get version comparison from semver

since Python is removing version string parsing from the standard library

moves Julia-specific semver utilities to top-level

repo2docker/buildpacks/_r_base.py

@@ -3,7 +3,7 @@ Base information for using R in BuildPacks.
 
 Keeping this in r.py would lead to cyclic imports.
 """
-from distutils.version import LooseVersion as V
+from ..semver import parse_version as V
 
 
 def rstudio_base_scripts(r_version):

repo2docker/buildpacks/julia/julia_project.py

@@ -1,10 +1,13 @@
 """Generates a Dockerfile based on an input matrix for Julia"""
 import functools
 import os
+
 import requests
+import semver
 import toml
+
 from ..python import PythonBuildPack
-from .semver import find_semver_match, semver
+from ...semver import find_semver_match
 
 
 class JuliaProjectTomlBuildPack(PythonBuildPack):

repo2docker/buildpacks/julia/julia_require.py

@@ -1,9 +1,9 @@
 """Generates a Dockerfile based on an input matrix with REQUIRE for legacy Julia"""
 
-from distutils.version import LooseVersion as V
 import os
 
 from ..python import PythonBuildPack
+from ...semver import parse_version as V
 
 
 class JuliaRequireBuildPack(PythonBuildPack):

repo2docker/buildpacks/r.py

@@ -3,8 +3,8 @@ import os
 import datetime
 import requests
 
-from distutils.version import LooseVersion as V
 
+from ..semver import parse_version as V
 from .python import PythonBuildPack
 from ._r_base import rstudio_base_scripts
 

repo2docker/semver.py

@@ -12,11 +12,13 @@ constraints.
 
 
 import re
+from functools import lru_cache
 
 import semver
 
 
 def find_semver_match(constraint, versions_list):
+    """Find first version in a list of versions that matches a constraint"""
     matcher = create_semver_matcher(constraint)
     for vstr in reversed(versions_list):
         if matcher.match(str_to_version(vstr)):
@@ -25,9 +27,29 @@ def find_semver_match(constraint, versions_list):
 
 
 def str_to_version(vstr):
+    """Convert a simple x[.y[.z]] version string to a tuple of ints"""
     return tuple([int(n) for n in vstr.split(".")])
 
 
+@lru_cache()
+def parse_version(vstr):
+    """Convert a simple 'x[.y[.z]]' version string to a comparable VersionInfo
+
+    Wraps semver.VersionInfo.parse with zero-padding,
+    so it can accept '1.0', where upstream only accepts exactly 3 version fields.
+    """
+    try:
+        return semver.VersionInfo.parse(vstr)
+    except ValueError:
+        # may fail for e.g. short 1.0 versions
+        n_fields = vstr.count(".")
+        if n_fields < 2:
+            vstr = vstr + (".0" * (2 - n_fields))
+            return semver.VersionInfo.parse(vstr)
+        else:
+            raise
+
+
 # Helpers
 def major(v):
     return v[0]
@@ -41,6 +63,7 @@ def patch(v):
     return v[2] if len(v) >= 3 else 0
 
 
+@lru_cache()
 def create_semver_matcher(constraint_str):
     """Create a matcher that can be used to match version tuples
 

tests/unit/test_semver.py

@@ -1,5 +1,6 @@
 import pytest
-from repo2docker.buildpacks.julia import semver
+from semver import VersionInfo
+from repo2docker import semver
 
 
 @pytest.mark.parametrize("test_input, expected", [("1.5.2", (1, 5, 2)), ("1", (1,))])
@@ -145,3 +146,20 @@ def test_largerthan_equal():
         semver.create_semver_matcher(">=1.2.3").match(semver.str_to_version("1.2.2"))
         == False
     )
+
+
+@pytest.mark.parametrize(
+    "vstr, expected",
+    [
+        ("1.2.3", "1.2.3"),
+        ("1.2", "1.2.0"),
+        ("1", "1.0.0"),
+    ],
+)
+def test_parse_version(vstr, expected):
+    version_info = semver.parse_version(vstr)
+    assert isinstance(version_info, semver.semver.VersionInfo)
+    assert str(version_info) == expected
+    # satisfies itself, since this is how we use it
+    assert semver.parse_version(expected) <= version_info
+    assert semver.parse_version(expected) >= version_info