refactor(test): deprecate n.feed_command() #32915

Problem:
`feed_command()` was added as a "bridge" for old test code. 99% of those
cases should be using `n.command()`, which raises errors instead of
silently continuing the test.

Solution:
Deprecate `feed_command()`. It should not be used in new tests.
All usages of `feed_command()` should be converted to `command()` or
`feed()`.

runtime/doc/news.txt

@@ -70,12 +70,6 @@ BUILD
 • Translations are turned off by default. Enable by building Nvim with the
   CMake flag `ENABLE_TRANSLATIONS=ON`.
 
-DEFAULTS
-
-• 'number', 'relativenumber', 'signcolumn', and 'foldcolumn' are disabled in
-  |terminal| buffers. See |terminal-config| for an example of changing these defaults.
-• 'diffopt' default includes "linematch:40".
-
 DIAGNOSTICS
 
 • The "underline" diagnostics handler sorts diagnostics by severity when using
@@ -247,6 +241,11 @@ DEFAULTS
   • |[[| and |]]| in Normal mode jump between shell prompts for shells which emit
     OSC 133 sequences ("shell integration" or "semantic prompts").
 
+• Options:
+  • 'diffopt' default includes "linematch:40".
+  • 'number', 'relativenumber', 'signcolumn', and 'foldcolumn' are disabled in
+    |terminal| buffers. |terminal-config| shows how to change these defaults.
+
 • Snippet:
   • `<Tab>` in Insert and Select mode maps to `vim.snippet.jump({ direction = 1 })`
     when a snippet is active and jumpable forwards.

test/functional/editor/completion_spec.lua

@@ -4,8 +4,8 @@ local Screen = require('test.functional.ui.screen')
 
 local assert_alive = n.assert_alive
 local clear, feed = n.clear, n.feed
-local eval, eq, neq, ok = n.eval, t.eq, t.neq, t.ok
+local eval, eq, ok = n.eval, t.eq, t.ok
-local feed_command, source, expect = n.feed_command, n.source, n.expect
+local source, expect = n.source, n.expect
 local fn = n.fn
 local command = n.command
 local api = n.api
@@ -17,6 +17,11 @@ describe('completion', function()
 
   before_each(function()
     clear()
+    source([[
+      set completeopt-=noselect
+      " Avoid tags completion (if running test locally).
+      set complete-=t
+    ]])
     screen = Screen.new(60, 8)
     screen:add_extra_attr_ids {
       [100] = { foreground = Screen.colors.Gray0, background = Screen.colors.Yellow },
@@ -57,29 +62,12 @@ describe('completion', function()
     it('is readonly', function()
       screen:try_resize(80, 8)
       feed('ifoo<ESC>o<C-x><C-n><ESC>')
-      feed_command('let v:completed_item.word = "bar"')
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.word = "bar"'))
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.abbr = "bar"'))
-      feed_command('let v:errmsg = ""')
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.menu = "bar"'))
-
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.info = "bar"'))
-      feed_command('let v:completed_item.abbr = "bar"')
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.kind = "bar"'))
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
+      t.matches('E46%: ', t.pcall_err(command, 'let v:completed_item.user_data = "bar"'))
-      feed_command('let v:errmsg = ""')
-
-      feed_command('let v:completed_item.menu = "bar"')
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
-      feed_command('let v:errmsg = ""')
-
-      feed_command('let v:completed_item.info = "bar"')
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
-      feed_command('let v:errmsg = ""')
-
-      feed_command('let v:completed_item.kind = "bar"')
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
-      feed_command('let v:errmsg = ""')
-
-      feed_command('let v:completed_item.user_data = "bar"')
-      neq(nil, string.find(eval('v:errmsg'), '^E46: '))
-      feed_command('let v:errmsg = ""')
     end)
     it('returns expected dict in omni completion', function()
       source([[
@@ -122,7 +110,7 @@ describe('completion', function()
     end)
 
     it('inserts the first candidate if default', function()
-      feed_command('set completeopt+=menuone')
+      command('set completeopt+=menuone')
       feed('ifoo<ESC>o')
       screen:expect([[
         foo                                                         |
@@ -160,7 +148,7 @@ describe('completion', function()
       eq('foo', eval('getline(3)'))
     end)
     it('selects the first candidate if noinsert', function()
-      feed_command('set completeopt+=menuone,noinsert')
+      command('set completeopt+=menuone,noinsert')
       feed('ifoo<ESC>o<C-x><C-n>')
       screen:expect([[
         foo                                                         |
@@ -190,7 +178,7 @@ describe('completion', function()
       eq('foo', eval('getline(3)'))
     end)
     it('does not insert the first candidate if noselect', function()
-      feed_command('set completeopt+=menuone,noselect')
+      command('set completeopt+=menuone,noselect')
       feed('ifoo<ESC>o<C-x><C-n>')
       screen:expect([[
         foo                                                         |
@@ -221,7 +209,7 @@ describe('completion', function()
       eq('bar', eval('getline(3)'))
     end)
     it('does not select/insert the first candidate if noselect and noinsert', function()
-      feed_command('set completeopt+=menuone,noselect,noinsert')
+      command('set completeopt+=menuone,noselect,noinsert')
       feed('ifoo<ESC>o<C-x><C-n>')
       screen:expect([[
         foo                                                         |
@@ -258,14 +246,14 @@ describe('completion', function()
       eq('', eval('getline(3)'))
     end)
     it('does not change modified state if noinsert', function()
-      feed_command('set completeopt+=menuone,noinsert')
+      command('set completeopt+=menuone,noinsert')
-      feed_command('setlocal nomodified')
+      command('setlocal nomodified')
       feed('i<C-r>=TestComplete()<CR><ESC>')
       eq(0, eval('&l:modified'))
     end)
     it('does not change modified state if noselect', function()
-      feed_command('set completeopt+=menuone,noselect')
+      command('set completeopt+=menuone,noselect')
-      feed_command('setlocal nomodified')
+      command('setlocal nomodified')
       feed('i<C-r>=TestComplete()<CR><ESC>')
       eq(0, eval('&l:modified'))
     end)
@@ -279,8 +267,8 @@ describe('completion', function()
         return ''
       endfunction
       ]])
-      feed_command('set completeopt+=noselect,noinsert')
+      command('set completeopt+=noselect,noinsert')
-      feed_command('inoremap <right> <c-r>=TestComplete()<cr>')
+      command('inoremap <right> <c-r>=TestComplete()<cr>')
     end)
 
     local tests = {
@@ -534,7 +522,7 @@ describe('completion', function()
         return ''
       endfunction
       ]])
-      feed_command('set completeopt=menuone,noselect')
+      command('set completeopt=menuone,noselect')
     end)
 
     it('works', function()
@@ -792,7 +780,7 @@ describe('completion', function()
   end)
 
   it('disables folding during completion', function()
-    feed_command('set foldmethod=indent')
+    command('set foldmethod=indent')
     feed('i<Tab>foo<CR><Tab>bar<Esc>gg')
     screen:expect([[
               ^foo                                                 |
@@ -811,7 +799,7 @@ describe('completion', function()
   end)
 
   it('popupmenu is not interrupted by events', function()
-    feed_command('set complete=.')
+    command('set complete=.')
 
     feed('ifoobar fooegg<cr>f<c-p>')
     screen:expect([[
@@ -1027,8 +1015,8 @@ describe('completion', function()
   end)
 
   it("'ignorecase' 'infercase' CTRL-X CTRL-N #6451", function()
-    feed_command('set ignorecase infercase')
+    command('set ignorecase infercase')
-    feed_command('edit runtime/doc/credits.txt')
+    command('edit runtime/doc/credits.txt')
     feed('oX<C-X><C-N>')
     screen:expect {
       grid = [[

test/functional/testnvim.lua

@@ -620,6 +620,8 @@ function M.insert(...)
   nvim_feed('<ESC>')
 end
 
+--- @deprecated Use `command()` or `feed()` instead.
+---
 --- Executes an ex-command by user input. Because nvim_input() is used, Vimscript
 --- errors will not manifest as client (lua) errors. Use command() for that.
 --- @param ... string