Fix #371 Allow ALE to be disabled in different buffers

test/test_disabling_ale.vader

@@ -0,0 +1,92 @@
+Before:
+  Save g:ale_buffer_info, g:ale_enabled, b:ale_enabled
+
+  function! TestCallback(buffer, output)
+    return []
+  endfunction
+
+  call ale#linter#Define('foobar', {
+  \ 'name': 'testlinter',
+  \ 'callback': 'TestCallback',
+  \ 'executable': 'echo',
+  \ 'command': 'true',
+  \})
+
+  function GetLastMessage()
+    redir => l:output
+      silent mess
+    redir END
+
+    let l:lines = split(l:output, "\n")
+
+    return empty(l:lines) ? '' : l:lines[-1]
+  endfunction
+
+  echomsg ''
+
+After:
+  Restore
+  call ale#linter#Reset()
+  delfunction TestCallback
+  delfunction GetLastMessage
+
+Given foobar (Some imaginary filetype):
+  foo
+  bar
+  baz
+
+Execute(Linting shouldn't happen when ALE is disabled globally):
+  let g:ale_enabled = 0
+  let g:ale_buffer_info = {}
+
+  call ale#Queue(0)
+
+  AssertEqual {}, g:ale_buffer_info
+
+Execute(Linting shouldn't happen when ALE is disabled locally):
+  let b:ale_enabled = 0
+  let g:ale_buffer_info = {}
+
+  call ale#Queue(0)
+
+  AssertEqual {}, g:ale_buffer_info
+
+Execute(Cursor warnings shouldn't be echoed when ALE is disabled globally):
+  let g:ale_enabled = 0
+  let g:ale_buffer_info = {
+  \ bufnr('%'): {
+  \   'loclist': [
+  \     {
+  \       'lnum': 2,
+  \       'col': 10,
+  \       'linter_name': 'testlinter',
+  \       'type': 'W',
+  \       'text': 'X'
+  \     },
+  \   ],
+  \ },
+  \}
+
+  call cursor(2, 16)
+  call ale#cursor#EchoCursorWarning()
+  AssertEqual '', GetLastMessage()
+
+Execute(Cursor warnings shouldn't be echoed when ALE is disabled locally):
+  let b:ale_enabled = 0
+  let g:ale_buffer_info = {
+  \ bufnr('%'): {
+  \   'loclist': [
+  \     {
+  \       'lnum': 2,
+  \       'col': 10,
+  \       'linter_name': 'testlinter',
+  \       'type': 'W',
+  \       'text': 'X'
+  \     },
+  \   ],
+  \ },
+  \}
+
+  call cursor(2, 16)
+  call ale#cursor#EchoCursorWarning()
+  AssertEqual '', GetLastMessage()