Simplify and clarify resolver platform expansion.

pex/resolver.py

@@ -165,52 +165,57 @@ class Resolver(object):
   class Error(Exception): pass
 
   @staticmethod
-  def _expand_and_maybe_adjust_platform(interpreter, platform=None):
-    # Adjusts `platform` if it is 'current' and does not match the given `interpreter` platform.
-    cur_plat = Platform.current()
-
-    given_platform = Platform.create(platform or 'current')
-    if cur_plat.platform != given_platform.platform:
-      # IE: Say we're on OSX and platform was 'linux-x86_64' or 'linux_x86_64-cp-27-cp27mu'.
-      return given_platform
-
-    if (interpreter.identity.abbr_impl,
-        interpreter.identity.impl_ver,
-        interpreter.identity.abi_tag) == (cur_plat.impl, cur_plat.version, cur_plat.abi):
-      # IE: Say we're on Linux and platform was 'current' or 'linux-x86_64' or
-      # 'linux_x86_64-cp-27-cp27mu'and the current extended platform info matches the given
-      # interpreter exactly.
-      return cur_plat
-
-    # Otherwise we need to adjust the platform to match a local interpreter different from the
-    # currently executing interpreter.
-    adjusted_platform = Platform(platform=cur_plat.platform,
-                                 impl=interpreter.identity.abbr_impl,
-                                 version=interpreter.identity.impl_ver,
-                                 abi=interpreter.identity.abi_tag)
-
-    TRACER.log("""
-  Modifying given platform of {given_platform!r}:
-  Using the current platform of {current_platform!r}
-  Under current interpreter {current_interpreter!r}
-
-  To match given interpreter {given_interpreter!r}.
-
-  Calculated platform: {calculated_platform!r}""".format(
-      given_platform=given_platform,
-      current_platform=cur_plat,
-      current_interpreter=PythonInterpreter.get(),
-      given_interpreter=interpreter,
-      calculated_platform=adjusted_platform),
-      V=9
-    )
+  def _maybe_expand_platform(interpreter, platform=None):
+    # Expands `platform` if it is 'current' and abbreviated.
+    #
+    # IE: If we're on linux and handed a platform of `None`, 'current', or 'linux_x86_64', we expand
+    # the platform to an extended platform matching the given interpreter's abi info, eg:
+    # 'linux_x86_64-cp-27-cp27mu'.
 
-    return adjusted_platform
+    cur_plat = Platform.current()
+    def expand_platform():
+      expanded_platform = Platform(platform=cur_plat.platform,
+                                   impl=interpreter.identity.abbr_impl,
+                                   version=interpreter.identity.impl_ver,
+                                   abi=interpreter.identity.abi_tag)
+      TRACER.log("""
+Modifying given platform of {given_platform!r}:
+Using the current platform of {current_platform!r}
+Under current interpreter {current_interpreter!r}
+
+To match given interpreter {given_interpreter!r}.
+
+Calculated platform: {calculated_platform!r}""".format(
+        given_platform=platform,
+        current_platform=cur_plat,
+        current_interpreter=PythonInterpreter.get(),
+        given_interpreter=interpreter,
+        calculated_platform=expanded_platform),
+        V=9
+      )
+      return expanded_platform
+
+    if platform in (None, 'current'):
+      # Always expand the default local (abbreviated) platform to the given interpreter.
+      return expand_platform()
+    else:
+      given_platform = Platform.create(platform)
+      if given_platform.is_extended:
+        # Always respect an explicit extended platform.
+        return given_platform
+      elif given_platform.platform != cur_plat.platform:
+        # IE: Say we're on OSX and platform was 'linux-x86_64'; we can't expand a non-local
+        # platform so we leave as-is.
+        return given_platform
+      else:
+        # IE: Say we're on 64 bit linux and platform was 'linux-x86_64'; ie: the abbreviated local
+        # platform.
+        return expand_platform()
 
   def __init__(self, allow_prereleases=None, interpreter=None, platform=None,
                pkg_blacklist=None, use_manylinux=None):
     self._interpreter = interpreter or PythonInterpreter.get()
-    self._platform = self._expand_and_maybe_adjust_platform(self._interpreter, platform)
+    self._platform = self._maybe_expand_platform(self._interpreter, platform)
     self._allow_prereleases = allow_prereleases
     self._blacklist = pkg_blacklist.copy() if pkg_blacklist else {}
     self._supported_tags = self._platform.supported_tags(

tests/test_environment.py

@@ -9,7 +9,7 @@
 from twitter.common.contextutil import temporary_dir
 
 from pex import resolver
-from pex.compatibility import nested
+from pex.compatibility import nested, to_bytes
 from pex.environment import PEXEnvironment
 from pex.installer import EggInstaller, WheelInstaller
 from pex.interpreter import PythonInterpreter
@@ -161,4 +161,4 @@ def bad_interpreter(include_site_extras=True):
       # Verify this all worked under the previously problematic pkg_resources-reported platform.
       release, _, _ = platform.mac_ver()
       major_minor = '.'.join(release.split('.')[:2])
-      assert b'macosx-{}-intel'.format(major_minor) == stdout.strip()
+      assert to_bytes('macosx-{}-intel'.format(major_minor)) == stdout.strip()