hash_reqs: Include python version when generating hash.

Fixes #12868.
We now also include python version in the format
'major.minor.patchlevel', when generating hash for a
requirement file. This was necessary since packages tend to
break on different versions of python, so it is important to
track the version on which the venv was setup.

WARN: This commit will force all zulip venvs to be recreated.

scripts/lib/hash_reqs.py

@@ -2,8 +2,9 @@
 import argparse
 import hashlib
 import os
+import subprocess
 import sys
-from typing import Iterable, List, MutableSet
+from typing import Iterable, List
 
 
 def expand_reqs_helper(fpath: str) -> List[str]:
@@ -27,8 +28,14 @@ def expand_reqs(fpath: str) -> List[str]:
     output = expand_reqs_helper(absfpath)
     return sorted(set(output))
 
+def python_version() -> str:
+    """
+    Returns the Python version as string 'Python major.minor.patchlevel'
+    """
+    return subprocess.check_output(["/usr/bin/python3", "-VV"], universal_newlines=True)
+
 def hash_deps(deps: Iterable[str]) -> str:
-    deps_str = "\n".join(deps) + "\n"
+    deps_str = "\n".join(deps) + "\n" + python_version()
     return hashlib.sha1(deps_str.encode('utf-8')).hexdigest()
 
 def main() -> int:

scripts/lib/setup_venv.py

@@ -262,16 +262,19 @@ def do_patch_activate_script(venv_path: str) -> None:
     with open(script_path, 'w') as f:
         f.write("".join(lines))
 
+def generate_hash(requirements_file: str) -> str:
+    path = os.path.join(ZULIP_PATH, 'scripts', 'lib', 'hash_reqs.py')
+    output = subprocess.check_output([path, requirements_file], universal_newlines=True)
+    return output.split()[0]
+
 def setup_virtualenv(
     target_venv_path: Optional[str],
     requirements_file: str,
     patch_activate_script: bool = False,
 ) -> str:
 
+    sha1sum = generate_hash(requirements_file)
     # Check if a cached version already exists
-    path = os.path.join(ZULIP_PATH, 'scripts', 'lib', 'hash_reqs.py')
-    output = subprocess.check_output([path, requirements_file], universal_newlines=True)
-    sha1sum = output.split()[0]
     if target_venv_path is None:
         cached_venv_path = os.path.join(VENV_CACHE_PATH, sha1sum, 'venv')
     else:

tools/tests/test_hash_reqs.py

@@ -0,0 +1,25 @@
+import unittest
+
+import mock
+
+from scripts.lib.hash_reqs import expand_reqs, hash_deps
+from tools.setup.setup_venvs import DEV_REQS_FILE
+
+
+class TestHashCreation(unittest.TestCase):
+
+    def test_diff_hash_for_diff_python_version(self) -> None:
+        with mock.patch('scripts.lib.hash_reqs.python_version', return_value='Python 3.6.9'):
+            deps = expand_reqs(DEV_REQS_FILE)
+            hash1 = hash_deps(deps)
+
+        with mock.patch('scripts.lib.hash_reqs.python_version', return_value='Python 3.6.9'):
+            deps = expand_reqs(DEV_REQS_FILE)
+            hash2 = hash_deps(deps)
+
+        with mock.patch('scripts.lib.hash_reqs.python_version', return_value='Python 3.8.2'):
+            deps = expand_reqs(DEV_REQS_FILE)
+            hash3 = hash_deps(deps)
+
+        assert hash1 == hash2
+        assert hash1 != hash3