python-semver · jimmy-lt · Oct 7, 2018
diff --git a/semver.py b/semver.py
@@ -31,6 +31,18 @@
         $
         """, re.VERBOSE)
 
+_REGEX_PARTIAL = re.compile(
+    r"""
+    ^
+    (?P<major>(?:0|[1-9][0-9]*))
+    (?:
+        \.(?P<minor>(?:0|[1-9][0-9]*))
+    )?
+    $
+    """,
+    re.VERBOSE
+)
+
 _LAST_NUMBER = re.compile(r'(?:[^\d]*(\d+)[^\d]*)+')
 
 if not hasattr(__builtins__, 'cmp'):
@@ -73,6 +85,57 @@ def parse(version):
     return version_parts
 
 
+def try_parse(version):
+    """Try parsing a version string to major, minor, patch, pre-release and
+    build parts. The version string may be incomplete in which case missing
+    parts are set to ``0`` or ``None``.
+
+    :param version: Version string.
+    :type version: str
+
+    :return: Dictionary with the keys 'build', 'major', 'minor', 'patch',
+             and 'prerelease'. The prerelease or build keys can be ``None``
+             if not provided.
+    :rtype: dict
+
+    >>> import semver
+    >>> ver = semver.try_parse('3')
+    >>> ver['major']
+    3
+    >>> ver['minor']
+    0
+    >>> ver['patch']
+    0
+    >>> ver['prerelease'] # None
+    >>> ver['build'] # None
+    >>> ver = semver.try_parse('3.1')
+    >>> ver['major']
+    3
+    >>> ver['minor']
+    1
+    >>> ver['patch']
+    0
+    >>> ver['prerelease'] # None
+    >>> ver['build'] # None
+    """
+    try:
+        return parse(version)
+    except ValueError:
+        match = _REGEX_PARTIAL.match(version)
+        if match is None:
+            raise ValueError('could not parse version string %s' % version)
+
+        version_parts = match.groupdict()
+
+        version_parts['major'] = int(version_parts['major'])
+        version_parts['minor'] = int(version_parts['minor'] or 0)
+        version_parts['patch'] = 0
+        version_parts['prerelease'] = None
+        version_parts['build'] = None
+
+        return version_parts
+
+
 class VersionInfo(object):
     """
     :param int major: version when you make incompatible API changes.

diff --git a/test_semver.py b/test_semver.py
@@ -3,6 +3,7 @@
 from semver import compare
 from semver import match
 from semver import parse
+from semver import try_parse
 from semver import format_version
 from semver import bump_major
 from semver import bump_minor
@@ -79,6 +80,56 @@ def test_should_parse_zero_prerelease(version, expected):
     assert result == expected
 
 
+@pytest.mark.parametrize("version, expected", [
+    # no. 1
+    (
+        "1",
+        {
+            'major': 1,
+            'minor': 0,
+            'patch': 0,
+            'prerelease': None,
+            'build': None,
+        }
+    ),
+    # no. 2
+    (
+        "1.2",
+        {
+            'major': 1,
+            'minor': 2,
+            'patch': 0,
+            'prerelease': None,
+            'build': None,
+        }
+    ),
+    # no. 3
+    (
+        "1.2.3",
+        {
+            'major': 1,
+            'minor': 2,
+            'patch': 3,
+            'prerelease': None,
+            'build': None,
+        }
+    ),
+])
+def test_try_parse_should_allow_partial_version(version, expected):
+    result = try_parse(version)
+    assert result == expected
+
+
+@pytest.mark.parametrize("version", [
+    'foo',
+    '1.x',
+    '1.0.x',
+])
+def test_try_parse_should_raise_value_error_for_invalid_value(version):
+    with pytest.raises(ValueError):
+        try_parse(version)
+
+
 @pytest.mark.parametrize("left,right", [
     ("1.0.0", "2.0.0"),
     ('1.0.0-alpha', '1.0.0-alpha.1'),