Implement buffer-wide virtual text support

[vimpostor]

This implements buffer-wide virtual text as detailed in #2962, both for vim and neovim.

You can activate it with let g:ale_virtualtext_cursor = 2.

Note that sometimes there is a problem, where very similar warnings appear
twice as virtual text, but this is not a bug in the implementation, rather it's
a problem of using multiple linters that return very similar warnings.

Demo

[hsanson]

Can verify this works in Neovim 0.7 and does not break anything as far as I can see. Again would be better if someone (not the PR author) can check this works fine in their environment using Vim.

[RyanSquared]

Error detected while processing function ale#virtualtext#ShowCursorWarning[17]..ale#virtualtext#Clear:
line   12:
E121: Undefined variable: s:hl_list
Error detected while processing function ale#virtualtext#ShowCursorWarning[17]..ale#virtualtext#Clear:
line   12:
E116: Invalid arguments for function empty(s:hl_list)

Using: VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Apr 18 2022 19:26:30)

[RyanSquared]

I believe this happens because s:hl_list is only set when s:emulate_virt is not set, but the following is run as a test: if s:emulate_virt && s:last_virt != -1. When opening a file, s:emulate_virt && s:last_virt != -1 is not true, so it goes to the second expression, which relies on s:hl_list. This can be fixed by checking !s:emulate_virt && !empty(s:hl_list), as it will skip the second half of the expression if the first half fails.

[RyanSquared]

This also completely breaks all virtualtext for Vim using emulated virtual text. I am unsure if the buffer-wide virtualtext should be supported or not, but I would prefer it to not break vim 8.x setups.

[vimpostor]

This also completely breaks all virtualtext for Vim using emulated virtual text. I am unsure if the buffer-wide virtualtext should be supported or not, but I would prefer it to not break vim 8.x setups.

Yeah, sorry I only tested with vim 9 and neovim, will fix that asap

I originally intended to remove the vim 8.2 compatibility virtual text, because it is a total hack and buggy on its own, but I guess we can leave it for now.
FYI buffer-wide virtual text will require vim 9 (or neovim)

[WhiteBlackGoose]

Again would be better if someone (not the PR author) can check this works fine in their environment using Vim.

Works fine! Thank you all, people who make it!

info:

NVIM v0.7.0
Build type: Release
LuaJIT 2.1.0-beta3
Compiled by runner@fv-az316-460

ALEInfo

 Current Filetype: cs
Available Linters: ['csc', 'cspell', 'mcs', 'mcsc']
  Enabled Linters: []
  Ignored Linters: []
 Suggested Fixers: 
  'dotnet-format' - Fix C# files with dotnet format.
  'remove_trailing_lines' - Remove all blank lines at the end of a file.
  'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
  'uncrustify' - Fix C, C++, C#, ObjectiveC, ObjectiveC++, D, Java, Pawn, and VALA files with uncrustify.
 Linter Variables:

 Global Variables:

let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = 0
let g:ale_command_wrapper = v:null
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = 0
let g:ale_completion_max_suggestions = v:null
let g:ale_disable_lsp = 0
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = '[%linter%] %s'
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'Warning'
let g:ale_enabled = 1
let g:ale_fix_on_save = 0
let g:ale_fixers = {}
let g:ale_history_enabled = 1
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_insert_leave = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {}
let b:ale_linters = ['code_checker']
let g:ale_linters_explicit = 0
let g:ale_linters_ignore = {}
let g:ale_list_vertical = 0
let g:ale_list_window_size = 10
let g:ale_loclist_msg_format = '[%linter%] %s'
let g:ale_max_buffer_history_size = v:null
let g:ale_max_signs = -1
let g:ale_maximum_file_size = v:null
let g:ale_open_list = 0
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_root = {}
let g:ale_set_balloons = 0
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = 0
let g:ale_sign_error = ' '
let g:ale_sign_info = ' '
let g:ale_sign_offset = 1000000
let g:ale_sign_style_error = ' '
let g:ale_sign_style_warning = ' '
let g:ale_sign_warning = ' '
let g:ale_sign_highlight_linenrs = 0
let g:ale_statusline_format = v:null
let g:ale_type_map = {}
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 2
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1
  Command History:

[jeffdn]

This works great for me:

ViM v9.0.350

[hsanson]

Thanks for the contribution and to those that verified it working.

[hsanson]

@vimpostor there is a merge conflict. Appreciated if you can take a look into it.

[vimpostor]

I fixed the merge conflict.

[WhiteBlackGoose]

Thanks!