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bpo-29708: Setting SOURCE_DATE_EPOCH forces hash-based .pyc files (GH…

…-5200)

To support reproducible builds, the setting of of SOURCE_DATE_EPOCH triggers the py_compile module -- and by extension, compileall -- to forcibly compile with hash-based .pyc files. This eliminates the possibility of timestamp-based .pyc files which vary between builds.
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bmwiedemann authored and brettcannon committed Jan 24, 2018
1 parent 6f6eb35 commit ccbe5818af20f8c12043f5c30c277a74714405e0
@@ -55,7 +55,9 @@ byte-code cache files in the directory containing the source code.
*invalidation_mode* should be a member of the :class:`PycInvalidationMode`
enum and controls how the generated ``.pyc`` files are invalidated at
runtime.
runtime. If the :envvar:`SOURCE_DATE_EPOCH` environment variable is set,
*invalidation_mode* will be forced to
:attr:`PycInvalidationMode.CHECKED_HASH`.
.. versionchanged:: 3.2
Changed default value of *cfile* to be :PEP:`3147`-compliant. Previous
@@ -71,6 +73,9 @@ byte-code cache files in the directory containing the source code.
.. versionchanged:: 3.7
The *invalidation_mode* parameter was added as specified in :pep:`552`.
If the :envvar:`SOURCE_DATE_EPOCH` environment variable is set,
*invalidation_mode* will be forced to
:attr:`PycInvalidationMode.CHECKED_HASH`.
.. class:: PycInvalidationMode
View
@@ -112,6 +112,8 @@ def compile(file, cfile=None, dfile=None, doraise=False, optimize=-1,
the resulting file would be regular and thus not the same type of file as
it was previously.
"""
if os.environ.get('SOURCE_DATE_EPOCH'):
invalidation_mode = PycInvalidationMode.CHECKED_HASH
if cfile is None:
if optimize >= 0:
optimization = optimize if optimize >= 1 else ''
@@ -98,6 +98,18 @@ def test_bad_coding(self):
self.assertFalse(os.path.exists(
importlib.util.cache_from_source(bad_coding)))
def test_source_date_epoch(self):
testtime = 123456789
with support.EnvironmentVarGuard() as env:
env["SOURCE_DATE_EPOCH"] = str(testtime)
py_compile.compile(self.source_path, self.pyc_path)
self.assertTrue(os.path.exists(self.pyc_path))
self.assertFalse(os.path.exists(self.cache_path))
with open(self.pyc_path, 'rb') as fp:
flags = importlib._bootstrap_external._classify_pyc(
fp.read(), 'test', {})
self.assertEqual(flags, 0b11)
@unittest.skipIf(sys.flags.optimize > 0, 'test does not work with -O')
def test_double_dot_no_clobber(self):
# http://bugs.python.org/issue22966
@@ -0,0 +1,2 @@
If the :envvar:`SOURCE_DATE_EPOCH` environment variable is set,
:mod:`py_compile` will always create hash-based ``.pyc`` files.

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