allow generic LSP config to specify trigger characters to override server

Author: puremourning

README.md

@@ -285,14 +285,18 @@ wouldn't usually know about. The value is a list of dictionaries containing:
 - `capabilities'`: Overrides the default LSP capabilities of ycmd.
   - If you enable `workspace/configuration` support, check the extra conf
     details, relevant to LSP servers.
+- `triggerCharacters`: Override the LSP server's trigger characters for
+  completion. This can be useful when the server obnoxiously requests completion
+  on every character or for example on whitespace characters.
 
 ```json
 {
   "language_server": [ {
     "name": "gopls",
     "cmdline": [ "/path/to/gopls", "-rpc.trace" ],
     "filetypes": [ "go" ],
-    "project_root_files": [ "go.mod" ]
+    "project_root_files": [ "go.mod" ],
+    "tirggerCharacters": [ "." ]
   } ]
 }
 ```

ycmd/completers/language_server/generic_lsp_completer.py

@@ -32,6 +32,8 @@ def __init__( self, user_options, server_settings ):
 
     self._command_line = server_settings.get( 'cmdline' )
 
+    self._server_settings = server_settings
+
     self._port = server_settings.get( 'port' )
     if self._port:
       connection_type = 'tcp'
@@ -121,3 +123,8 @@ def WorkspaceConfigurationResponse( self, request ):
       sections_to_config_map = self._settings.get( 'config_sections', {} )
       return [ sections_to_config_map.get( item.get( 'section', '' ) )
                for item in request[ 'params' ][ 'items' ] ]
+
+
+  def GetTriggerCharacters( self, server_trigger_characters ):
+    return self._server_settings.get( 'triggerCharacters',
+                                      server_trigger_characters )

ycmd/tests/go/diagnostics_test.py

@@ -71,8 +71,10 @@ def test_Diagnostics_DetailedDiags( self, app ):
 
     results = app.post_json( '/detailed_diagnostic', request_data ).json
     assert_that( results,
-                 any_of( has_entry( 'message', 'undeclared name: diagnostics_test' ),
-                         has_entry( 'message', 'undefined: diagnostics_test' ) ) )
+                 any_of( has_entry( 'message',
+                                    'undeclared name: diagnostics_test' ),
+                         has_entry( 'message',
+                                    'undefined: diagnostics_test' ) ) )
 
 
   @WithRetry()