Two blank lines after an import should be reduced to one

[kastkeepitjumpinlikekangaroos]

Description

Hey! Trying to contribute for the first time to the project so let me know if I'm missing anything :)

I've implemented changes to address this issue #2020 where there's some inconsistency around how many lines are added after an import. I've added 2 test cases showing that if there is more than 1 blank line between the import and the next line that it is now being reduced to one. One test case was failing because it had in its expected outout 2 lines between the import and following statement, so I think modifying the test case now that it should always be one makes sense.

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[kastkeepitjumpinlikekangaroos]

I got an email about this job failure but looks like all the checks are passing on the PR https://github.com/psf/black/actions/runs/11377698063/job/31652281800 is this something that needs to be addressed?

[JelleZijlstra]

Interesting, I suspect some change to how GitHub handles artifacts. Not sure why it doesn't show up here.

[kastkeepitjumpinlikekangaroos]

I got an email about this job failure but looks like all the checks are passing on the PR https://github.com/psf/black/actions/runs/11377698063/job/31652281800 is this something that needs to be addressed?

I got this same error again on the rerun of the workflows https://github.com/psf/black/actions/runs/11483099904/job/31957735676 and seems to be because there's no artifact in this workflow https://github.com/psf/black/actions/runs/11412528080 with the file name .pr-comment.json. If I'm understanding correctly it looks like this is because these tasks which call comment-body (which produces .pr-comment.json https://github.com/psf/black/blob/main/scripts/diff_shades_gha_helper.py#L167) only executes when the matrix mode is preview-changes and the above diff-shades workflow has a matrix mode of analysis

https://github.com/psf/black/blob/main/.github/workflows/diff_shades.yml#L130:

      - name: Generate summary file (PR only)
        if: github.event_name == 'pull_request' && matrix.mode == 'preview-changes'
        run: >
          python helper.py comment-body
          ${{ matrix.baseline-analysis }} ${{ matrix.target-analysis }}
          ${{ matrix.baseline-sha }} ${{ matrix.target-sha }}
          ${{ github.event.pull_request.number }}

      - name: Upload summary file (PR only)
        if: github.event_name == 'pull_request' && matrix.mode == 'preview-changes'
        uses: actions/upload-artifact@v3
        with:
          name: .pr-comment.json
          path: .pr-comment.json

[kastkeepitjumpinlikekangaroos]

hey @JelleZijlstra ! :) just bumping this PR - do the changes look good or are there other modifications you'd like to see?

[hauntsaninja]

Thanks, this looks reasonable

One nit: could you move the logic down next to

black/src/black/lines.py

Lines 674 to 680 in c98fc0c

	if (
	self.previous_line.is_import
	and not current_line.is_import
	and not current_line.is_fmt_pass_converted(first_leaf_matches=is_import)
	and depth == self.previous_line.depth
	):
	return (before or 1), 0

and also add a test case for when imports are within a function?

[kastkeepitjumpinlikekangaroos]

Thanks, this looks reasonable

One nit: could you move the logic down next to

black/src/black/lines.py

Lines 674 to 680 in c98fc0c

	if (
	self.previous_line.is_import
	and not current_line.is_import
	and not current_line.is_fmt_pass_converted(first_leaf_matches=is_import)
	and depth == self.previous_line.depth
	):
	return (before or 1), 0

and also add a test case for when imports are within a function?

@hauntsaninja for sure, let me know if where I moved the logic is what you were thinking!

also moved all the case cases to a single file, added a test case for imports inside a function, and expanded some existing test cases