Fix #502 - Report undefined symbol errors better for javac

ale_linters/java/javac.vim

@@ -85,15 +85,23 @@ function! ale_linters#java#javac#Handle(buffer, lines) abort
     " Main.java:13: warning: [deprecation] donaught() in Testclass has been deprecated
     " Main.java:16: error: ';' expected
 
-    let l:pattern = '^.*\:\(\d\+\):\ \(.*\):\(.*\)$'
+    let l:pattern = '\v^.*:(\d+): (.+):(.+)$'
+    let l:symbol_pattern = '\v^ +symbol: *(class) +([^ ]+)'
     let l:output = []
 
-    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+    for l:match in ale#util#GetMatches(a:lines, [l:pattern, l:symbol_pattern])
+        if empty(l:match[3])
+            " Add symbols to 'cannot find symbol' errors.
+            if l:output[-1].text ==# 'error: cannot find symbol'
+                let l:output[-1].text .= ': ' . l:match[2]
+            endif
+        else
             call add(l:output, {
             \   'lnum': l:match[1] + 0,
             \   'text': l:match[2] . ':' . l:match[3],
             \   'type': l:match[2] ==# 'error' ? 'E' : 'W',
             \})
+        endif
     endfor
 
     return l:output

test/handler/test_javac_handler.vader

@@ -0,0 +1,45 @@
+Before:
+  runtime ale_linters/java/javac.vim
+
+After:
+  call ale#linter#Reset()
+
+Execute(The javac handler should handle cannot find symbol errors):
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 1,
+  \     'text': 'error: some error',
+  \     'type': 'E',
+  \   },
+  \   {
+  \     'lnum': 2,
+  \     'text': 'error: cannot find symbol: BadName',
+  \     'type': 'E',
+  \   },
+  \   {
+  \     'lnum': 34,
+  \     'text': 'error: cannot find symbol: BadName2',
+  \     'type': 'E',
+  \   },
+  \   {
+  \     'lnum': 37,
+  \     'text': 'warning: some warning',
+  \     'type': 'W',
+  \   },
+  \ ],
+  \ ale_linters#java#javac#Handle(347, [
+  \   '/tmp/vLPr4Q5/33/foo.java:1: error: some error',
+  \   '/tmp/vLPr4Q5/33/foo.java:2: error: cannot find symbol',
+  \   '    BadName foo() {',
+  \   '    ^',
+  \   '  symbol:   class BadName',
+  \   '  location: class Bar',
+  \   '/tmp/vLPr4Q5/33/foo.java:34: error: cannot find symbol',
+  \   '    BadName2 foo() {',
+  \   '    ^',
+  \   '  symbol:   class BadName2',
+  \   '  location: class Bar',
+  \   '/tmp/vLPr4Q5/33/foo.java:37: warning: some warning',
+  \   '4 errors',
+  \ ])