#965 - Support limiting the number of signs ALE will set

autoload/ale/sign.vim

@@ -209,7 +209,17 @@ function! s:UpdateLineNumbers(buffer, current_sign_list, loclist) abort
     endif
 endfunction
 
-function! s:BuildSignMap(current_sign_list, grouped_items) abort
+function! s:BuildSignMap(buffer, current_sign_list, grouped_items) abort
+    let l:max_signs = ale#Var(a:buffer, 'max_signs')
+
+    if l:max_signs is 0
+        let l:selected_grouped_items = []
+    elseif type(l:max_signs) is type(0) && l:max_signs > 0
+        let l:selected_grouped_items = a:grouped_items[:l:max_signs - 1]
+    else
+        let l:selected_grouped_items = a:grouped_items
+    endif
+
     let l:sign_map = {}
     let l:sign_offset = g:ale_sign_offset
 
@@ -235,7 +245,7 @@ function! s:BuildSignMap(current_sign_list, grouped_items) abort
         let l:sign_map[l:line] = l:sign_info
     endfor
 
-    for l:group in a:grouped_items
+    for l:group in l:selected_grouped_items
         let l:line = l:group[0].lnum
         let l:sign_info = get(l:sign_map, l:line, {
         \   'current_id_list': [],
@@ -346,7 +356,11 @@ function! ale#sign#SetSigns(buffer, loclist) abort
     let l:grouped_items = s:GroupLoclistItems(a:buffer, a:loclist)
 
     " Build a map of current and new signs, with the lines as the keys.
-    let l:sign_map = s:BuildSignMap(l:current_sign_list, l:grouped_items)
+    let l:sign_map = s:BuildSignMap(
+    \   a:buffer,
+    \   l:current_sign_list,
+    \   l:grouped_items,
+    \)
 
     let l:command_list = ale#sign#GetSignCommands(
     \   a:buffer,

doc/ale.txt

@@ -859,6 +859,23 @@ g:ale_max_buffer_history_size                   *g:ale_max_buffer_history_size*
   History can be disabled completely with |g:ale_history_enabled|.
 
 
+g:ale_max_signs                                               *g:ale_max_signs*
+                                                              *b:ale_max_signs*
+  Type: |Number|
+  Default: `-1`
+
+  When set to any positive integer, ALE will not render any more than the
+  given number of signs for any one buffer.
+
+  When set to `0`, no signs will be set, but sign processing will still be
+  done, so existing signs can be removed.
+
+  When set to any other value, no limit will be imposed on the number of signs
+  set.
+
+  For disabling sign processing, see |g:ale_set_signs|.
+
+
 g:ale_maximum_file_size                               *g:ale_maximum_file_size*
                                                       *b:ale_maximum_file_size*
   Type: |Number|
@@ -1006,6 +1023,8 @@ g:ale_set_signs                                               *g:ale_set_signs*
   When multiple problems exist on the same line, the signs will take
   precedence in the order above, from highest to lowest.
 
+  To limit the number of signs ALE will set, see |g:ale_max_signs|.
+
 
 g:ale_sign_column_always                             *g:ale_sign_column_always*
 

plugin/ale.vim

@@ -118,6 +118,9 @@ call ale#Set('list_window_size', 10)
 " This flag can be set to 0 to disable setting signs.
 " This is enabled by default only if the 'signs' feature exists.
 let g:ale_set_signs = get(g:, 'ale_set_signs', has('signs'))
+" This flag can be set to some integer to control the maximum number of signs
+" that ALE will set.
+let g:ale_max_signs = get(g:, 'ale_max_signs', -1)
 
 " This flag can be set to 1 to enable changing the sign column colors when
 " there are errors.

test/sign/test_sign_limits.vader

@@ -0,0 +1,57 @@
+Before:
+  Save g:ale_max_signs
+
+  let g:ale_max_signs = -1
+
+  function! SetNProblems(sign_count)
+    let l:loclist = []
+    let l:range = range(1, a:sign_count)
+    call setline(1, l:range)
+
+    for l:index in l:range
+      call add(l:loclist, {
+      \ 'bufnr': bufnr(''),
+      \ 'lnum': l:index,
+      \ 'col': 1,
+      \ 'type': 'E',
+      \ 'text': 'a',
+      \})
+    endfor
+
+    call ale#sign#SetSigns(bufnr(''), l:loclist)
+
+    return sort(map(ale#sign#FindCurrentSigns(bufnr(''))[1], 'v:val[0]'), 'n')
+  endfunction
+
+After:
+  Restore
+
+  unlet! b:ale_max_signs
+
+  delfunction SetNProblems
+
+  sign unplace *
+
+Execute(There should be no limit on signs with negative numbers):
+  AssertEqual range(1, 42), SetNProblems(42)
+
+Execute(0 signs should be set when the max is 0):
+  let g:ale_max_signs = 0
+
+  AssertEqual [], SetNProblems(42)
+
+Execute(1 signs should be set when the max is 1):
+  let g:ale_max_signs = 1
+
+  AssertEqual [1], SetNProblems(42)
+
+Execute(10 signs should be set when the max is 10):
+  let g:ale_max_signs = 10
+
+  " We'll check that we set signs for the first 10 items, not other lines.
+  AssertEqual range(1, 10), SetNProblems(42)
+
+Execute(5 signs should be set when the max is 5 for the buffer):
+  let b:ale_max_signs = 5
+
+  AssertEqual range(1, 5), SetNProblems(42)