Parent document completions are showing up in nested documents

[krassowski]

Description

With the completion providers API we cannot suppress the completions from other kernel in transclusions, e.g. in magics like %%sql or %%R.

Reproduce

See that both r2table from R via LSP and range/repr/reversed from Python kernel are showing up.

Expected behavior

Only relevant completions are shown

Context

• JupyterLab version: 4.0.5
• 5.0.0-a1

[krassowski]

We can solve this by overriding isApplicable() in kernel/context provider (because we are overriding them anyways).

[krassowski]

This is not pretty because isApplicable only gets context and not the request position. We can still get the editor position from editor.