Add SHA256 hash of .whl as info output (#5908)

* Add SHA256 hash of .whl as info output

Currently I'm trying to debug some issues with what appear to be
corrupt wheels.  It would be very useful to see what pip thought the
state of things was as it wrote the wheel output; if a final corrupt
distributed file is then different to what pip has saved in its build
logs, you know the problem is somewhere after pip but before
distribution.

Currently we get a log of the initial creation, then the stamp when it
gets moved in the final output location, e.g.:

 creating '/tmp/pip-wheel-71CpBe/foo-1.2.3-py2.py3-none-any.whl
 ...
 Stored in directory: /opt/wheel/workspace

A lot happens in between this, so my suggestion is we add the final
output file and it's hash before the "Stored in directory:", e.g. you
now see:

 Building wheels for collected packages: simple
   Running setup.py bdist_wheel for simple: started
   Running setup.py bdist_wheel for simple: finished with status 'done'
   Finished: simple-3.0-py3-none-any.whl sha256=39005a57a6327972575072af82e11d0817439fe6a069381f6f2a123a8c0bf1cf
   Stored in directory: /tmp/pytest-of-iwienand/pytest-18/test_pip_wheel_success0/workspace/scratch
 Successfully built simple

Despite the hash being fairly important for things like
--require-hashes, AFAICS the final hash is not put in the logs at all
currently, so I think this is generically helpful.

* Reword wheel hash details output

This rewords the output to be more like the form of the preceding
messages.  Additionally the size is added, since we have calculated it
anyway.  The output will now look like:

 Collecting simple==3.0
 Building wheels for collected packages: simple
   Building wheel for simple (setup.py): started
   Building wheel for simple (setup.py): finished with status 'done'
   Created wheel for simple: filename=simple-3.0-py3-none-any.whl size=1138 sha256=2a980a802c9d38a24d29aded2dc2df2b080e58370902e5fdf950090ff67aec10
   Stored in directory: /tmp/pytest-of-iwienand/pytest-0/test_pip_wheel_success0/workspace/scratch
 Successfully built simple

news/5908.feature

@@ -0,0 +1,2 @@
+Log the final filename and SHA256 of a ``.whl`` file when done building a
+wheel.

src/pip/_internal/wheel.py

@@ -68,15 +68,22 @@ def normpath(src, p):
     return os.path.relpath(src, p).replace(os.path.sep, '/')
 
 
-def rehash(path, blocksize=1 << 20):
-    # type: (str, int) -> Tuple[str, str]
+def hash_file(path, blocksize=1 << 20):
+    # type: (str, int) -> Tuple[Any, int]
     """Return (hash, length) for path using hashlib.sha256()"""
     h = hashlib.sha256()
     length = 0
     with open(path, 'rb') as f:
         for block in read_chunks(f, size=blocksize):
             length += len(block)
             h.update(block)
+    return (h, length)  # type: ignore
+
+
+def rehash(path, blocksize=1 << 20):
+    # type: (str, int) -> Tuple[str, str]
+    """Return (encoded_digest, length) for path using hashlib.sha256()"""
+    h, length = hash_file(path, blocksize)
     digest = 'sha256=' + urlsafe_b64encode(
         h.digest()
     ).decode('latin1').rstrip('=')
@@ -902,7 +909,12 @@ def _build_one_inside_env(self, req, output_dir, python_tag=None):
                 wheel_name = os.path.basename(wheel_path)
                 dest_path = os.path.join(output_dir, wheel_name)
                 try:
+                    wheel_hash, length = hash_file(wheel_path)
                     shutil.move(wheel_path, dest_path)
+                    logger.info('Created wheel for %s: '
+                                'filename=%s size=%d sha256=%s',
+                                req.name, wheel_name, length,
+                                wheel_hash.hexdigest())
                     logger.info('Stored in directory: %s', output_dir)
                     return dest_path
                 except Exception:

tests/functional/test_wheel.py

@@ -1,5 +1,6 @@
 """'pip wheel' tests"""
 import os
+import re
 from os.path import exists
 
 import pytest
@@ -48,6 +49,12 @@ def test_pip_wheel_success(script, data):
     )
     wheel_file_name = 'simple-3.0-py%s-none-any.whl' % pyversion[0]
     wheel_file_path = script.scratch / wheel_file_name
+    assert re.search(
+        r"Created wheel for simple: "
+        r"filename=%s size=\d+ sha256=[A-Fa-f0-9]{64}"
+        % re.escape(wheel_file_name), result.stdout)
+    assert re.search(
+        r"^\s+Stored in directory: ", result.stdout, re.M)
     assert wheel_file_path in result.files_created, result.stdout
     assert "Successfully built simple" in result.stdout, result.stdout
 

tests/unit/test_wheel.py

@@ -815,3 +815,29 @@ def test_missing_PATH_env_treated_as_empty_PATH_env(self):
             retval_empty = wheel.message_about_scripts_not_on_PATH(scripts)
 
         assert retval_missing == retval_empty
+
+
+class TestWheelHashCalculators(object):
+
+    def prep(self, tmpdir):
+        self.test_file = tmpdir.join("hash.file")
+        # Want this big enough to trigger the internal read loops.
+        self.test_file_len = 2 * 1024 * 1024
+        with open(str(self.test_file), "w") as fp:
+            fp.truncate(self.test_file_len)
+        self.test_file_hash = \
+            '5647f05ec18958947d32874eeb788fa396a05d0bab7c1b71f112ceb7e9b31eee'
+        self.test_file_hash_encoded = \
+            'sha256=VkfwXsGJWJR9ModO63iPo5agXQurfBtx8RLOt-mzHu4'
+
+    def test_hash_file(self, tmpdir):
+        self.prep(tmpdir)
+        h, length = wheel.hash_file(self.test_file)
+        assert length == self.test_file_len
+        assert h.hexdigest() == self.test_file_hash
+
+    def test_rehash(self, tmpdir):
+        self.prep(tmpdir)
+        h, length = wheel.rehash(self.test_file)
+        assert length == str(self.test_file_len)
+        assert h == self.test_file_hash_encoded