt('let x = "«»«»«»«»«»"')
     screen:expect([[
       {EOB:~                                       }|
       {EOB:~                                       }|
@@ -419,7 +419,7 @@ describe('Command-line coloring', function()
       :let x = "                              |
       {ERR:E5405: Chunk 0 start 10 splits multibyte}|
       {ERR: character}                              |
-      ^:let x = "«»«»«»«»«»"                   |
+      :let x = "«»«»«»«»«»"^                   |
     ]])
     feed('\n')
     screen:expect([[
@@ -432,6 +432,7 @@ describe('Command-line coloring', function()
       {EOB:~                                       }|
                                               |
     ]])
+    feed('\n')
     eq('let x = "«»«»«»«»«»"', meths.get_var('out'))
     local msg = '\nE5405: Chunk 0 start 10 splits multibyte character'
     eq(msg:rep(1), funcs.execute('messages'))
@@ -474,14 +475,14 @@ describe('Command-line coloring', function()
     ]])
     feed('\n')
     screen:expect([[
-                                              |
+      ^                                        |
       {EOB:~                                       }|
       {EOB:~                                       }|
       {EOB:~                                       }|
       {EOB:~                                       }|
       {EOB:~                                       }|
       {EOB:~                                       }|
-      ^:echo 42                                |
+      :echo 42                                |
     ]])
     feed('\n')
     eq('echo 42', meths.get_var('out'))