Don't send not specified properties

[muffinmad]

E.g.

types.Completion('defaultdict')

will result in sending all other attributes along with label:

server-reply (id:21) Wed May 13 14:25:56 2020:
(:id 21 :jsonrpc "2.0" :result
     (:isIncomplete :json-false :items
		    [(:label "defaultdict" :kind nil :detail nil :documentation nil :deprecated :json-false :preselect :json-false :sortText nil :filterText nil :insertText nil :insertTextFormat nil :textEdit nil :additionalTextEdits nil :commitCharacters nil :command nil :data nil)]))

[rwols]

Important notions from the LSP spec:

• There can be an optional key with a valid value.
• There can be a mandatory key with an optional value. doesn't seem to be the case

[rwols]

There's also a "range": null in the response to the textDocument/hover request. I'm guessing it's the same underlying issue.

This library needs to distinguish between optional keys with typed values and mandatory keys.

[rwols]

I haven't tested this but this might work as serializer:

def default_serializer(o):
    """JSON serializer for complex objects."""
    if isinstance(o, enum.Enum):
        return o.value
    d = {}
    for k, v in o.__dict__.items():
        if not k.startswith('_') and v is not None:
            d[k] = v
    return d

[rwols]

You should also account for cases where a None response is allowed:

• textDocument/hover is allowed to respond with None if there's no hover.
• textDocument/signatureHelp is allowed to respond with None if there's no sighelp.
• ...

[rwols]

Another example where this breaks an editor is for textDocument/rename. We do a check here to see if we're dealing with new-style documentChanges or old-style changes:

def parse_workspace_edit(workspace_edit: Dict[str, Any]) -> Dict[str, List[TextEdit]]:
    changes = {}  # type: Dict[str, List[TextEdit]]
    if 'changes' in workspace_edit:
        for uri, file_changes in workspace_edit.get('changes', {}).items():
            changes[uri_to_filename(uri)] = list(parse_text_edit(change) for change in file_changes)
    if 'documentChanges' in workspace_edit:
        for document_change in workspace_edit.get('documentChanges', []):
            if 'kind' in document_change:
                debug('Ignoring unsupported "resourceOperations" edit type')
                continue
            uri = document_change.get('textDocument').get('uri')
            version = document_change.get('textDocument').get('version')
            text_edit = list(parse_text_edit(change, version) for change in document_change.get('edits'))
            changes[uri_to_filename(uri)] = text_edit
    return changes

However, the payload from this framework is

{'changes': None, 'documentChanges': [{'edits': [{'newText': "                filename = cls.name()\n                if filename.lower().startswith('lsp-'):\n                    filename = filename[len('lsp-'):]\n                sublime.find_resources('*{}.sublime-settings'.format(filename))\n", 'range': {'end': {'character': 0, 'line': 68}, 'start': {'character': 0, 'line': 64}}}], 'textDocument': {'version': 149, 'uri': 'file:///home/raoul/.config/sublime-text-3/Packages/LSP/plugin/core/main.py'}}]}

changes is in the returned params, so we will break in if 'changes' in workspace_edit. It's not allowed per spec to have None as value.

[muffinmad]

@rwols Because both 'changes' and 'documentChanges' are processed, simple workaround may help, e.g.:

 def parse_workspace_edit(workspace_edit: Dict[str, Any]) -> Dict[str, List[TextEdit]]:
     changes = {}  # type: Dict[str, List[TextEdit]]
-    if 'changes' in workspace_edit:
-        for uri, file_changes in workspace_edit.get('changes', {}).items():
+    _changes = workspace_edit.get('changes')
+    if _changes:
+        for uri, file_changes in _changes.items():
             changes[uri_to_filename(uri)] = list(parse_text_edit(change) for change in file_changes)
-    if 'documentChanges' in workspace_edit:
-        for document_change in workspace_edit.get('documentChanges', []):
+    _changes = workspace_edit.get('documentChanges')
+    if _changes:
+        for document_change in _changes:
             if 'kind' in document_change:
                 debug('Ignoring unsupported "resourceOperations" edit type')
                 continue

[pappasam]

@danixeee Another option is to have a library-specific value for an optionally undefined attribute:

UNDEFINED = object()

In the serializer, you can do an identity is check for UNDEFINED and not return it if the object is undefined:

def default_serializer(o):
    """JSON serializer for complex objects."""
    if isinstance(o, enum.Enum):
        return o.value
    d = {}
    for k, v in o.__dict__.items():
        if v is not UNDEFINED:
            d[k] = v
    return d

The above will still allow None to be placed into the dictionary.

I was drawn to this conversation by the following issue: pappasam/jedi-language-server#38 (comment)

Here's a mypy-friendly way of achieving the above: https://www.python.org/dev/peps/pep-0484/#support-for-singleton-types-in-unions

[danixeee]

Solved with #139.