diff env/lib/python3.9/site-packages/distlib/version.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author shellac
date Mon, 22 Mar 2021 18:12:50 +0000
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/distlib/version.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,736 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2012-2017 The Python Software Foundation.
+# See LICENSE.txt and CONTRIBUTORS.txt.
+#
+"""
+Implementation of a flexible versioning scheme providing support for PEP-440,
+setuptools-compatible and semantic versioning.
+"""
+
+import logging
+import re
+
+from .compat import string_types
+from .util import parse_requirement
+
+__all__ = ['NormalizedVersion', 'NormalizedMatcher',
+           'LegacyVersion', 'LegacyMatcher',
+           'SemanticVersion', 'SemanticMatcher',
+           'UnsupportedVersionError', 'get_scheme']
+
+logger = logging.getLogger(__name__)
+
+
+class UnsupportedVersionError(ValueError):
+    """This is an unsupported version."""
+    pass
+
+
+class Version(object):
+    def __init__(self, s):
+        self._string = s = s.strip()
+        self._parts = parts = self.parse(s)
+        assert isinstance(parts, tuple)
+        assert len(parts) > 0
+
+    def parse(self, s):
+        raise NotImplementedError('please implement in a subclass')
+
+    def _check_compatible(self, other):
+        if type(self) != type(other):
+            raise TypeError('cannot compare %r and %r' % (self, other))
+
+    def __eq__(self, other):
+        self._check_compatible(other)
+        return self._parts == other._parts
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __lt__(self, other):
+        self._check_compatible(other)
+        return self._parts < other._parts
+
+    def __gt__(self, other):
+        return not (self.__lt__(other) or self.__eq__(other))
+
+    def __le__(self, other):
+        return self.__lt__(other) or self.__eq__(other)
+
+    def __ge__(self, other):
+        return self.__gt__(other) or self.__eq__(other)
+
+    # See http://docs.python.org/reference/datamodel#object.__hash__
+    def __hash__(self):
+        return hash(self._parts)
+
+    def __repr__(self):
+        return "%s('%s')" % (self.__class__.__name__, self._string)
+
+    def __str__(self):
+        return self._string
+
+    @property
+    def is_prerelease(self):
+        raise NotImplementedError('Please implement in subclasses.')
+
+
+class Matcher(object):
+    version_class = None
+
+    # value is either a callable or the name of a method
+    _operators = {
+        '<': lambda v, c, p: v < c,
+        '>': lambda v, c, p: v > c,
+        '<=': lambda v, c, p: v == c or v < c,
+        '>=': lambda v, c, p: v == c or v > c,
+        '==': lambda v, c, p: v == c,
+        '===': lambda v, c, p: v == c,
+        # by default, compatible => >=.
+        '~=': lambda v, c, p: v == c or v > c,
+        '!=': lambda v, c, p: v != c,
+    }
+
+    # this is a method only to support alternative implementations
+    # via overriding
+    def parse_requirement(self, s):
+        return parse_requirement(s)
+
+    def __init__(self, s):
+        if self.version_class is None:
+            raise ValueError('Please specify a version class')
+        self._string = s = s.strip()
+        r = self.parse_requirement(s)
+        if not r:
+            raise ValueError('Not valid: %r' % s)
+        self.name = r.name
+        self.key = self.name.lower()    # for case-insensitive comparisons
+        clist = []
+        if r.constraints:
+            # import pdb; pdb.set_trace()
+            for op, s in r.constraints:
+                if s.endswith('.*'):
+                    if op not in ('==', '!='):
+                        raise ValueError('\'.*\' not allowed for '
+                                         '%r constraints' % op)
+                    # Could be a partial version (e.g. for '2.*') which
+                    # won't parse as a version, so keep it as a string
+                    vn, prefix = s[:-2], True
+                    # Just to check that vn is a valid version
+                    self.version_class(vn)
+                else:
+                    # Should parse as a version, so we can create an
+                    # instance for the comparison
+                    vn, prefix = self.version_class(s), False
+                clist.append((op, vn, prefix))
+        self._parts = tuple(clist)
+
+    def match(self, version):
+        """
+        Check if the provided version matches the constraints.
+
+        :param version: The version to match against this instance.
+        :type version: String or :class:`Version` instance.
+        """
+        if isinstance(version, string_types):
+            version = self.version_class(version)
+        for operator, constraint, prefix in self._parts:
+            f = self._operators.get(operator)
+            if isinstance(f, string_types):
+                f = getattr(self, f)
+            if not f:
+                msg = ('%r not implemented '
+                       'for %s' % (operator, self.__class__.__name__))
+                raise NotImplementedError(msg)
+            if not f(version, constraint, prefix):
+                return False
+        return True
+
+    @property
+    def exact_version(self):
+        result = None
+        if len(self._parts) == 1 and self._parts[0][0] in ('==', '==='):
+            result = self._parts[0][1]
+        return result
+
+    def _check_compatible(self, other):
+        if type(self) != type(other) or self.name != other.name:
+            raise TypeError('cannot compare %s and %s' % (self, other))
+
+    def __eq__(self, other):
+        self._check_compatible(other)
+        return self.key == other.key and self._parts == other._parts
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    # See http://docs.python.org/reference/datamodel#object.__hash__
+    def __hash__(self):
+        return hash(self.key) + hash(self._parts)
+
+    def __repr__(self):
+        return "%s(%r)" % (self.__class__.__name__, self._string)
+
+    def __str__(self):
+        return self._string
+
+
+PEP440_VERSION_RE = re.compile(r'^v?(\d+!)?(\d+(\.\d+)*)((a|b|c|rc)(\d+))?'
+                               r'(\.(post)(\d+))?(\.(dev)(\d+))?'
+                               r'(\+([a-zA-Z\d]+(\.[a-zA-Z\d]+)?))?$')
+
+
+def _pep_440_key(s):
+    s = s.strip()
+    m = PEP440_VERSION_RE.match(s)
+    if not m:
+        raise UnsupportedVersionError('Not a valid version: %s' % s)
+    groups = m.groups()
+    nums = tuple(int(v) for v in groups[1].split('.'))
+    while len(nums) > 1 and nums[-1] == 0:
+        nums = nums[:-1]
+
+    if not groups[0]:
+        epoch = 0
+    else:
+        epoch = int(groups[0])
+    pre = groups[4:6]
+    post = groups[7:9]
+    dev = groups[10:12]
+    local = groups[13]
+    if pre == (None, None):
+        pre = ()
+    else:
+        pre = pre[0], int(pre[1])
+    if post == (None, None):
+        post = ()
+    else:
+        post = post[0], int(post[1])
+    if dev == (None, None):
+        dev = ()
+    else:
+        dev = dev[0], int(dev[1])
+    if local is None:
+        local = ()
+    else:
+        parts = []
+        for part in local.split('.'):
+            # to ensure that numeric compares as > lexicographic, avoid
+            # comparing them directly, but encode a tuple which ensures
+            # correct sorting
+            if part.isdigit():
+                part = (1, int(part))
+            else:
+                part = (0, part)
+            parts.append(part)
+        local = tuple(parts)
+    if not pre:
+        # either before pre-release, or final release and after
+        if not post and dev:
+            # before pre-release
+            pre = ('a', -1)     # to sort before a0
+        else:
+            pre = ('z',)        # to sort after all pre-releases
+    # now look at the state of post and dev.
+    if not post:
+        post = ('_',)   # sort before 'a'
+    if not dev:
+        dev = ('final',)
+
+    #print('%s -> %s' % (s, m.groups()))
+    return epoch, nums, pre, post, dev, local
+
+
+_normalized_key = _pep_440_key
+
+
+class NormalizedVersion(Version):
+    """A rational version.
+
+    Good:
+        1.2         # equivalent to "1.2.0"
+        1.2.0
+        1.2a1
+        1.2.3a2
+        1.2.3b1
+        1.2.3c1
+        1.2.3.4
+        TODO: fill this out
+
+    Bad:
+        1           # minimum two numbers
+        1.2a        # release level must have a release serial
+        1.2.3b
+    """
+    def parse(self, s):
+        result = _normalized_key(s)
+        # _normalized_key loses trailing zeroes in the release
+        # clause, since that's needed to ensure that X.Y == X.Y.0 == X.Y.0.0
+        # However, PEP 440 prefix matching needs it: for example,
+        # (~= 1.4.5.0) matches differently to (~= 1.4.5.0.0).
+        m = PEP440_VERSION_RE.match(s)      # must succeed
+        groups = m.groups()
+        self._release_clause = tuple(int(v) for v in groups[1].split('.'))
+        return result
+
+    PREREL_TAGS = set(['a', 'b', 'c', 'rc', 'dev'])
+
+    @property
+    def is_prerelease(self):
+        return any(t[0] in self.PREREL_TAGS for t in self._parts if t)
+
+
+def _match_prefix(x, y):
+    x = str(x)
+    y = str(y)
+    if x == y:
+        return True
+    if not x.startswith(y):
+        return False
+    n = len(y)
+    return x[n] == '.'
+
+
+class NormalizedMatcher(Matcher):
+    version_class = NormalizedVersion
+
+    # value is either a callable or the name of a method
+    _operators = {
+        '~=': '_match_compatible',
+        '<': '_match_lt',
+        '>': '_match_gt',
+        '<=': '_match_le',
+        '>=': '_match_ge',
+        '==': '_match_eq',
+        '===': '_match_arbitrary',
+        '!=': '_match_ne',
+    }
+
+    def _adjust_local(self, version, constraint, prefix):
+        if prefix:
+            strip_local = '+' not in constraint and version._parts[-1]
+        else:
+            # both constraint and version are
+            # NormalizedVersion instances.
+            # If constraint does not have a local component,
+            # ensure the version doesn't, either.
+            strip_local = not constraint._parts[-1] and version._parts[-1]
+        if strip_local:
+            s = version._string.split('+', 1)[0]
+            version = self.version_class(s)
+        return version, constraint
+
+    def _match_lt(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        if version >= constraint:
+            return False
+        release_clause = constraint._release_clause
+        pfx = '.'.join([str(i) for i in release_clause])
+        return not _match_prefix(version, pfx)
+
+    def _match_gt(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        if version <= constraint:
+            return False
+        release_clause = constraint._release_clause
+        pfx = '.'.join([str(i) for i in release_clause])
+        return not _match_prefix(version, pfx)
+
+    def _match_le(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        return version <= constraint
+
+    def _match_ge(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        return version >= constraint
+
+    def _match_eq(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        if not prefix:
+            result = (version == constraint)
+        else:
+            result = _match_prefix(version, constraint)
+        return result
+
+    def _match_arbitrary(self, version, constraint, prefix):
+        return str(version) == str(constraint)
+
+    def _match_ne(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        if not prefix:
+            result = (version != constraint)
+        else:
+            result = not _match_prefix(version, constraint)
+        return result
+
+    def _match_compatible(self, version, constraint, prefix):
+        version, constraint = self._adjust_local(version, constraint, prefix)
+        if version == constraint:
+            return True
+        if version < constraint:
+            return False
+#        if not prefix:
+#            return True
+        release_clause = constraint._release_clause
+        if len(release_clause) > 1:
+            release_clause = release_clause[:-1]
+        pfx = '.'.join([str(i) for i in release_clause])
+        return _match_prefix(version, pfx)
+
+_REPLACEMENTS = (
+    (re.compile('[.+-]$'), ''),                     # remove trailing puncts
+    (re.compile(r'^[.](\d)'), r'0.\1'),             # .N -> 0.N at start
+    (re.compile('^[.-]'), ''),                      # remove leading puncts
+    (re.compile(r'^\((.*)\)$'), r'\1'),             # remove parentheses
+    (re.compile(r'^v(ersion)?\s*(\d+)'), r'\2'),    # remove leading v(ersion)
+    (re.compile(r'^r(ev)?\s*(\d+)'), r'\2'),        # remove leading v(ersion)
+    (re.compile('[.]{2,}'), '.'),                   # multiple runs of '.'
+    (re.compile(r'\b(alfa|apha)\b'), 'alpha'),      # misspelt alpha
+    (re.compile(r'\b(pre-alpha|prealpha)\b'),
+                'pre.alpha'),                       # standardise
+    (re.compile(r'\(beta\)$'), 'beta'),             # remove parentheses
+)
+
+_SUFFIX_REPLACEMENTS = (
+    (re.compile('^[:~._+-]+'), ''),                   # remove leading puncts
+    (re.compile('[,*")([\\]]'), ''),                  # remove unwanted chars
+    (re.compile('[~:+_ -]'), '.'),                    # replace illegal chars
+    (re.compile('[.]{2,}'), '.'),                   # multiple runs of '.'
+    (re.compile(r'\.$'), ''),                       # trailing '.'
+)
+
+_NUMERIC_PREFIX = re.compile(r'(\d+(\.\d+)*)')
+
+
+def _suggest_semantic_version(s):
+    """
+    Try to suggest a semantic form for a version for which
+    _suggest_normalized_version couldn't come up with anything.
+    """
+    result = s.strip().lower()
+    for pat, repl in _REPLACEMENTS:
+        result = pat.sub(repl, result)
+    if not result:
+        result = '0.0.0'
+
+    # Now look for numeric prefix, and separate it out from
+    # the rest.
+    #import pdb; pdb.set_trace()
+    m = _NUMERIC_PREFIX.match(result)
+    if not m:
+        prefix = '0.0.0'
+        suffix = result
+    else:
+        prefix = m.groups()[0].split('.')
+        prefix = [int(i) for i in prefix]
+        while len(prefix) < 3:
+            prefix.append(0)
+        if len(prefix) == 3:
+            suffix = result[m.end():]
+        else:
+            suffix = '.'.join([str(i) for i in prefix[3:]]) + result[m.end():]
+            prefix = prefix[:3]
+        prefix = '.'.join([str(i) for i in prefix])
+        suffix = suffix.strip()
+    if suffix:
+        #import pdb; pdb.set_trace()
+        # massage the suffix.
+        for pat, repl in _SUFFIX_REPLACEMENTS:
+            suffix = pat.sub(repl, suffix)
+
+    if not suffix:
+        result = prefix
+    else:
+        sep = '-' if 'dev' in suffix else '+'
+        result = prefix + sep + suffix
+    if not is_semver(result):
+        result = None
+    return result
+
+
+def _suggest_normalized_version(s):
+    """Suggest a normalized version close to the given version string.
+
+    If you have a version string that isn't rational (i.e. NormalizedVersion
+    doesn't like it) then you might be able to get an equivalent (or close)
+    rational version from this function.
+
+    This does a number of simple normalizations to the given string, based
+    on observation of versions currently in use on PyPI. Given a dump of
+    those version during PyCon 2009, 4287 of them:
+    - 2312 (53.93%) match NormalizedVersion without change
+      with the automatic suggestion
+    - 3474 (81.04%) match when using this suggestion method
+
+    @param s {str} An irrational version string.
+    @returns A rational version string, or None, if couldn't determine one.
+    """
+    try:
+        _normalized_key(s)
+        return s   # already rational
+    except UnsupportedVersionError:
+        pass
+
+    rs = s.lower()
+
+    # part of this could use maketrans
+    for orig, repl in (('-alpha', 'a'), ('-beta', 'b'), ('alpha', 'a'),
+                       ('beta', 'b'), ('rc', 'c'), ('-final', ''),
+                       ('-pre', 'c'),
+                       ('-release', ''), ('.release', ''), ('-stable', ''),
+                       ('+', '.'), ('_', '.'), (' ', ''), ('.final', ''),
+                       ('final', '')):
+        rs = rs.replace(orig, repl)
+
+    # if something ends with dev or pre, we add a 0
+    rs = re.sub(r"pre$", r"pre0", rs)
+    rs = re.sub(r"dev$", r"dev0", rs)
+
+    # if we have something like "b-2" or "a.2" at the end of the
+    # version, that is probably beta, alpha, etc
+    # let's remove the dash or dot
+    rs = re.sub(r"([abc]|rc)[\-\.](\d+)$", r"\1\2", rs)
+
+    # 1.0-dev-r371 -> 1.0.dev371
+    # 0.1-dev-r79 -> 0.1.dev79
+    rs = re.sub(r"[\-\.](dev)[\-\.]?r?(\d+)$", r".\1\2", rs)
+
+    # Clean: 2.0.a.3, 2.0.b1, 0.9.0~c1
+    rs = re.sub(r"[.~]?([abc])\.?", r"\1", rs)
+
+    # Clean: v0.3, v1.0
+    if rs.startswith('v'):
+        rs = rs[1:]
+
+    # Clean leading '0's on numbers.
+    #TODO: unintended side-effect on, e.g., "2003.05.09"
+    # PyPI stats: 77 (~2%) better
+    rs = re.sub(r"\b0+(\d+)(?!\d)", r"\1", rs)
+
+    # Clean a/b/c with no version. E.g. "1.0a" -> "1.0a0". Setuptools infers
+    # zero.
+    # PyPI stats: 245 (7.56%) better
+    rs = re.sub(r"(\d+[abc])$", r"\g<1>0", rs)
+
+    # the 'dev-rNNN' tag is a dev tag
+    rs = re.sub(r"\.?(dev-r|dev\.r)\.?(\d+)$", r".dev\2", rs)
+
+    # clean the - when used as a pre delimiter
+    rs = re.sub(r"-(a|b|c)(\d+)$", r"\1\2", rs)
+
+    # a terminal "dev" or "devel" can be changed into ".dev0"
+    rs = re.sub(r"[\.\-](dev|devel)$", r".dev0", rs)
+
+    # a terminal "dev" can be changed into ".dev0"
+    rs = re.sub(r"(?![\.\-])dev$", r".dev0", rs)
+
+    # a terminal "final" or "stable" can be removed
+    rs = re.sub(r"(final|stable)$", "", rs)
+
+    # The 'r' and the '-' tags are post release tags
+    #   0.4a1.r10       ->  0.4a1.post10
+    #   0.9.33-17222    ->  0.9.33.post17222
+    #   0.9.33-r17222   ->  0.9.33.post17222
+    rs = re.sub(r"\.?(r|-|-r)\.?(\d+)$", r".post\2", rs)
+
+    # Clean 'r' instead of 'dev' usage:
+    #   0.9.33+r17222   ->  0.9.33.dev17222
+    #   1.0dev123       ->  1.0.dev123
+    #   1.0.git123      ->  1.0.dev123
+    #   1.0.bzr123      ->  1.0.dev123
+    #   0.1a0dev.123    ->  0.1a0.dev123
+    # PyPI stats:  ~150 (~4%) better
+    rs = re.sub(r"\.?(dev|git|bzr)\.?(\d+)$", r".dev\2", rs)
+
+    # Clean '.pre' (normalized from '-pre' above) instead of 'c' usage:
+    #   0.2.pre1        ->  0.2c1
+    #   0.2-c1         ->  0.2c1
+    #   1.0preview123   ->  1.0c123
+    # PyPI stats: ~21 (0.62%) better
+    rs = re.sub(r"\.?(pre|preview|-c)(\d+)$", r"c\g<2>", rs)
+
+    # Tcl/Tk uses "px" for their post release markers
+    rs = re.sub(r"p(\d+)$", r".post\1", rs)
+
+    try:
+        _normalized_key(rs)
+    except UnsupportedVersionError:
+        rs = None
+    return rs
+
+#
+#   Legacy version processing (distribute-compatible)
+#
+
+_VERSION_PART = re.compile(r'([a-z]+|\d+|[\.-])', re.I)
+_VERSION_REPLACE = {
+    'pre': 'c',
+    'preview': 'c',
+    '-': 'final-',
+    'rc': 'c',
+    'dev': '@',
+    '': None,
+    '.': None,
+}
+
+
+def _legacy_key(s):
+    def get_parts(s):
+        result = []
+        for p in _VERSION_PART.split(s.lower()):
+            p = _VERSION_REPLACE.get(p, p)
+            if p:
+                if '0' <= p[:1] <= '9':
+                    p = p.zfill(8)
+                else:
+                    p = '*' + p
+                result.append(p)
+        result.append('*final')
+        return result
+
+    result = []
+    for p in get_parts(s):
+        if p.startswith('*'):
+            if p < '*final':
+                while result and result[-1] == '*final-':
+                    result.pop()
+            while result and result[-1] == '00000000':
+                result.pop()
+        result.append(p)
+    return tuple(result)
+
+
+class LegacyVersion(Version):
+    def parse(self, s):
+        return _legacy_key(s)
+
+    @property
+    def is_prerelease(self):
+        result = False
+        for x in self._parts:
+            if (isinstance(x, string_types) and x.startswith('*') and
+                x < '*final'):
+                result = True
+                break
+        return result
+
+
+class LegacyMatcher(Matcher):
+    version_class = LegacyVersion
+
+    _operators = dict(Matcher._operators)
+    _operators['~='] = '_match_compatible'
+
+    numeric_re = re.compile(r'^(\d+(\.\d+)*)')
+
+    def _match_compatible(self, version, constraint, prefix):
+        if version < constraint:
+            return False
+        m = self.numeric_re.match(str(constraint))
+        if not m:
+            logger.warning('Cannot compute compatible match for version %s '
+                           ' and constraint %s', version, constraint)
+            return True
+        s = m.groups()[0]
+        if '.' in s:
+            s = s.rsplit('.', 1)[0]
+        return _match_prefix(version, s)
+
+#
+#   Semantic versioning
+#
+
+_SEMVER_RE = re.compile(r'^(\d+)\.(\d+)\.(\d+)'
+                        r'(-[a-z0-9]+(\.[a-z0-9-]+)*)?'
+                        r'(\+[a-z0-9]+(\.[a-z0-9-]+)*)?$', re.I)
+
+
+def is_semver(s):
+    return _SEMVER_RE.match(s)
+
+
+def _semantic_key(s):
+    def make_tuple(s, absent):
+        if s is None:
+            result = (absent,)
+        else:
+            parts = s[1:].split('.')
+            # We can't compare ints and strings on Python 3, so fudge it
+            # by zero-filling numeric values so simulate a numeric comparison
+            result = tuple([p.zfill(8) if p.isdigit() else p for p in parts])
+        return result
+
+    m = is_semver(s)
+    if not m:
+        raise UnsupportedVersionError(s)
+    groups = m.groups()
+    major, minor, patch = [int(i) for i in groups[:3]]
+    # choose the '|' and '*' so that versions sort correctly
+    pre, build = make_tuple(groups[3], '|'), make_tuple(groups[5], '*')
+    return (major, minor, patch), pre, build
+
+
+class SemanticVersion(Version):
+    def parse(self, s):
+        return _semantic_key(s)
+
+    @property
+    def is_prerelease(self):
+        return self._parts[1][0] != '|'
+
+
+class SemanticMatcher(Matcher):
+    version_class = SemanticVersion
+
+
+class VersionScheme(object):
+    def __init__(self, key, matcher, suggester=None):
+        self.key = key
+        self.matcher = matcher
+        self.suggester = suggester
+
+    def is_valid_version(self, s):
+        try:
+            self.matcher.version_class(s)
+            result = True
+        except UnsupportedVersionError:
+            result = False
+        return result
+
+    def is_valid_matcher(self, s):
+        try:
+            self.matcher(s)
+            result = True
+        except UnsupportedVersionError:
+            result = False
+        return result
+
+    def is_valid_constraint_list(self, s):
+        """
+        Used for processing some metadata fields
+        """
+        return self.is_valid_matcher('dummy_name (%s)' % s)
+
+    def suggest(self, s):
+        if self.suggester is None:
+            result = None
+        else:
+            result = self.suggester(s)
+        return result
+
+_SCHEMES = {
+    'normalized': VersionScheme(_normalized_key, NormalizedMatcher,
+                                _suggest_normalized_version),
+    'legacy': VersionScheme(_legacy_key, LegacyMatcher, lambda self, s: s),
+    'semantic': VersionScheme(_semantic_key, SemanticMatcher,
+                              _suggest_semantic_version),
+}
+
+_SCHEMES['default'] = _SCHEMES['normalized']
+
+
+def get_scheme(name):
+    if name not in _SCHEMES:
+        raise ValueError('unknown scheme name: %r' % name)
+    return _SCHEMES[name]