BUG: Missing return statement renders literal "None" instead of erroring

[audreyfeldroy]

Describe the bug

When an endpoint function forgets to return a value (returns None implicitly), AirResponse renders the literal string "None" as HTML content in the browser instead of raising an error.

In src/air/responses.py line 28:

def render(self, tag: BaseTag | str) -> bytes | memoryview:
    return super().render(str(tag))

str(None) produces the string "None", which gets rendered as a 200 OK HTML page.

Steps to reproduce

import air

app = air.Air()

@app.page
def index():
    air.H1("Hello, world!")
    # forgot to return

Visit http://127.0.0.1:8000/ and see the literal text "None" in the browser.

Expected behavior

A missing return should produce a clear error (e.g., TypeError with "endpoint returned None, did you forget a return statement?") rather than silently rendering "None" as page content.

The previous implementation would raise AttributeError on None (because None.render() fails), which was at least a visible error.

Origin

Introduced by PR #377 which changed AirResponse.render to call str(tag) on any input. Found during #1067 investigation.

Affected versions

0.30.0 to present (0.45.0)

[audreyfeldroy]

Resolved by #1106, merged into main as db80a69. Missing returns from both sync and async Air endpoints now raise a clear TypeError, while intentional empty AirResponse() instances remain valid. Closing as completed.