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From: tliron <git@git.apache.org>
To: dev@ariatosca.incubator.apache.org
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Subject: [GitHub] incubator-ariatosca pull request #100: ARIA-140 Version utils
Content-Type: text/plain
Message-Id: <20170508161308.F0AA7DFB92@git1-us-west.apache.org>
Date: Mon,  8 May 2017 16:13:08 +0000 (UTC)
archived-at: Mon, 08 May 2017 16:13:13 -0000

Github user tliron commented on a diff in the pull request:

    https://github.com/apache/incubator-ariatosca/pull/100#discussion_r115288142
  
    --- Diff: aria/utils/versions.py ---
    @@ -0,0 +1,162 @@
    +# Licensed to the Apache Software Foundation (ASF) under one or more
    +# contributor license agreements.  See the NOTICE file distributed with
    +# this work for additional information regarding copyright ownership.
    +# The ASF licenses this file to You under the Apache License, Version 2.0
    +# (the "License"); you may not use this file except in compliance with
    +# the License.  You may obtain a copy of the License at
    +#
    +#     http://www.apache.org/licenses/LICENSE-2.0
    +#
    +# Unless required by applicable law or agreed to in writing, software
    +# distributed under the License is distributed on an "AS IS" BASIS,
    +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    +# See the License for the specific language governing permissions and
    +# limitations under the License.
    +
    +"""
    +General-purpose version string handling
    +"""
    +
    +import re
    +
    +
    +_INF = float('inf')
    +
    +_NULL = (), _INF
    +
    +_DIGITS_RE = re.compile(r'^\d+$')
    +
    +_PREFIXES = {
    +    'dev':   0.0001,
    +    'alpha': 0.001,
    +    'beta':  0.01,
    +    'rc':    0.1
    +}
    +
    +
    +class VersionString(unicode):
    +    """
    +    Version string that can be compared, sorted, made unique in a set, and used as a unique dict
    +    key.
    +
    +    The primary part of the string is one or more dot-separated natural numbers. Trailing zeroes
    +    are treated as redundant, e.g. "1.0.0" == "1.0" == "1".
    +
    +    An optional qualifier can be added after a "-". The qualifier can be a natural number or a
    +    specially treated prefixed natural number, e.g. "1.1-beta1" > "1.1-alpha2". The case of the
    +    prefix is ignored.
    +
    +    Numeric qualifiers will always be greater than prefixed integer qualifiers, e.g. "1.1-1" >
    +    "1.1-beta1".
    +
    +    Versions without a qualifier will always be greater than their equivalents with a qualifier,
    +    e.g. e.g. "1.1" > "1.1-1".
    +
    +    Any value that does not conform to this format will be treated as a zero version, which would
    +    be lesser than any non-zero version.
    +
    +    For efficient list sorts use the ``key`` property, e.g.:
    +    ``sorted(versions, key=lambda x: x.key)``
    +    """
    +
    +    NULL = None # initialized below
    +
    +    def __init__(self, value=None):
    +        if value is not None:
    +            super(VersionString, self).__init__(value)
    +        self.key = parse_version_string(self)
    +
    +    def __eq__(self, version):
    +        if not isinstance(version, VersionString):
    +            version = VersionString(version)
    +        return self.key == version.key
    +
    +    def __lt__(self, version):
    +        if not isinstance(version, VersionString):
    +            version = VersionString(version)
    +        return self.key < version.key
    +
    +    def __hash__(self):
    +        return self.key.__hash__()
    +
    +
    +def parse_version_string(version): # pylint: disable=too-many-branches
    +    """
    +    Parses a version string.
    +
    +    :param version: The version string
    +    :returns: The primary tuple and qualifier float
    +    :rtype: ((int), float)
    +    """
    +
    +    if version is None:
    +        return _NULL
    +    version = unicode(version)
    +
    +    # Split to primary and qualifier on '-'
    +    split = version.split('-', 2)
    +    if len(split) == 2:
    +        primary, qualifier = split
    +    else:
    +        primary = split[0]
    +        qualifier = None
    +
    +    # Parse primary
    +    split = primary.split('.')
    +    primary = []
    +    for element in split:
    +        if _DIGITS_RE.match(element) is None:
    +            # Invalid version string
    +            return _NULL
    +        try:
    +            element = int(element)
    +        except ValueError:
    +            # Invalid version string
    +            return _NULL
    +        primary.append(element)
    +
    +    # Remove redundant zeros
    +    for element in reversed(primary):
    +        if element == 0:
    +            primary.pop()
    +        else:
    +            break
    +    primary = tuple(primary)
    +
    +    # Parse qualifier
    +    if qualifier is not None:
    +        if _DIGITS_RE.match(qualifier) is not None:
    +            # Integer qualifer
    +            try:
    +                qualifier = float(int(qualifier))
    +            except ValueError:
    +                # Invalid version string
    +                return _NULL
    +        else:
    +            # Prefixed integer qualifier
    +            value = None
    +            qualifier = qualifier.lower()
    +            for prefix, factor in _PREFIXES.iteritems():
    +                if qualifier.startswith(prefix):
    +                    value = qualifier[len(prefix):]
    +                    if _DIGITS_RE.match(value) is None:
    +                        # Invalid version string
    +                        return _NULL
    +                    try:
    +                        value = float(int(value)) * factor
    +                    except ValueError:
    +                        # Invalid version string
    +                        return _NULL
    +                    break
    +            if value is None:
    +                # Invalid version string
    +                return _NULL
    +            qualifier = value
    +    else:
    +        # Version strings with no qualifiers are higher
    +        qualifier = _INF
    +
    +    return primary, qualifier
    +
    +
    +VersionString.NULL = VersionString()
    --- End diff --
    
    It's a constant for the user to use in any situation where they need a `NULL` value. It's customary to provide singletons for efficiency.


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