feat(completion): improve highlighting in info and signature windows

Details:
- Try using tree-sitter highlighting in both windows.
- Conceal characters in info window (might result in extra whitespace).

Resolve #1020
Resolve #1426

CHANGELOG.md

@@ -22,6 +22,9 @@
 ## mini.completion
 
 - FEATURE: respect `isIncomplete` in LSP completion response and immediately force new completion request on the next key press.
+- FEATURE: both info and signature help windows now use tree-sitter highlighting:
+    - Info window uses "markdown" parser (works best on Neovim>=0.10 as its parser is built-in). Special markdown characters are concealed (i.e. hidden) which might result into seemingly unnecessary whitespace as dimensions are computed not accounting for that.
+    - Signature help uses same parser as in current filetype.
 
 ## mini.doc
 

lua/mini/completion.lua

@@ -971,7 +971,7 @@ H.show_info_window = function()
     lines = H.process_lsp_response(H.info.lsp.result, function(response)
       if not response.documentation then return {} end
       local res = vim.lsp.util.convert_input_to_markdown_lines(response.documentation)
-      return H.normalize_lines(res)
+      return H.normalize_markdown_lines(res)
     end)
 
     H.info.lsp.status = 'done'
@@ -982,25 +982,25 @@ H.show_info_window = function()
   -- Don't show anything if there is nothing to show
   if not lines or H.is_whitespace(lines) then return end
 
-  -- If not already, create a permanent buffer where info will be
-  -- displayed. For some reason, it is important to have it created not in
-  -- `setup()` because in that case there is a small flash (which is really a
-  -- brief open of window at screen top, focus on it, and its close) on the
-  -- first show of info window.
+  -- Ensure permanent buffer with "markdown" highlighting to display info
   H.ensure_buffer(H.info, 'MiniCompletion:completion-item-info')
-
-  -- Add `lines` to info buffer. Use `wrap_at` to have proper width of
-  -- 'non-UTF8' section separators.
-  H.stylize_markdown(H.info.bufnr, lines, { wrap_at = H.get_config().window.info.width })
+  H.ensure_highlight(H.info, 'markdown')
+  vim.api.nvim_buf_set_lines(H.info.bufnr, 0, -1, false, lines)
 
   -- Compute floating window options
   local opts = H.info_window_options()
 
+  -- Adjust section separator with better visual alternative
+  lines = vim.tbl_map(function(l) return l:gsub('^%-%-%-%-*$', string.rep('─', opts.width)) end, lines)
+  vim.api.nvim_buf_set_lines(H.info.bufnr, 0, -1, false, lines)
+
   -- Defer execution because of textlock during `CompleteChanged` event
   vim.schedule(function()
     -- Ensure that window doesn't open when it shouldn't be
     if not (H.pumvisible() and vim.fn.mode() == 'i') then return end
     H.open_action_window(H.info, opts)
+    -- Hide helper syntax elements (like ``` code blocks, etc.)
+    vim.wo[H.info.win_id].conceallevel = 3
   end)
 end
 
@@ -1009,13 +1009,7 @@ H.info_window_lines = function(info_id)
   local completed_item = H.table_get(H.info, { 'event', 'completed_item' }) or {}
   local text = completed_item.info or ''
 
-  if not H.is_whitespace(text) then
-    -- Use `<text></text>` to be properly processed by `stylize_markdown()`
-    local lines = { '<text>' }
-    vim.list_extend(lines, vim.split(text, '\n'))
-    table.insert(lines, '</text>')
-    return lines
-  end
+  if not H.is_whitespace(text) then return vim.split(text, '\n') end
 
   -- If popup is not from LSP then there is nothing more to do
   if H.completion.source ~= 'lsp' then return nil end
@@ -1028,7 +1022,7 @@ H.info_window_lines = function(info_id)
   local doc = lsp_completion_item.documentation
   if doc then
     local lines = vim.lsp.util.convert_input_to_markdown_lines(doc)
-    return H.normalize_lines(lines)
+    return H.normalize_markdown_lines(lines)
   end
 
   -- Finally, try request to resolve current completion to add documentation
@@ -1136,19 +1130,13 @@ H.show_signature_window = function()
     return
   end
 
-  -- Make markdown code block
-  table.insert(lines, 1, '```' .. vim.bo.filetype)
-  table.insert(lines, '```')
-
-  -- If not already, create a permanent buffer for signature
+  -- Ensure permanent buffer with current highlighting to display signature
   H.ensure_buffer(H.signature, 'MiniCompletion:signature-help')
-
-  -- Add `lines` to signature buffer. Use `wrap_at` to have proper width of
-  -- 'non-UTF8' section separators.
-  local buf_id = H.signature.bufnr
-  H.stylize_markdown(buf_id, lines, { wrap_at = H.get_config().window.signature.width })
+  H.ensure_highlight(H.signature, vim.bo.filetype)
+  vim.api.nvim_buf_set_lines(H.signature.bufnr, 0, -1, false, lines)
 
   -- Add highlighting of active parameter
+  local buf_id = H.signature.bufnr
   for i, hl_range in ipairs(hl_ranges) do
     if not vim.tbl_isempty(hl_range) and hl_range.first and hl_range.last then
       local first, last = hl_range.first, hl_range.last
@@ -1285,21 +1273,35 @@ end
 
 -- Helpers for floating windows -----------------------------------------------
 H.ensure_buffer = function(cache, name)
-  if type(cache.bufnr) == 'number' and vim.api.nvim_buf_is_valid(cache.bufnr) then return end
+  if H.is_valid_buf(cache.bufnr) then return end
 
-  cache.bufnr = vim.api.nvim_create_buf(false, true)
-  vim.api.nvim_buf_set_name(cache.bufnr, name)
-  -- Make this buffer a scratch (can close without saving)
-  vim.fn.setbufvar(cache.bufnr, '&buftype', 'nofile')
+  local buf_id = vim.api.nvim_create_buf(false, true)
+  cache.bufnr = buf_id
+  vim.api.nvim_buf_set_name(buf_id, name)
+  vim.bo[buf_id].buftype = 'nofile'
+end
+
+H.ensure_highlight = function(cache, filetype)
+  if cache.hl_filetype == filetype then return end
+  cache.hl_filetype = filetype
+  local buf_id = cache.bufnr
+
+  local has_lang, lang = pcall(vim.treesitter.language.get_lang, filetype)
+  lang = has_lang and lang or filetype
+  -- TODO: Remove `opts.error` after compatibility with Neovim=0.11 is dropped
+  local has_parser, parser = pcall(vim.treesitter.get_parser, buf_id, lang, { error = false })
+  has_parser = has_parser and parser ~= nil
+  if has_parser then has_parser = pcall(vim.treesitter.start, buf_id, lang) end
+  if not has_parser then vim.bo[buf_id].syntax = filetype end
 end
 
 -- Returns tuple of height and width
 H.floating_dimensions = function(lines, max_height, max_width)
   max_height, max_width = math.max(max_height, 1), math.max(max_width, 1)
 
   -- Simulate how lines will look in window with `wrap` and `linebreak`.
-  -- This is not 100% accurate (mostly when multibyte characters are present
-  -- manifesting into empty space at bottom), but does the job
+  -- This is not 100% accurate (mostly because of concealed characters and
+  -- multibyte manifest into empty space at bottom), but does the job
   local lines_wrap = {}
   for _, l in pairs(lines) do
     vim.list_extend(lines_wrap, H.wrap_line(l, max_width))
@@ -1336,13 +1338,11 @@ end
 H.close_action_window = function(cache, keep_timer)
   if not keep_timer then cache.timer:stop() end
 
-  if type(cache.win_id) == 'number' and vim.api.nvim_win_is_valid(cache.win_id) then
-    vim.api.nvim_win_close(cache.win_id, true)
-  end
+  if H.is_valid_win(cache.win_id) then vim.api.nvim_win_close(cache.win_id, true) end
   cache.win_id = nil
 
   -- For some reason 'buftype' might be reset. Ensure that buffer is scratch.
-  if cache.bufnr then vim.fn.setbufvar(cache.bufnr, '&buftype', 'nofile') end
+  if H.is_valid_buf(cache.bufnr) then vim.bo[cache.bufnr].buftype = 'nofile' end
 end
 
 -- Utilities ------------------------------------------------------------------
@@ -1353,6 +1353,10 @@ H.check_type = function(name, val, ref, allow_nil)
   H.error(string.format('`%s` should be %s, not %s', name, ref, type(val)))
 end
 
+H.is_valid_buf = function(buf_id) return type(buf_id) == 'number' and vim.api.nvim_buf_is_valid(buf_id) end
+
+H.is_valid_win = function(win_id) return type(win_id) == 'number' and vim.api.nvim_win_is_valid(win_id) end
+
 H.is_char_keyword = function(char)
   -- Using Vim's `match()` and `keyword` enables respecting Cyrillic letters
   return vim.fn.match(char, '[[:keyword:]]') >= 0
@@ -1452,16 +1456,16 @@ H.map = function(mode, lhs, rhs, opts)
   vim.keymap.set(mode, lhs, rhs, opts)
 end
 
-H.normalize_lines = function(lines)
-  -- Enaure no newline characters and no leading/trailing empty lines
-  lines = table.concat(lines, '\n'):gsub('^\n+', ''):gsub('\n+$', '')
+H.normalize_markdown_lines = function(lines)
+  -- Remove trailing whitespace (converts blank lines to empty)
+  lines = table.concat(lines, '\n'):gsub('[ \t]+\n', '\n'):gsub('[ \t]+$', '\n')
+  -- Collapse multiple empty lines, remove top and bottom padding
+  lines = lines:gsub('\n\n+', '\n\n'):gsub('^\n+', ''):gsub('\n+$', '')
+  -- Remove padding around code blocks as they are concealed and appear empty
+  lines = lines:gsub('\n*(\n```%S+\n)', '%1'):gsub('(\n```\n?)\n*', '%1')
   return vim.split(lines, '\n')
 end
 
-H.stylize_markdown = function(buf_id, lines, opts)
-  return vim.lsp.util.stylize_markdown(buf_id, H.normalize_lines(lines), opts)
-end
-
 -- TODO: Remove after compatibility with Neovim=0.9 is dropped
 H.islist = vim.fn.has('nvim-0.10') == 1 and vim.islist or vim.tbl_islist
 

tests/dir-completion/mock-months-lsp.lua

@@ -16,14 +16,43 @@ Months.items = {
   { name = 'December',  kind = 1 },
 }
 
+local markdown_info = {
+  -- Should remove all blank lines from the top
+  '',
+  '  ',
+  '# Month #07',
+  -- Should collapse multiple blank lines into one
+  '',
+  ' ',
+  '\t',
+  -- Should replace section separator with continuous one spanning window width
+  '---',
+  '',
+  -- Should conceal special characters and highlight
+  'This *is* __markdown__ text',
+  '',
+  ' ',
+  -- Should conceal code block characters *and* remove all blank lines before
+  -- and after code block (as those will be displayed as empty themselves)
+  '```lua',
+  'local a = 1',
+  '```',
+  -- Should remove all blank lines from the bottom
+  ' ',
+  '',
+  '\t',
+  ' ',
+  '',
+}
+
 Months.data = {
   January   = { documentation = 'Month #01' },
   February  = { documentation = 'Month #02' },
   March     = { documentation = 'Month #03' },
   April     = { documentation = 'Month #04' },
   May       = { documentation = 'Month #05' },
   June      = { documentation = 'Month #06' },
-  July      = { documentation = 'Month #07' },
+  July      = { documentation = table.concat(markdown_info, '\n') },
   August    = { documentation = 'Month #08' },
   September = { documentation = 'Month #09' },
   October   = { documentation = 'Month #10' },
@@ -141,6 +170,8 @@ Months.requests = {
     local label, parameters
     if word == 'long(' then
       label = string.rep('a ', 1000)
+    elseif word == 'string.format(' then
+      label = 'function string.format(s:string|number, ...any)'
     else
       label = 'abc(param1, param2)'
       parameters = { { label = { 4, 10 } }, { label = { 12, 18 } } }

tests/screenshots/tests-test_completion.lua---Information-window---stylizes-markdown-with-concealed-characters

@@ -0,0 +1,33 @@
+--|---------|---------|---------|---------|-----
+01|July                                         
+02|July Function  # Month #07                   
+03|~                                            
+04|~              ───────────────────────────   
+05|~                                            
+06|~              This is markdown text         
+07|~                                            
+08|~              local a = 1                   
+09|~                                            
+10|~                                            
+11|~                                            
+12|~                                            
+13|~                                            
+14|[No Name] [+]              1,5            All
+15|-- INSERT --                                 
+
+--|---------|---------|---------|---------|-----
+01|000000000000000000000000000000000000000000000
+02|111111111111111222222222223333333333333333444
+03|444444444444444333333333333333333333333333444
+04|444444444444444333333333333333333333333333444
+05|444444444444444333333333333333333333333333444
+06|444444444444444333335536666666633333333333444
+07|444444444444444333333333333333333333333333444
+08|444444444444444666667373783333333333333333444
+09|444444444444444333333333333333333333333333444
+10|444444444444444444444444444444444444444444444
+11|444444444444444444444444444444444444444444444
+12|444444444444444444444444444444444444444444444
+13|444444444444444444444444444444444444444444444
+14|999999999999999999999999999999999999999999999
+15|::::::::::::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

tests/screenshots/tests-test_completion.lua---Signature-help---stylizes-markdown-with-concealed-characters

@@ -0,0 +1,23 @@
+--|---------|---------|---------|---------|---------|---------|-----
+01|string.format(                                                   
+02|~             function string.format(s:string|number, ...any)    
+03|~                                                                
+04|~                                                                
+05|~                                                                
+06|~                                                                
+07|~                                                                
+08|~                                                                
+09|[No Name] [+]                                  1,15           All
+10|-- INSERT --                                                     
+
+--|---------|---------|---------|---------|---------|---------|-----
+01|00000012222221333333333333333333333333333333333333333333333333333
+02|44444444444444555555555666666788888875766666659999997566655574444
+03|44444444444444444444444444444444444444444444444444444444444444444
+04|44444444444444444444444444444444444444444444444444444444444444444
+05|44444444444444444444444444444444444444444444444444444444444444444
+06|44444444444444444444444444444444444444444444444444444444444444444
+07|44444444444444444444444444444444444444444444444444444444444444444
+08|44444444444444444444444444444444444444444444444444444444444444444
+09|:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+10|;;;;;;;;;;;;<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

tests/test_completion.lua

@@ -873,6 +873,17 @@ T['Information window']['adjusts window width'] = function()
   child.expect_screenshot()
 end
 
+T['Information window']['stylizes markdown with concealed characters'] = function()
+  if child.fn.has('nvim-0.10') == 0 then MiniTest.skip('Screenshots are generated for Neovim>=0.10') end
+
+  child.set_size(15, 45)
+  type_keys('i', 'Jul', '<C-Space>')
+  type_keys('<C-n>')
+  eq(get_floating_windows(), {})
+  sleep(default_info_delay + small_time)
+  child.expect_screenshot()
+end
+
 T['Information window']['implements debounce-style delay'] = function()
   type_keys('i', 'J', '<C-Space>')
   eq(get_completion(), { 'January', 'June', 'July' })
@@ -1039,6 +1050,16 @@ T['Signature help']['adjusts window height'] = function()
   child.expect_screenshot()
 end
 
+T['Signature help']['stylizes markdown with concealed characters'] = function()
+  if child.fn.has('nvim-0.10') == 0 then MiniTest.skip('Screenshots are generated for Neovim>=0.10') end
+
+  child.set_size(10, 65)
+  child.bo.filetype = 'lua'
+  type_keys('i', 'string.format(')
+  sleep(default_signature_delay + small_time)
+  child.expect_screenshot()
+end
+
 T['Signature help']['implements debounce-style delay'] = function()
   child.cmd('startinsert')
   type_keys('abc(')