convert f-string with nothing to interpolate to regular string

Is your feature request related to a problem? Please describe.

f-strings are great. sometimes they are so great we might use them even when we don’t need to, such as in files where an f-string is used but nothing to interpolate was included in the string body.

Describe the solution you’d like

say you had a python script with a line like this:

hello = f"hello"

black should see that f-string, recognize that it could just be a regular string and drop the f-prefix.

output:

hello = "hello"

Describe alternatives you’ve considered

Could return an error message, but I want black to format for me. Could also not do this, but I think changing to a regular string is a better option.

[dougthor42]

Half the time I forget to add the f prefix. The other half the time I forget to add the curly brackets around my var. I think automatically dropping a “looks useless to me” f prefix is a bad idea. How can black know what the user intended?

print(f"myvar=")
print("{myvar=}")

The same argument applies to the "automatically add f prefix.

Sorry, but 👎 for me.

[vemel]

This can potentially be dangerous for f-strings with brackets.

s = f"this can be safely transformed to a regular string"
s2 = f"Here we have {{double_brackets}}, should they be replaced with single? Who knows..."