Fix #804 - Do not run scalac for sbt files

ale_linters/scala/scalac.vim

@@ -1,6 +1,26 @@
-" Author: Zoltan Kalmar - https://github.com/kalmiz
+" Author: Zoltan Kalmar - https://github.com/kalmiz,
+"         w0rp <devw0rp@gmail.com>
 " Description: Basic scala support using scalac
 
+function! ale_linters#scala#scalac#GetExecutable(buffer) abort
+    if index(split(getbufvar(a:buffer, '&filetype'), '\.'), 'sbt') >= 0
+        " Don't check sbt files with scalac.
+        return ''
+    endif
+
+    return 'scalac'
+endfunction
+
+function! ale_linters#scala#scalac#GetCommand(buffer) abort
+    let l:executable = ale_linters#scala#scalac#GetExecutable(a:buffer)
+
+    if empty(l:executable)
+        return ''
+    endif
+
+    return ale#Escape(l:executable) . ' -Ystop-after:parser %t'
+endfunction
+
 function! ale_linters#scala#scalac#Handle(buffer, lines) abort
     " Matches patterns line the following:
     "
@@ -38,8 +58,8 @@ endfunction
 
 call ale#linter#Define('scala', {
 \   'name': 'scalac',
-\   'executable': 'scalac',
-\   'output_stream': 'stderr',
-\   'command': 'scalac -Ystop-after:parser %t',
+\   'executable_callback': 'ale_linters#scala#scalac#GetExecutable',
+\   'command_callback': 'ale_linters#scala#scalac#GetCommand',
 \   'callback': 'ale_linters#scala#scalac#Handle',
+\   'output_stream': 'stderr',
 \})

test/handler/test_scalac_handler.vader

@@ -0,0 +1,18 @@
+Before:
+    runtime ale_linters/scala/scalac.vim
+
+After:
+    call ale#linter#Reset()
+
+Given scala(An empty Scala file):
+
+Execute(The default executable and command should be correct):
+  AssertEqual 'scalac', ale_linters#scala#scalac#GetExecutable(bufnr(''))
+  AssertEqual
+  \ ale#Escape('scalac') . ' -Ystop-after:parser %t',
+  \ ale_linters#scala#scalac#GetCommand(bufnr(''))
+
+Given scala.sbt(An empty SBT file):
+Execute(scalac should not be run for sbt files):
+  AssertEqual '', ale_linters#scala#scalac#GetExecutable(bufnr(''))
+  AssertEqual '', ale_linters#scala#scalac#GetCommand(bufnr(''))