Black hangs when using fmt:on/off improperly

[vhoulbreque]

Description

The following code fails:

# -*- coding: utf-8 -*-

setup(
    entry_points={
        # fmt: off
        "console_scripts": [
            "foo-bar"
            "=foo.bar.:main",
        # fmt: on
        ]
    },
)

The following code works:

# -*- coding: utf-8 -*-

setup(
    entry_points={
        # fmt: off
        "console_scripts": [
            "foo-bar"
            "=foo.bar.:main",
        ]
    # fmt: on
    },
)

While running it with these arguments:

$ black file.py

For the first code, there is no error: it just hangs indefinitely. It is also impossible to "CTRL + C" the command.

Expected behavior

Either:

• a fail ("You are using fmt wrong")
• or change the "fmt" functionality to make the first snippet above work.

Environment

• Black's version: 22.3.0
• OS and Python version: Ubuntu 20.04 / 21.04