LSP configuration via didChangeConfiguration (#1852)

* adding LSP configuration via workspace/didChangeConfiguration

test/lsp/test_lsp_client_messages.vader

@@ -175,6 +175,22 @@ Execute(ale#lsp#message#Hover() should return correct messages):
   \ ],
   \ ale#lsp#message#Hover(bufnr(''), 12, 34)
 
+Execute(ale#lsp#message#DidChangeConfiguration() should return correct messages):
+  let g:ale_lsp_configuration = {
+  \ 'foo': 'bar'
+  \ }
+  AssertEqual
+  \ [
+  \   0,
+  \   'workspace/didChangeConfiguration',
+  \   {
+  \     'settings': {
+  \         'foo': 'bar',
+  \     }
+  \   }
+  \ ],
+  \ ale#lsp#message#DidChangeConfiguration(bufnr(''), g:ale_lsp_configuration)
+
 Execute(ale#lsp#tsserver_message#Open() should return correct messages):
   AssertEqual
   \ [

test/test_linter_defintion_processing.vader

@@ -490,7 +490,7 @@ Execute(PreProcess should complain about using initialization_options and initia
   AssertThrows call ale#linter#PreProcess('testft', g:linter)
   AssertEqual 'Only one of `initialization_options` or `initialization_options_callback` should be set', g:vader_exception
 
-Execute (PreProcess should throw when initialization_options_callback is not a callback):
+Execute(PreProcess should throw when initialization_options_callback is not a callback):
   AssertThrows call ale#linter#PreProcess('testft', {
   \ 'name': 'foo',
   \ 'lsp': 'socket',
@@ -500,3 +500,32 @@ Execute (PreProcess should throw when initialization_options_callback is not a c
   \ 'initialization_options_callback': {},
   \})
   AssertEqual '`initialization_options_callback` must be a callback if defined', g:vader_exception
+
+Execute(PreProcess should accept LSP configuration options via lsp_config):
+  let g:ale_lsp_configuration = {
+  \ 'foo': 'bar'
+  \}
+
+  let g:linter = {
+  \ 'name': 'x',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language_callback': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'lsp_config': g:ale_lsp_configuration,
+  \}
+
+  AssertEqual {'foo': 'bar'}, ale#linter#PreProcess('testft', g:linter).lsp_config
+
+
+Execute(PreProcess should throw when lsp_config is not a Dictionary):
+  AssertThrows call ale#linter#PreProcess('testft', {
+  \ 'name': 'foo',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'lsp_config': 'x',
+  \})
+  AssertEqual '`lsp_config` must be a Dictionary', g:vader_exception
+