fix: resolve several empty line regressions

[finswimmer]

This PR fixes a couple of regressions regarding handling line breaks and empty line.

• If the docstring e.g. for a class is the last thing in the file, don't add any empty lines after it
• If a class or method only contains a docstring, correctly insert empty lines after it
• Treat ... as code lines, so that empty line handling works correct
• Introduce a workaround to detect f-strings in Python < 3.12
• Fixed an issue that arises when line-endings with \r\n are used

Closes: #328

[adamtheturtle]

Thank you @finswimmer , with --black this removes most inconsistencies with black formatting in my project.

One issue remains in my project - when a class is preceded by a comment, black (and docformatter 1.7.7) thinks that there should be two newlines before that comment, but with this PR, docformatter places only one newline before that comment.

Demonstration script:

#!/usr/bin/env bash
set -euo pipefail

DOCFORMATTER_STABLE="docformatter==1.7.7"
DOCFORMATTER_FINSWIMMER_REF="git+https://github.com/finswimmer/docformatter@fea4116e01435bfcce31de936f8549b1b64ca025"

ORIGINAL_CONTENT=$'class A:\n    """Hello."""\n\n\n# Some comment\nclass B:\n    """Hello."""\n'

echo "Initial content:"
printf '%s' "$ORIGINAL_CONTENT"
echo "------"

echo
echo "docformatter stable (${DOCFORMATTER_STABLE}):"
printf '%s' "$ORIGINAL_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_STABLE}" docformatter --black -
echo "------"

echo
echo "docformatter finswimmer (${DOCFORMATTER_FINSWIMMER_REF}):"
printf '%s' "$ORIGINAL_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_FINSWIMMER_REF}" docformatter --black -
echo "------"

Output:

Initial content:
class A:
    """Hello."""


# Some comment
class B:
    """Hello."""
------

docformatter stable (docformatter==1.7.7):
class A:
    """Hello."""


# Some comment
class B:
    """Hello."""
------

docformatter finswimmer (git+https://github.com/finswimmer/docformatter@fea4116e01435bfcce31de936f8549b1b64ca025):
class A:
    """Hello."""

# Some comment
class B:
    """Hello."""
------

[finswimmer]

Thanks a lot for the feedback @adamtheturtle Can you try again please?

[adamtheturtle]

Thank you @finswimmer . The next issues I've hit are demonstrated here.

Failure with CRLF

This errors on this branch.

#!/usr/bin/env bash
set -euo pipefail

DOCFORMATTER_STABLE="docformatter==1.7.7"
DOCFORMATTER_FINSWIMMER_REF="git+https://github.com/finswimmer/docformatter@948c28a5d43106bad3ec796fdf26f87cbdaee085"

ORIGINAL_CONTENT=$'"""\nA\n"""\n\npass\n\npass\n'
CRLF_CONTENT=$(printf '%s' "$ORIGINAL_CONTENT" | sed 's/$/\r/')

echo "Initial content (with CRLF):"
printf '%s' "$CRLF_CONTENT"
echo "------"

echo
echo "docformatter stable (${DOCFORMATTER_STABLE}):"
printf '%s' "$CRLF_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_STABLE}" docformatter --black -
echo "------"

echo
echo "docformatter finswimmer (${DOCFORMATTER_FINSWIMMER_REF}):"
printf '%s' "$CRLF_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_FINSWIMMER_REF}" docformatter --black -
echo "------"

Incompatibility with black

#!/usr/bin/env bash
set -euo pipefail

DOCFORMATTER_STABLE="docformatter==1.7.7"
DOCFORMATTER_FINSWIMMER_REF="git+https://github.com/finswimmer/docformatter@948c28a5d43106bad3ec796fdf26f87cbdaee085"

ORIGINAL_CONTENT=$'"""\nA\n"""\n\npass\n'


echo "Initial content:"
printf '%s' "$ORIGINAL_CONTENT"
echo "------"

echo
echo "docformatter stable (${DOCFORMATTER_STABLE}):"
printf '%s' "$ORIGINAL_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_STABLE}" docformatter --black -
echo "------"

echo
echo "docformatter finswimmer (${DOCFORMATTER_FINSWIMMER_REF}):"
printf '%s' "$ORIGINAL_CONTENT" | uvx --python=3.13 --from "${DOCFORMATTER_FINSWIMMER_REF}" docformatter --black -
echo "------"

Output:

Initial content:
"""
A
"""

pass
------

docformatter stable (docformatter==1.7.7):
"""
A
"""

pass
------

docformatter finswimmer (git+https://github.com/finswimmer/docformatter@948c28a5d43106bad3ec796fdf26f87cbdaee085):
"""
A
"""


pass

This demonstrates that a newline is added. This newline is something that black gets rid of.

[finswimmer]

The CRLF issue should be fixed.

I'm not sure how to handle the conflict with black. The code clearly says, that it will ensure 2 empty line follow the module docstring. I couldn't find enough information what the current behavior of black should. There are some older issue that state that 2 lines are intended, e.g. psf/black#4027 So can you please open a separate issue for this and hopefully @weibullguy can clarify how they like to proceed with this?

fin swimmer

[adamtheturtle]

Thank you @finswimmer . I have created #331.