def _find_name_version_sep(fragment, canonical_name):
    # type: (str, str) -> int
    """Find the separator's index based on the package's canonical name.

    :param fragment: A <package>+<version> filename "fragment" (stem) or
        egg fragment.
    :param canonical_name: The package's canonical name.

    This function is needed since the canonicalized name does not necessarily
    have the same length as the egg info's name part. An example::

    >>> fragment = 'foo__bar-1.0'
    >>> canonical_name = 'foo-bar'
    >>> _find_name_version_sep(fragment, canonical_name)
    8
    """
    # Project name and version must be separated by one single dash. Find all
    # occurrences of dashes; if the string in front of it matches the canonical
    # name, this is the one separating the name and version parts.
    for i, c in enumerate(fragment):
        if c != "-":
            continue
        if canonicalize_name(fragment[:i]) == canonical_name:
            return i
    raise ValueError("{} does not match {}".format(fragment, canonical_name))
Find the separator's index based on the package's canonical name.

    :param fragment: A <package>+<version> filename "fragment" (stem) or
        egg fragment.
    :param canonical_name: The package's canonical name.

    This function is needed since the canonicalized name does not necessarily
    have the same length as the egg info's name part. An example::

    >>> fragment = 'foo__bar-1.0'
    >>> canonical_name = 'foo-bar'
    >>> _find_name_version_sep(fragment, canonical_name)
    8
    
product/gradle-plugin/src/main/python/pip/_internal/index/package_finder.py