SageMath uses python lsp, and reports a lot of errors

[anstadnik]

Description

Here, it complains about the undefined name "matrix"

Reproduce

1. Install SageMath
2. Install jupyterlab-lsp
3. Write SageMath code
4. Observe the errors

Expected behavior

LSP should be turned off by default.

Context

• Operating System and version: Arch linux
• Browser and version: Chrome
• JupyterLab version: 3.4.3
• Language server and version:

Required: installed server extensions

```
    jupyter_lsp enabled
    - Validating jupyter_lsp...
      jupyter_lsp 1.5.1 OK
    jupyter_server_mathjax enabled
    - Validating jupyter_server_mathjax...
      jupyter_server_mathjax  OK
    jupyterlab enabled
    - Validating jupyterlab...
      jupyterlab 3.4.3 OK
    jupyterlab_code_formatter enabled
    - Validating jupyterlab_code_formatter...
      jupyterlab_code_formatter 1.4.10 OK
    jupytext enabled
    - Validating jupytext...
      jupytext 1.11.5 OK
    nbclassic enabled
    - Validating nbclassic...
      nbclassic  OK
    nbdime enabled
    - Validating nbdime...
      nbdime 3.1.1 OK

Config dir: /usr/local/etc/jupyter
```

Required: installed lab extensions

```
        jupyterlab-plotly v5.5.0 enabled OK
        nbdime-jupyterlab v2.1.1 enabled OK
        jupyterlab-jupytext v1.3.4 enabled OK (python, jupytext)
        @jupyter-widgets/jupyterlab-manager v3.0.1 enabled OK (python, jupyterlab_widgets)
        @ryantam626/jupyterlab_code_formatter v1.4.10 enabled OK (python, jupyterlab-code-formatter)
        @krassowski/jupyterlab-lsp v3.10.1 enabled OK (python, jupyterlab-lsp)
```

Troubleshoot Output

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Command Line Output

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[krassowski]

Is SageMath shipping a custom kernel which defines these variables? If so, it probably should not advertise that it uses Python language as standard Python does not have matrix built-in.

[krassowski]

It looks that SageMath does not populate language_info the way one would expect (it always populates it with Python as name of language). In jupytext, https://github.com/mwouts/jupytext/pull/732 workarounds this by using language from kernel specs instead, which could be used in jupyterlab-lsp too.