Implement pep 503 data-requires-python

pip/index.py

@@ -22,6 +22,7 @@
 )
 from pip.utils.deprecation import RemovedInPip9Warning, RemovedInPip10Warning
 from pip.utils.logging import indent_log
+from pip.utils.packaging import check_requires_python
 from pip.exceptions import (
     DistributionNotFound, BestVersionAlreadyInstalled, InvalidWheelFilename,
     UnsupportedWheel,
@@ -33,6 +34,7 @@
 from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.requests.exceptions import SSLError
+from pip._vendor.distlib.compat import unescape
 
 
 __all__ = ['FormatControl', 'fmt_ctl_handle_mutual_exclude', 'PackageFinder']
@@ -640,6 +642,12 @@ def _link_package_versions(self, link, search):
                 self._log_skipped_link(
                     link, 'Python version is incorrect')
                 return
+
+        if not check_requires_python(link.requires_python):
+            logger.debug("The package %s is incompatible with the python"
+                         "version in use. Acceptable python versions are:%s",
+                         link, link.requires_python)
+            return
         logger.debug('Found link %s, version: %s', link, version)
 
         return InstallationCandidate(search.supplied, version, link)
@@ -828,7 +836,8 @@ def links(self):
                 url = self.clean_link(
                     urllib_parse.urljoin(self.base_url, href)
                 )
-                yield Link(url, self)
+                pyrequire = anchor.get('data-requires-python')
+                yield Link(url, self, requires_python=pyrequire)
 
     _clean_re = re.compile(r'[^a-z0-9$&+,/:;=?@.#%_\\|-]', re.I)
 
@@ -842,18 +851,39 @@ def clean_link(self, url):
 
 class Link(object):
 
-    def __init__(self, url, comes_from=None):
+    def __init__(self, url, comes_from=None, requires_python=None):
+        """
+        Object representing a parsed link from https://pypi.python.org/simple/*
+
+        url:
+            url of the resource pointed to (href of the link)
+        comes_form:
+            <Not sure>
+        requires_python:
+            String containing the `Requires-Python` metadata field, specified
+            in PEP 345. This is to understand pep 503. The `requires_python`
+            string will be unescaped as pep 503 requires `<` and `>` to be
+            escaped, then stored under the `requires_python` attribute.
+        """
 
         # url can be a UNC windows share
         if url.startswith('\\\\'):
             url = path_to_url(url)
 
         self.url = url
         self.comes_from = comes_from
+        if not requires_python:
+            self.requires_python = None
+        else:
+            self.requires_python = unescape(requires_python)
 
     def __str__(self):
+        if self.requires_python:
+            rp = ' (requires-python:%s)' % self.requires_python
+        else:
+            rp = ''
         if self.comes_from:
-            return '%s (from %s)' % (self.url, self.comes_from)
+            return '%s (from %s)%s' % (self.url, self.comes_from, rp)
         else:
             return str(self.url)
 

pip/utils/packaging.py

@@ -0,0 +1,32 @@
+from __future__ import absolute_import
+import logging
+import sys
+
+from pip._vendor.packaging import specifiers
+from pip._vendor.packaging import version
+
+logger = logging.getLogger(__name__)
+
+def check_requires_python(requires_python):
+    """
+    Check if the python version in used match the `requires_python` specifier passed.
+
+    Return `True` if the version of python in use matches the requirement.
+    Return `False` if the version of python in use does not matches the requirement.
+    Raises an InvalidSpecifier if `requires_python` have an invalid format.
+    """
+    if requires_python is None:
+        # The package provides no information
+        return True
+    try:
+        requires_python_specifier = specifiers.SpecifierSet(requires_python)
+    except specifiers.InvalidSpecifier as e:
+        logger.debug(
+            "Package %s has an invalid Requires-Python entry - %s" % (
+                 requires_python, e))
+        raise specifiers.InvalidSpecifier(*e.args)
+
+    # We only use major.minor.micro
+    python_version = version.parse('.'.join(map(str, sys.version_info[:3])))
+    return python_version in requires_python_specifier
+