Consolidate hash constants in pip.utils.hashing.

pip/cmdoptions.py

@@ -17,6 +17,7 @@ from pip.index import (
     PyPI, FormatControl, fmt_ctl_handle_mutual_exclude, fmt_ctl_no_binary,
     fmt_ctl_no_use_wheel)
 from pip.locations import CA_BUNDLE_PATH, USER_CACHE_DIR, src_prefix
+from pip.utils.hashes import STRONG_HASHES
 
 
 def make_option_group(group, parser):
@@ -523,14 +524,6 @@ always_unzip = partial(
 )
 
 
-def strong_hashes():
-    """Return names of hashlib algorithms allowed by the --hash option.
-
-    Currently, those are the ones at least as collision-resistant as sha256.
-    """
-    return ['sha256', 'sha384', 'sha512']
-
-
 def _merge_hash(option, opt_str, value, parser):
     """Given a value spelled "algo:digest", append the digest to a list
     pointed to in a dict by the algo name."""
@@ -542,10 +535,9 @@ def _merge_hash(option, opt_str, value, parser):
         parser.error('Arguments to %s must be a hash name '
                      'followed by a value, like --hash=sha256:abcde...' %
                      opt_str)
-    strongs = strong_hashes()
-    if algo not in strongs:
+    if algo not in STRONG_HASHES:
         parser.error('Allowed hash algorithms for %s are %s.' %
-                     (opt_str, ', '.join(strongs)))
+                     (opt_str, ', '.join(STRONG_HASHES)))
     parser.values.hashes.setdefault(algo, []).append(digest)
 
 

pip/commands/hash.py

@@ -5,10 +5,9 @@ import logging
 import sys
 
 from pip.basecommand import Command
-from pip.cmdoptions import strong_hashes
-from pip.exceptions import FAVORITE_HASH
 from pip.status_codes import ERROR
 from pip.utils import read_chunks
+from pip.utils.hashes import FAVORITE_HASH, STRONG_HASHES
 
 
 logger = logging.getLogger(__name__)
@@ -31,11 +30,11 @@ class HashCommand(Command):
         self.cmd_opts.add_option(
             '-a', '--algorithm',
             dest='algorithm',
-            choices=strong_hashes(),
+            choices=STRONG_HASHES,
             action='store',
             default=FAVORITE_HASH,
             help='The hash algorithm to use: one of %s' %
-                 ', '.join(strong_hashes()))
+                 ', '.join(STRONG_HASHES))
         self.parser.insert_option_group(0, self.cmd_opts)
 
     def run(self, options, args):

pip/exceptions.py

@@ -51,11 +51,6 @@ class UnsupportedWheel(InstallationError):
     """Unsupported wheel."""
 
 
-# The recommended hash algo of the moment. Change this whenever the state of
-# the art changes; it won't hurt backward compatibility.
-FAVORITE_HASH = 'sha256'
-
-
 class HashErrors(InstallationError):
     """Multiple HashError instances rolled into one for reporting"""
 
@@ -163,6 +158,8 @@ class HashMissing(HashError):
         self.gotten_hash = gotten_hash
 
     def body(self):
+        from pip.utils.hashes import FAVORITE_HASH  # Dodge circular import.
+
         package_name = (self.req.req if self.req and
                         # In case someone feeds something
                         # downright stupid to

pip/utils/hashes.py

@@ -2,12 +2,21 @@ from __future__ import absolute_import
 
 import hashlib
 
-from pip.exceptions import (HashMismatch, HashMissing, InstallationError,
-                            FAVORITE_HASH)
+from pip.exceptions import HashMismatch, HashMissing, InstallationError
 from pip.utils import read_chunks
 from pip._vendor.six import iteritems, iterkeys, itervalues
 
 
+# The recommended hash algo of the moment. Change this whenever the state of
+# the art changes; it won't hurt backward compatibility.
+FAVORITE_HASH = 'sha256'
+
+
+# Names of hashlib algorithms allowed by the --hash option and ``pip hash``
+# Currently, those are the ones at least as collision-resistant as sha256.
+STRONG_HASHES = ['sha256', 'sha384', 'sha512']
+
+
 class Hashes(object):
     """A wrapper that builds multiple hashes at once and checks them against
     known-good values