Fix 368 - Lacheck reports errors from input{} files.

This PR adds additional check to lacheck linter to exclude any warnings
related to sourced files via latex \input{} command.

Closes: #368

ale_linters/tex/lacheck.vim

@@ -8,20 +8,26 @@ function! ale_linters#tex#lacheck#Handle(buffer, lines) abort
     "
     " "book.tex", line 37: possible unwanted space at "{"
     " "book.tex", line 38: missing `\ ' after "etc."
-    let l:pattern = '^".\+", line \(\d\+\): \(.\+\)$'
+    let l:pattern = '^"\(.\+\)", line \(\d\+\): \(.\+\)$'
     let l:output = []
 
     for l:match in ale#util#GetMatches(a:lines, l:pattern)
         " lacheck follows `\input{}` commands. If the cwd is not the same as the
         " file in the buffer then it will fail to find the inputed items. We do not
         " want warnings from those items anyway
-        if !empty(matchstr(l:match[2], '^Could not open ".\+"$'))
+        if !empty(matchstr(l:match[3], '^Could not open ".\+"$'))
+            continue
+        endif
+
+        " lacheck follows `\input{}` commands. We are only interested in
+        " reporting errors for the current buffer only.
+        if empty(matchstr(fnamemodify(l:match[1], ':t'), bufname(a:buffer)))
             continue
         endif
 
         call add(l:output, {
-        \   'lnum': l:match[1] + 0,
-        \   'text': l:match[2],
+        \   'lnum': l:match[2] + 0,
+        \   'text': l:match[3],
         \   'type': 'W',
         \})
     endfor