Merge pull request #531 from pypa/i530

Fix relative imports in __init__.py when exec-ing to get __version__

doc/history.rst

@@ -1,6 +1,12 @@
 Release history
 ===============
 
+Version 3.7.1
+-------------
+
+- Fix building packages which need execution to get the version number,
+  and have a relative import in ``__init__.py`` (:ghpull:`531`).
+
 Version 3.7
 -----------
 

flit_core/flit_core/common.py

@@ -3,6 +3,7 @@
 import hashlib
 import logging
 import os
+import sys
 
 from pathlib import Path
 import re
@@ -168,7 +169,15 @@ def get_docstring_and_version_via_import(target):
     spec = spec_from_file_location(mod_name, target.file)
     with _module_load_ctx():
         m = module_from_spec(spec)
-        spec.loader.exec_module(m)
+        # Add the module to sys.modules to allow relative imports to work.
+        # importlib has more code around this to handle the case where two
+        # threads are trying to load the same module at the same time, but Flit
+        # should always be running a single thread, so we won't duplicate that.
+        sys.modules[mod_name] = m
+        try:
+            spec.loader.exec_module(m)
+        finally:
+            sys.modules.pop(mod_name, None)
 
     docstring = m.__dict__.get('__doc__', None)
     version = m.__dict__.get('__version__', None)

flit_core/flit_core/tests/samples/imported_version/package1/__init__.py

@@ -0,0 +1,3 @@
+"""This module has a __version__ that requires a relative import"""
+
+from ._version import __version__

flit_core/flit_core/tests/samples/imported_version/package1/_version.py

@@ -0,0 +1 @@
+__version__ = '0.5.8'

flit_core/flit_core/tests/samples/imported_version/pyproject.toml

@@ -0,0 +1,10 @@
+[build-system]
+requires = ["flit_core >=3.2,<4"]
+build-backend = "flit_core.buildapi"
+
+[project]
+name = "package1"
+authors = [
+    {name = "Sir Röbin", email = "robin@camelot.uk"}
+]
+dynamic = ["version", "description"]

flit_core/flit_core/tests/test_common.py

@@ -75,6 +75,11 @@ def test_get_info_from_module(self):
                                 'version': '1.2.3'}
                          )
 
+        info = get_info_from_module(Module('package1', samples_dir / 'imported_version'))
+        self.assertEqual(info, {'summary': 'This module has a __version__ that requires a relative import',
+                                'version': '0.5.8'}
+                         )
+
         with self.assertRaises(InvalidVersion):
             get_info_from_module(Module('invalid_version1', samples_dir))