Completion items getters are not expanded in reconciliator

[krassowski]

Description

The code in the reconciliator uses spread syntax to copy completion item so that it can add a fallback resolve method from provider. This destroys getters.

jupyterlab/packages/completer/src/reconciliator.ts

Lines 61 to 64 in 1d989ba

	const items = reply.items.map(el => ({
	...el,
	resolve: this._resolveFactory(provider, el)
	}));

It is possible to workaround downstream by defining getters as enumerable but this is suboptimal as these will be immediately materialized (so potentially missing opportunity to be populated from resolve request).

Reproduce

1. Create a provider which returns a an item with insertText getter
2. Execute completion
3. See that insertText is undefined and de-duplication does not work

Expected behavior

1. Use Object.assign instead of spread syntax
2. We should test that an instance with getter can be used as completion item
3. Maybe we should avoid creating a copy of completion object in reconciliator in the first place, and internally return a new wrapper object like:

   {
      item: el,
      resolveFallback: this._resolveFactory(provider, el)
   } 

This has a benefit that we could later extend it with renderDocumentation: () => Element so that both LSP markdown-based and kernel sphinx-based docs are rendered properly.

Or, really do we need a factory for a resolve method in the first place? Could we just pass the provider around?

I think that the intent was to later delete the resolve method to mark object as resolved. I do not have a full solution yet.

Context

• JupyterLab version: 4.0.6