Implement preview style assignment breaking

[konstin]

Black (and our) stable style:

def f():
    """Black's `Preview.prefer_splitting_right_hand_side_of_assignments`"""
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[
        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    ] = cccccccc.ccccccccccccc.cccccccc

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[
        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    ] = cccccccc.ccccccccccccc().cccccccc

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[
        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    ] = cccccccc.ccccccccccccc(d).cccccccc

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
            cccccccc.ccccccccccccc(d).cccccccc + e
    )

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
            cccccccc.ccccccccccccc.cccccccc + e
    )
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
            cccccccc.ccccccccccccc.cccccccc
            + eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
    )

    self._cache: dict[
        DependencyCacheKey, list[list[DependencyPackage]]
    ] = collections.defaultdict(list)
    self._cached_dependencies_by_level: dict[
        int, list[DependencyCacheKey]
    ] = collections.defaultdict(list)

Preview style, which consistently breaks the right side first:

def f():
    """Black's `Preview.prefer_splitting_right_hand_side_of_assignments`"""
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc.cccccccc
    )

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc().cccccccc
    )

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc(d).cccccccc
    )

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc(d).cccccccc + e
    )

    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc.cccccccc + e
    )
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa[bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb] = (
        cccccccc.ccccccccccccc.cccccccc
        + eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
    )

    self._cache: dict[DependencyCacheKey, list[list[DependencyPackage]]] = (
        collections.defaultdict(list)
    )
    self._cached_dependencies_by_level: dict[int, list[DependencyCacheKey]] = (
        collections.defaultdict(list)
    )

[MichaReiser]

Is this the same as #8043 or any other issue in #6935? If not, could you add it to the umbrella issue?

[konstin]

Thanks, updated #6975