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.

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/test/test_py_compile.py b/Lib/test/test_py_compile.py
index bcb686c86b..8fc0b3308c 100644
--- a/Lib/test/test_py_compile.py
+++ b/Lib/test/test_py_compile.py
@@ -98,6 +98,18 @@ class PyCompileTests(unittest.TestCase):
         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