diagnostics: support sending ALE output to Neovim's diagnostics API (#4345)

Support replacing ALE's display of problems with sending problems to the Neovim diagnostics API.

:help g:ale_use_neovim_diagnostics_api

Co-authored-by: David Balatero <dbalatero@users.noreply.github.com>
Co-authored-by: Georgi Angelchev <angelchev@live.co.uk>
Co-authored-by: w0rp <devw0rp@gmail.com>

9 files changed, 137 insertions, 12 deletions

diff --git a/autoload/ale/debugging.vim b/autoload/ale/debugging.vim
index 31f3078c..c100d6e6 100644
--- a/autoload/ale/debugging.vim
+++ b/autoload/ale/debugging.vim
@@ -55,6 +55,7 @@ let s:global_variable_list = [
 \    'ale_sign_highlight_linenrs',
 \    'ale_statusline_format',
 \    'ale_type_map',
+\    'ale_use_neovim_diagnostics_api',
 \    'ale_use_global_executables',
 \    'ale_virtualtext_cursor',
 \    'ale_warn_about_trailing_blank_lines',
diff --git a/autoload/ale/engine.vim b/autoload/ale/engine.vim
index 150bbc82..185d54db 100644
--- a/autoload/ale/engine.vim
+++ b/autoload/ale/engine.vim
@@ -184,9 +184,13 @@ endfunction
 function! ale#engine#SetResults(buffer, loclist) abort
     let l:linting_is_done = !ale#engine#IsCheckingBuffer(a:buffer)
 
+    if g:ale_use_neovim_diagnostics_api
+        call ale#engine#SendResultsToNeovimDiagnostics(a:buffer, a:loclist)
+    endif
+
     " Set signs first. This could potentially fix some line numbers.
     " The List could be sorted again here by SetSigns.
-    if g:ale_set_signs
+    if !g:ale_use_neovim_diagnostics_api && g:ale_set_signs
         call ale#sign#SetSigns(a:buffer, a:loclist)
     endif
 
@@ -199,11 +203,12 @@ function! ale#engine#SetResults(buffer, loclist) abort
         call ale#statusline#Update(a:buffer, a:loclist)
     endif
 
-    if g:ale_set_highlights
+    if !g:ale_use_neovim_diagnostics_api && g:ale_set_highlights
         call ale#highlight#SetHighlights(a:buffer, a:loclist)
     endif
 
-    if g:ale_virtualtext_cursor is# 'all' || g:ale_virtualtext_cursor == 2
+    if !g:ale_use_neovim_diagnostics_api
+    \&& (g:ale_virtualtext_cursor is# 'all' || g:ale_virtualtext_cursor == 2)
         call ale#virtualtext#SetTexts(a:buffer, a:loclist)
     endif
 
@@ -214,7 +219,8 @@ function! ale#engine#SetResults(buffer, loclist) abort
             call ale#cursor#EchoCursorWarning()
         endif
 
-        if g:ale_virtualtext_cursor is# 'current' || g:ale_virtualtext_cursor == 1
+        if !g:ale_use_neovim_diagnostics_api
+        \&& (g:ale_virtualtext_cursor is# 'current' || g:ale_virtualtext_cursor == 1)
             " Try and show the warning now.
             " This will only do something meaningful if we're in normal mode.
             call ale#virtualtext#ShowCursorWarning()
@@ -238,6 +244,19 @@ function! ale#engine#SetResults(buffer, loclist) abort
     endif
 endfunction
 
+function! ale#engine#SendResultsToNeovimDiagnostics(buffer, loclist) abort
+    if !has('nvim-0.6')
+        " We will warn the user on startup as well if they try to set
+        " g:ale_use_neovim_diagnostics_api outside of a Neovim context.
+        return
+    endif
+
+    " Keep the Lua surface area really small in the VimL part of ALE,
+    " and just require the diagnostics.lua module on demand.
+    let l:SendDiagnostics = luaeval('require("diagnostics").sendAleResultsToDiagnostics')
+    call l:SendDiagnostics(a:buffer, a:loclist)
+endfunction
+
 function! s:RemapItemTypes(type_map, loclist) abort
     for l:item in a:loclist
         let l:key = l:item.type
diff --git a/autoload/ale/virtualtext.vim b/autoload/ale/virtualtext.vim
index 0f2b2173..4897154b 100644
--- a/autoload/ale/virtualtext.vim
+++ b/autoload/ale/virtualtext.vim
@@ -187,10 +187,8 @@ function! ale#virtualtext#ShowCursorWarning(...) abort
     let l:buffer = bufnr('')
 
     if mode(1) isnot# 'n'
-        return
-    endif
-
-    if ale#ShouldDoNothing(l:buffer)
+    \|| g:ale_use_neovim_diagnostics_api
+    \|| ale#ShouldDoNothing(l:buffer)
         return
     endif
 
@@ -210,12 +208,13 @@ function! ale#virtualtext#ShowCursorWarningWithDelay() abort
         return
     endif
 
+    call s:StopCursorTimer()
+
     if mode(1) isnot# 'n'
+    \|| g:ale_use_neovim_diagnostics_api
         return
     endif
 
-    call s:StopCursorTimer()
-
     let l:pos = getpos('.')[0:2]
 
     " Check the current buffer, line, and column number against the last
diff --git a/doc/ale.txt b/doc/ale.txt
index 2876b235..c9bebd05 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -121,6 +121,7 @@ circumstances.
 ALE will report problems with your code in the following ways, listed with
 their relevant options.
 
+* Via the Neovim diagnostics API (Off by default)  - |g:ale_use_neovim_diagnostics_api|
 * By updating loclist. (On by default)             - |g:ale_set_loclist|
 * By updating quickfix. (Off by default)           - |g:ale_set_quickfix|
 * By setting error highlights.                     - |g:ale_set_highlights|
@@ -1235,7 +1236,7 @@ g:ale_floating_preview                                 *g:ale_floating_preview*
   |g:ale_detail_to_floating_preview| to `1`.
 
 
-g:ale_floating_preview_popup_opts             *g:ale_floating_preview_popup_opts*
+g:ale_floating_preview_popup_opts           *g:ale_floating_preview_popup_opts*
 
   Type: |String| or |Dictionary|
   Default: `''`
@@ -1258,7 +1259,7 @@ g:ale_floating_preview_popup_opts             *g:ale_floating_preview_popup_opts
 <
 
 
-g:ale_floating_window_border                       *g:ale_floating_window_border*
+g:ale_floating_window_border                     *g:ale_floating_window_border*
 
   Type: |List|
   Default: `['|', '-', '+', '+', '+', '+', '|', '-']`
@@ -2288,6 +2289,26 @@ g:ale_use_global_executables                     *g:ale_use_global_executables*
   options.
 
 
+g:ale_use_neovim_diagnostics_api             *g:ale_use_neovim_diagnostics_api*
+
+  Type: |Number|
+  Default: `0`
+
+  If enabled, this option will disable ALE's standard UI, and instead send
+  all linter output to Neovim's diagnostics API. This allows you to collect
+  errors from nvim-lsp, ALE, and anything else that uses diagnostics all in
+  one place. The following options are ignored when using the diagnostics API:
+
+    - |g:ale_set_highlights|
+    - |g:ale_set_signs|
+    - |g:ale_virtualtext_cursor|
+
+  To enable this option, set the value to `1`.
+
+  This option requires Neovim 0.6+, as that version introduces the diagnostics
+  API.
+
+
 g:ale_virtualtext_cursor                             *g:ale_virtualtext_cursor*
 
   Type: |Number|
diff --git a/lua/diagnostics.lua b/lua/diagnostics.lua
new file mode 100644
index 00000000..1ac6eb57
--- /dev/null
+++ b/lua/diagnostics.lua
@@ -0,0 +1,49 @@
+local module = {}
+
+local ale_type_to_diagnostic_severity = {
+  E = vim.diagnostic.severity.ERROR,
+  W = vim.diagnostic.severity.WARN,
+  I = vim.diagnostic.severity.INFO
+}
+
+module.sendAleResultsToDiagnostics = function(buffer, loclist)
+  local diagnostics = {}
+
+  -- Convert all the ALE loclist items to the shape that Neovim's diagnostic
+  -- API is expecting.
+  for _, location in ipairs(loclist) do
+    table.insert(
+      diagnostics,
+      -- All line numbers from ALE are 1-indexed, but all line numbers
+      -- in the diagnostics API are 0-indexed, so we have to subtract 1
+      -- to make this work.
+      {
+        lnum = location.lnum - 1,
+        -- Ending line number, or if we don't have one, just make it the same
+        -- as the starting line number
+        end_lnum = (location.end_lnum or location.lnum) - 1,
+        -- Which column does the error start on?
+        col = math.max((location.col or 1) - 1, 0),
+        -- end_col does *not* appear to need 1 subtracted, so we don't.
+        end_col = location.end_col,
+        -- Which severity: error, warning, or info?
+        severity = ale_type_to_diagnostic_severity[location.type] or "E",
+        -- The error message
+        message = location.text,
+        -- e.g. "rubocop"
+        source = location.linter_name,
+      }
+    )
+  end
+
+  local virtualtext_enabled_set = {['all'] = true, ['2'] = true, ['current'] = true, ['1'] = true}
+
+  vim.diagnostic.set(
+    vim.api.nvim_create_namespace('ale'),
+    buffer,
+    diagnostics,
+    { virtual_text = virtualtext_enabled_set[vim.g.ale_virtualtext_cursor] ~= nil}
+  )
+end
+
+return module
diff --git a/plugin/ale.vim b/plugin/ale.vim
index 6aa115ea..b9786bb0 100644
--- a/plugin/ale.vim
+++ b/plugin/ale.vim
@@ -187,6 +187,15 @@ let g:ale_deno_executable = get(g:, 'ale_deno_executable', 'deno')
 " If 1, enable a popup menu for commands.
 let g:ale_popup_menu_enabled = get(g:, 'ale_popup_menu_enabled', has('gui_running'))
 
+" If 1, disables ALE's built in error display. Instead, all errors are piped
+" to the diagnostics API.
+let g:ale_use_neovim_diagnostics_api = get(g:, 'ale_use_neovim_diagnostics_api', 0)
+
+if g:ale_use_neovim_diagnostics_api && !has('nvim-0.6')
+    " no-custom-checks
+    echoerr('Setting g:ale_use_neovim_diagnostics_api to 1 requires Neovim 0.6+.')
+endif
+
 if g:ale_set_balloons is 1 || g:ale_set_balloons is# 'hover'
     call ale#balloon#Enable()
 endif
diff --git a/test/sign/test_linting_sets_signs.vader b/test/sign/test_linting_sets_signs.vader
index 1624449a..6c1ac39f 100644
--- a/test/sign/test_linting_sets_signs.vader
+++ b/test/sign/test_linting_sets_signs.vader
@@ -11,6 +11,7 @@ Before:
   Save g:ale_set_quickfix
   Save g:ale_set_signs
   Save g:ale_command_wrapper
+  Save g:ale_use_neovim_diagnostics_api
 
   let g:ale_command_wrapper = ''
   let g:ale_buffer_info = {}
@@ -22,6 +23,7 @@ Before:
   let g:ale_set_loclist = 0
   let g:ale_set_highlights = 0
   let g:ale_echo_cursor = 0
+  let g:ale_use_neovim_diagnostics_api = 0
 
   call ale#sign#Clear()
 
@@ -74,3 +76,10 @@ Execute(The signs should be updated after linting is done):
   call ale#test#FlushJobs()
 
   AssertEqual [['1', 'ALEWarningSign'], ['2', 'ALEErrorSign']], CollectSigns()
+
+Execute(Signs should not be set when diagnostics API integration is enabled):
+  let g:ale_use_neovim_diagnostics_api = 1
+  ALELint
+  call ale#test#FlushJobs()
+
+  AssertEqual [], CollectSigns()
diff --git a/test/test_ale_info.vader b/test/test_ale_info.vader
index ded65a1f..4cedccc2 100644
--- a/test/test_ale_info.vader
+++ b/test/test_ale_info.vader
@@ -52,6 +52,7 @@ Before:
   Save g:ale_sign_highlight_linenrs
   Save g:ale_statusline_format
   Save g:ale_type_map
+  Save g:ale_use_neovim_diagnostics_api
   Save g:ale_use_global_executables
   Save g:ale_virtualtext_cursor
   Save g:ale_warn_about_trailing_blank_lines
@@ -110,6 +111,7 @@ Before:
   let g:ale_sign_highlight_linenrs = 0
   let g:ale_statusline_format = ['%d error(s)', '%d warning(s)', 'OK']
   let g:ale_type_map = {}
+  let g:ale_use_neovim_diagnostics_api = 0
   let g:ale_use_global_executables = v:null
   let g:ale_virtualtext_cursor = 'disabled'
   let g:ale_warn_about_trailing_blank_lines = 1
@@ -189,6 +191,7 @@ Before:
   \  'let g:ale_sign_highlight_linenrs = 0',
   \  'let g:ale_statusline_format = [''%d error(s)'', ''%d warning(s)'', ''OK'']',
   \  'let g:ale_type_map = {}',
+  \  'let g:ale_use_neovim_diagnostics_api = 0',
   \  'let g:ale_use_global_executables = v:null',
   \  'let g:ale_virtualtext_cursor = ''disabled''',
   \  'let g:ale_warn_about_trailing_blank_lines = 1',
diff --git a/test/test_virtualtext.vader b/test/test_virtualtext.vader
index 8fc1ead5..1d34c036 100644
--- a/test/test_virtualtext.vader
+++ b/test/test_virtualtext.vader
@@ -4,6 +4,7 @@ Before:
   Save g:ale_virtualtext_delay
   Save g:ale_virtualtext_prefix
   Save b:ale_virtualtext_prefix
+  Save g:ale_use_neovim_diagnostics_api
 
   call ale#virtualtext#ResetDataForTests()
 
@@ -36,6 +37,7 @@ Before:
   \   ],
   \ },
   \}
+  let g:ale_use_neovim_diagnostics_api = 0
 
 After:
   Restore
@@ -177,3 +179,16 @@ Execute(We should set errors across all lines):
       \ map(prop_list(2), {_, v -> v.type})
     endif
   endif
+
+Execute(We should not set cursor messages when Neovim diagnostics are enabled):
+  let g:ale_use_neovim_diagnostics_api = 1
+
+  if has('patch-9.0.0297') || has('nvim-0.8.0')
+    let g:ale_virtualtext_cursor = 'current'
+    call cursor(1, 1)
+    call ale#virtualtext#ShowCursorWarningWithDelay()
+    " Tick the timer.
+    sleep 1ms
+
+    AssertEqual '', ale#virtualtext#GetLastMessageForTests()
+  endif