Support older checkstyle versions

The output format used by older checkstyle versions differs from the one
of new versions. This commit adds a second parsing iteration on the
output lines with a suitable pattern to support both versions in
parallel. Due to the differences in the order of matching groups this is
hard to achieve in a single pass through the output lines.

An appropriate test case is added.

1 files changed, 14 insertions, 1 deletions

diff --git a/ale_linters/java/checkstyle.vim b/ale_linters/java/checkstyle.vim
index 8155170a..7d0c31ba 100644
--- a/ale_linters/java/checkstyle.vim
+++ b/ale_linters/java/checkstyle.vim
@@ -2,9 +2,11 @@
 " Description: checkstyle for Java files
 
 function! ale_linters#java#checkstyle#Handle(buffer, lines) abort
-    let l:pattern = '\v\[(WARN|ERROR)\] [a-zA-Z]?:?[^:]+:(\d+):(\d+)?:? (.*) \[(.+)\]$'
     let l:output = []
 
+    " modern checkstyle versions
+    let l:pattern = '\v\[(WARN|ERROR)\] [a-zA-Z]?:?[^:]+:(\d+):(\d+)?:? (.*) \[(.+)\]$'
+
     for l:match in ale#util#GetMatches(a:lines, l:pattern)
         call add(l:output, {
         \   'type': l:match[1] is? 'WARN' ? 'W' : 'E',
@@ -15,6 +17,17 @@ function! ale_linters#java#checkstyle#Handle(buffer, lines) abort
         \})
     endfor
 
+    " old checkstyle versions
+    let l:pattern = '\v(.+):(\d+): ([^:]+): (.+)$'
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'type': l:match[3] is? 'warning' ? 'W' : 'E',
+        \   'lnum': l:match[2] + 0,
+        \   'text': l:match[4],
+        \})
+    endfor
+
     return l:output
 endfunction