#2132 - lint and fix with ale#command#Run

A new function is added here which will later be modified for public use
in linter and fixer callbacks. All linting and fixing now goes through
this new function, to prove that it works in all cases.

autoload/ale/lsp_linter.vim

@@ -292,8 +292,17 @@ function! ale#lsp_linter#CheckWithLSP(buffer, linter) abort
     endif
 
     if l:notified
-        if index(l:info.active_linter_list, a:linter.name) < 0
-            call add(l:info.active_linter_list, a:linter.name)
+        let l:found = 0
+
+        for l:other_linter in l:info.active_linter_list
+            if l:other_linter.name is# a:linter.name
+                let l:found = 1
+                break
+            endif
+        endfor
+
+        if !l:found
+            call add(l:info.active_linter_list, a:linter)
         endif
     endif