Method do_splitter_match

src/black/trans.py:1446–1512

(self, line: Line)

    MIN_SUBSTR_SIZE: Final = 6

    def do_splitter_match(self, line: Line) -> TMatchResult:
        LL = line.leaves

        if self._prefer_paren_wrap_match(LL) is not None:
            return TErr("Line needs to be wrapped in parens first.")

        # If the line is just STRING + COMMA (a one-item tuple) and not inside
        # brackets, we need to defer to StringParenWrapper to wrap it first.
        # Otherwise, splitting the string would create multiple expressions where
        # only the last has the comma, breaking AST equivalence. See issue #4912.
        if (
            not line.inside_brackets
            and len(LL) == 2
            and LL[0].type == token.STRING
            and LL[1].type == token.COMMA
        ):
            return TErr(
                "Line with trailing comma tuple needs to be wrapped in parens first."
            )

        is_valid_index = is_valid_index_factory(LL)

        idx = 0

        # The first two leaves MAY be the 'not in' keywords...
        if (
            is_valid_index(idx)
            and is_valid_index(idx + 1)
            and [LL[idx].type, LL[idx + 1].type] == [token.NAME, token.NAME]
            and str(LL[idx]) + str(LL[idx + 1]) == "not in"
        ):
            idx += 2
        # Else the first leaf MAY be a string operator symbol or the 'in' keyword...
        elif is_valid_index(idx) and (
            LL[idx].type in self.STRING_OPERATORS
            or LL[idx].type == token.NAME
            and str(LL[idx]) == "in"
        ):
            idx += 1

        # The next/first leaf MAY be an empty LPAR...
        if is_valid_index(idx) and is_empty_lpar(LL[idx]):
            idx += 1

        # The next/first leaf MUST be a string...
        if not is_valid_index(idx) or LL[idx].type != token.STRING:
            return TErr("Line does not start with a string.")

        string_idx = idx

        # Skip the string trailer, if one exists.
        string_parser = StringParser()
        idx = string_parser.parse(LL, string_idx)

        # That string MAY be followed by an empty RPAR...
        if is_valid_index(idx) and is_empty_rpar(LL[idx]):
            idx += 1