Function whitespace

src/black/nodes.py:180–428

Return whitespace prefix if needed for the given `leaf`. `complex_subscript` signals whether the given leaf is part of a subscription which has non-trivial arguments, like arithmetic expressions or function calls.

(leaf: Leaf, *, complex_subscript: bool, mode: Mode)

def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:
    class="st">"""Return whitespace prefix if needed for the given `leaf`.

    `complex_subscript` signals whether the given leaf is part of a subscription
    which has non-trivial arguments, like arithmetic expressions or function calls.
    class="st">"""
    NO: Final[str] = class="st">""
    SPACE: Final[str] = class="st">" "
    DOUBLESPACE: Final[str] = class="st">"  "
    t = leaf.type
    p = leaf.parent
    v = leaf.value
    if t in ALWAYS_NO_SPACE:
        return NO

    if t == token.COMMENT:
        return DOUBLESPACE

    assert p is not None, fclass="st">"INTERNAL ERROR: hand-made leaf without parent: {leaf!r}"
    if t == token.COLON and p.type not in {
        syms.subscript,
        syms.subscriptlist,
        syms.sliceop,
    }:
        return NO

    if t == token.LBRACE and p.type in (
        syms.fstring_replacement_field,
        syms.tstring_replacement_field,
    ):
        return NO

    prev = leaf.prev_sibling
    if not prev:
        prevp = preceding_leaf(p)
        if not prevp or prevp.type in OPENING_BRACKETS:
            return NO

        if t == token.COLON:
            if prevp.type == token.COLON:
                return NO

            elif prevp.type != token.COMMA and not complex_subscript:
                return NO

            return SPACE

        if prevp.type == token.EQUAL:
            if prevp.parent:
                if prevp.parent.type in {
                    syms.arglist,
                    syms.argument,
                    syms.parameters,
                    syms.varargslist,
                }:
                    return NO

                elif prevp.parent.type == syms.typedargslist: