String literals concatenated with space between and exceed line length

[dargueta]

The latest versions of black change long string literals with implicit concatenation onto one line, violating line length limits, and leave a space between the string literals. The code was previously formatted by black 19.10b0.

To Reproduce

Given the following code, produced by 19.10b0 ...

assert not extra_files, (
    "Found extra SQL file(s) not in execution manifest for %s: %s. Did you add a"
    " file but forget to put it in the manifest?"
    % (
        os.path.relpath(transform_directory, PROJECT_ROOT),
        ", ".join(repr(f) for f in extra_files),
    )
)

...run a later version on the above code with no arguments and you'll get this:

assert (
    not extra_files
), "Found extra SQL file(s) not in execution manifest for %s: %s. Did you add a" " file but forget to put it in the manifest?" % (
    os.path.relpath(transform_directory, PROJECT_ROOT),
    ", ".join(repr(f) for f in extra_files),
)

For this ticket I'm going to ignore the confusing assertion formatting; see #1483 for that.

There are two things wrong here that I'll concern myself with:

• The new versions appear to have resurrected issue Merge implicitly concatenated string literals that fit on one line #26 by including a space between the string literals that it tried to merge.
• The string literals are forced onto one line, far exceeding the line length limit.

Expected behavior

I would expect the original code to be unmodified, or at the very least be reformatted in a way that 1) doesn't exceed the line length limit and 2) doesn't add a space between two string literals.

Environment (please complete the following information):

• Version: 20.8b0, 20.8b1, 21.5b0, master
• OS: Mac OS 11.2.3
• Python 3.7.6 and 3.8.6

Does this bug also happen on master? Yes

[Jackenmen]

It seems that this no longer causes Black to exceed line length though it does still change this code:

assert not extra_files, (
    "Found extra SQL file(s) not in execution manifest for %s: %s. Did you add a"
    " file but forget to put it in the manifest?"
    % (
        os.path.relpath(transform_directory, PROJECT_ROOT),
        ", ".join(repr(f) for f in extra_files),
    )
)

into:

assert (
    not extra_files
), (
    "Found extra SQL file(s) not in execution manifest for %s: %s. Did you add a"
    " file but forget to put it in the manifest?"
    % (
        os.path.relpath(transform_directory, PROJECT_ROOT),
        ", ".join(repr(f) for f in extra_files),
    )
)

[dargueta]

Confirmed, fixed in the latest release.