remove defaults from optional fields

[dimbleby]

pygls is serializing too many fields

pygls 0.11.0 serializes certain optional fields, regardless of whether the server has explicitly set them - or whether the client has declared support for them.

Updating jedi-language-server to take pygls 0.11.0 I see that we are now returning various fields that we previously didn't eg on CompletionItem we always set deprecated and preselect. I'm pretty sure that this is wrong: not least, there are deprecatedSupport and preselectSupport on CompletionClientCapabilities: if the client has not declared support for these things then presumably we're not supposed to return them.

The approach I have taken is to remove all defaults for Optional fields:

• when the default was not None, this had the effect of making the field not optional after all, as above
• when the default was None it was redundant to declare it as such, so it's just more compact not to bother

This pull request partially undoes f248002. I'm not sure what the motivation for that was, but flagging it in case I've broken something.

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• Tests have been included and/or updated, as appropriate
• Docstrings have been included and/or updated, as appropriate
• Standalone docs have been updated accordingly
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[dimbleby]

I found a handful more places where pygls inserts defaults that are not given by the LSP specification, and removed them.

If this second commit is more controversial than the first then happy to separate the two, but hopefully that's not the case.

[danixeee]

Please check inline comments, I am not sure about default values from the specs.

[danixeee]

Works good, thanks!

[perrinjerome]

This pull request partially undoes f248002. I'm not sure what the motivation for that was, but flagging it in case I've broken something.

@dimbleby it seems this broke progress notification #231 . It seems to be that in this pull request all default values were removed, so maybe it would also be OK to "keep" this code in __init__ ?

[dimbleby]

I think it would be preferable to use pydantic features. Currently we explicitly exclude defaults from serialization -

pygls/pygls/protocol.py

Line 382 in 720da69

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

.

I expect that not doing that should address this?

Then I think we will need to suppress None defaults, but that can be done by exclude_none=True

That is, I think you want this:

diff --git a/pygls/protocol.py b/pygls/protocol.py
index 38d49b0..fa03031 100644
--- a/pygls/protocol.py
+++ b/pygls/protocol.py
@@ -379,7 +379,7 @@ class JsonRPCProtocol(asyncio.Protocol):
             return

         try:
-            body = data.json(by_alias=True, exclude_unset=True, encoder=default_serializer)
+            body = data.json(by_alias=True, exclude_none=True, encoder=default_serializer)
             logger.info('Sending data: %s', body)

             body = body.encode(self.CHARSET)