Progress notifications does not contain the field kind

[MatejKastak]

WorkDoneProgress* fields kind are excluded when sending to client(editor)

• I think this originated from migration to pydantic
• WorkDoneProgressBegin has field kind with default value 'begin' @ code
• this eventually generates notification @ code
• however the problem is here when model is serialized to json

            body = data.json(by_alias=True, exclude_unset=True, encoder=default_serializer)

• exclude_unset causes the object to ignore kind = 'begin' since it was initialized with default value -- docs
• this is better illustrated in the logs section bellow

Logs

Python code here in the example json-server:

    ls.progress.begin(token, WorkDoneProgressBegin(title='Scan', percentage=0))

Generates the following. Notice how WorkDoneProgressBegin contains kind='begin' (line 1), however the data send does not contain this field (params->value->kind?) (line 2).

Sending notification: "$/progress" token='token' value=WorkDoneProgressBegin(kind='begin', title='Scan', cancellable=None, message=None, percentage=0)
Sending data: {"jsonrpc": "2.0", "method": "$/progress", "params": {"token": "token", "value": {"title": "Scan", "percentage": 0}}}

Solution?

• all of the WorkDoneProgress* messages are affected by this issue
• workaround is to pass kind explicitly, like this PR shows
• I am not sure why we are excluding unset fields.. maybe the solution is to remove exclude_unset option, however this might cause more problems (I am sure there was a reason to put this option there in the first place)
• What do you think? (this PR does not have to be merged, it can be viewed as a demonstration of the problem)

Repro

1. Open json example server
2. Start progress command
3. Observe that there is no task running at the bottom of the window (with name "indexing")

After this PR:

1. Open json example server
2. Start progress command
3. Indexing task is shown

Code review checklist (for code reviewer to complete)

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Commit messages are meaningful (see this for details)
• Tests have been included and/or updated, as appropriate
• Docstrings have been included and/or updated, as appropriate
• Standalone docs have been updated accordingly
• CONTRIBUTORS.md was updated, as appropriate
• Changelog has been updated, as needed (see CHANGELOG.md)

[perrinjerome]

Ah this is same as #231