Function return type is missing in the live doc panel

[dimk90]

Describe the bug

The function return type is missing in the live doc panel:

Will you submit a PR?

• Yes

Environment

Details

{
  "marimo": "0.19.9",
  "editable": false,
  "OS": "Linux",
  "OS Version": "6.6.87.2-microsoft-standard-WSL2",
  "Processor": "",
  "Python Version": "3.12.12",
  "Locale": "--",
  "Binaries": {
    "Browser": "--",
    "Node": "v25.2.1"
  },
  "Dependencies": {
    "click": "8.3.1",
    "docutils": "0.22.4",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.10.1",
    "narwhals": "2.16.0",
    "packaging": "26.0",
    "psutil": "7.2.2",
    "pygments": "2.19.2",
    "pymdown-extensions": "10.20.1",
    "pyyaml": "6.0.3",
    "starlette": "0.52.1",
    "tomlkit": "0.14.0",
    "typing-extensions": "4.15.0",
    "uvicorn": "0.40.0",
    "websockets": "16.0"
  },
  "Optional Dependencies": {
    "loro": "1.10.3",
    "openai": "2.17.0",
    "python-lsp-server": "1.14.0"
  },
  "Experimental Flags": {}
}

Code to reproduce

1. Run a simple notebook with 2 cells:

    import marimo
    
    __generated_with = "0.19.9"
    app = marimo.App(width="medium")
    
    @app.cell
    def _():
        import marimo as mo
        return (mo,)
    
    @app.cell
    def _(mo):
        mo.hstack()
        return
    
    if __name__ == "__main__":
        app.run()

2. Open the live doc panel and move the cursor to the hstack function in the second cell.

[mscolnick]

I am unable to reproduce this. @dimk90 can you help us debug a bit more? does it look like the live docs are being cut off? if you inspect the DOM element, is the doc loaded but css off? do you have any LSPs enabled in the configuration settings?

[dimk90]

I've done some additional debugging. The issue persists on my home PC as well, so it's consistent across both machines.

• LSP configuration: I have python-lsp-server enabled on both machines. I disabled it, but the problem remains.
• Custom CSS: I removed my custom.css from the settings (which I use for font customization). The problem still occurs.
• DOM inspection: It seems that part of the documentation is actually missing from the DOM, rather than being a CSS styling issue:

[mscolnick]

i figured out the issue was related to using a newer version of black. i have a fix up now

[mscolnick]

thank you for all the help debugging

[dimk90]

fixed in #8263 (marimo v0.19.10)