Issue with Python indented structures in JupyterLab

[divyansshhh]

Description

Consider the following snippet -

def fn():
    print("hi")
    for i in range(10):
        print("hello")

If the cursor is at the end of the last line and enter is pressed twice, the user is sent outside the function definition which is unintuitive. Attaching a gif demonstrating this -

This happens even when defining functions in a class.

Reproduce

Expected behavior

I would expect the behavior to be the same as lab3/vscode.

Context

• JupyterLab version: 4.1.5

[krassowski]

For reproduction upstream: Playground example

and with indentOnInput addon.

[krassowski]

Dedenting is intentional in the lang-python implementation by CodeMirror according to this code comment and the reasoning was given here: codemirror/lang-python#4 (comment)

I think this is the worst example, where the user intends to end the block, leave a blank line and start a new block of code but the indentation is forced into alignment with the body:

However, I think that dedent on enter should only move you one block back, not two blocks back. I can reproduce the suboptimal behaviour in CodeMirror playground:

And because there is no dedent when typing function definition (indent on input is not implemented for Python for this case):

The current implementation is de facto fighting the user who tries to add a method to a class definition (whether they decide to add a new line per convention, or to start writing in the first new line they end up with wrong indentation anyways).

I opened an issue upstream to discuss: codemirror/dev#1370