The checkstyle handler is capable of parsing the new and old output
formats. Unfortunately there are some particular output messages that
matched both the new and old regular expressions:
[WARN] whatever:11:7: WhitespaceAround: ''if'' is not followed by whitespace. [WhitespaceAround]
This caused ALE to report extra errors since the message was being
matched twice, once as a warning and another (incorrect) old formatted
error.
This MR fixes this by stopping any parsing using the old format regexp
is any errors of the new format are correcly parsed. There is no reason
to expect checkstyle to output both styles in the same report.
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.
