Handle multiple files localtion lists with gcc handler (#1034)

Handle multiple files in the GCC handler.

autoload/ale/handlers/gcc.vim

@@ -43,6 +43,10 @@ endfunction
 
 function! ale#handlers#gcc#HandleGCCFormat(buffer, lines) abort
     let l:include_pattern = '\v^(In file included | *)from ([^:]*):(\d+)'
+    " Include pattern looks for lines like :
+    "
+    " In file included from test.h:1:0,
+    "                  from test.cpp:1:
     let l:include_lnum = 0
     let l:include_lines = []
     let l:included_filename = ''
@@ -58,51 +62,42 @@ function! ale#handlers#gcc#HandleGCCFormat(buffer, lines) abort
         let l:match = matchlist(l:line, l:pattern)
 
         if empty(l:match)
-            " Check for matches in includes.
-            " We will keep matching lines until we hit the last file, which
-            " is our file.
             let l:include_match = matchlist(l:line, l:include_pattern)
-
-            if empty(l:include_match)
-                " If this isn't another include header line, then we
-                " need to collect it.
-                call add(l:include_lines, l:line)
-            else
-                " GCC and clang return the lists of files in different orders,
-                " so we'll only grab the line number from lines which aren't
-                " header files.
-                if !s:IsHeaderFile(l:include_match[2])
-                    " Get the line number out of the parsed include line,
-                    " and reset the other variables.
-                    let l:include_lnum = str2nr(l:include_match[3])
-                endif
-
-                let l:include_lines = []
-                let l:included_filename = ''
+            " If the line has an 'included from' pattern, store the line to
+            " create a gutter sign at the appropriate location in linted file
+            if !empty(l:include_match)
+                " We don't check if l:include_match[2] is linted filename
+                " because the last line matching include_pattern in a group
+                " of contiguous lines is probably concerning the linted file
+                " anyway
+                let l:include_lnum = l:include_match[3]
             endif
-        elseif l:include_lnum > 0
-        \&& (empty(l:included_filename) || l:included_filename is# l:match[1])
-            " If we hit the first error after an include header, or the
-            " errors below have the same name as the first filename we see,
-            " then include these lines, and remember what that filename was.
-            let l:included_filename = l:match[1]
-            call add(l:include_lines, l:line)
         else
-            " If we hit a regular error again, then add the previously
-            " collected lines as one error, and reset the include variables.
-            call s:AddIncludedErrors(l:output, l:include_lnum, l:include_lines)
-            let l:include_lnum = 0
-            let l:include_lines = []
-            let l:included_filename = ''
-
+            " Filter out the pragma errors
             if s:IsHeaderFile(bufname(bufnr('')))
             \&& l:match[5][:len(s:pragma_error) - 1] is# s:pragma_error
                 continue
             endif
 
+            " If the 'error type' is a note, make it detail related to
+            " the previous error parsed in output
+            if l:match[4] is# 'note'
+                let l:output[-1]['detail'] = get(l:output[-1], 'detail', '')
+                            \    . s:RemoveUnicodeQuotes(l:match[0]) . "\n"
+                continue
+            endif
+
+            " If l:include_lnum is non-null, then the error relates to
+            " an included file and l:include_lnum is the line number
+            " where a gutter sign would be needed in linted file
+
+            " The ternary operator in filename filters out the 'dummy'
+            " filenames like <nopath> or <stdin> and leave the location
+            " handling to engine#FixLocList
             let l:item = {
+            \   'filename': (l:match[1][:0] is# '<') ? '' : l:match[1],
             \   'lnum': str2nr(l:match[2]),
-            \   'type': l:match[4] =~# 'error' ? 'E' : 'W',
+            \   'type': l:match[4] is# 'error' ? 'E' : 'W',
             \   'text': s:RemoveUnicodeQuotes(l:match[5]),
             \}
 
@@ -110,12 +105,17 @@ function! ale#handlers#gcc#HandleGCCFormat(buffer, lines) abort
                 let l:item.col = str2nr(l:match[3])
             endif
 
+            " Finish filtering out filename : if the key exists but is empty,
+            " unlet it.
+            if get(l:item, 'filename', 'dummy_no_key_to_unlet') is# ''
+                unlet l:item['filename']
+            endif
+
             call add(l:output, l:item)
+            " Reset include_lnum after an error has been added
+            let l:include_lnum = 0
         endif
     endfor
 
-    " Add remaining include errors after we go beyond the last line.
-    call s:AddIncludedErrors(l:output, l:include_lnum, l:include_lines)
-
     return l:output
 endfunction