indented-form-feed (RUF054)

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for form feed characters preceded by either a space or a tab.

Why is this bad?

The language reference states:

A formfeed character may be present at the start of the line; it will be ignored for the indentation calculations above. Formfeed characters occurring elsewhere in the leading whitespace have an undefined effect (for instance, they may reset the space count to zero).

Example

if foo():\n    \fbar()

Use instead:

if foo():\n    bar()