Fix importing module from python file

reframe/utility/__init__.py

@@ -14,11 +14,13 @@ def _get_module_name(filename):
         barename = os.path.dirname(filename)
 
     if os.path.isabs(barename):
-        module_name = os.path.basename(barename)
-    else:
-        module_name = barename.replace(os.sep, '.')
+        raise AssertionError('BUG: _get_module_name() '
+                             'accepts relative paths only')
 
-    return module_name
+    if filename.startswith('..'):
+        return os.path.basename(barename)
+    else:
+        return barename.replace(os.sep, '.')
 
 
 def _do_import_module_from_file(filename, module_name=None):
@@ -40,15 +42,17 @@ def _do_import_module_from_file(filename, module_name=None):
 def import_module_from_file(filename):
     """Import module from file."""
 
-    filename = os.path.normpath(os.path.expandvars(filename))
+    # Expand and sanitize filename
+    filename = os.path.abspath(os.path.expandvars(filename))
     if os.path.isdir(filename):
         filename = os.path.join(filename, '__init__.py')
 
-    if filename.startswith('..'):
-        filename = os.path.abspath(filename)
-
-    module_name = _get_module_name(filename)
-    if os.path.isabs(filename):
+    # Express filename relative to reframe
+    rel_filename = os.path.relpath(filename, sys.path[0])
+    module_name = _get_module_name(rel_filename)
+    if rel_filename.startswith('..'):
+        # We cannot use the standard Python import mechanism here, because the
+        # module to import is outside the top-level package
         return _do_import_module_from_file(filename, module_name)
 
     return importlib.import_module(module_name)

unittests/test_utility.py

@@ -287,15 +287,31 @@ def test_load_directory_relative(self):
             self.assertEqual('reframe', module.__name__)
             self.assertIs(module, sys.modules.get('reframe'))
 
-    def test_load_file_relative(self):
+    def test_load_relative(self):
         with os_ext.change_dir('reframe'):
+            # Load a module from a directory up
             module = util.import_module_from_file('../reframe/__init__.py')
             self.assertEqual(reframe.VERSION, module.VERSION)
             self.assertEqual('reframe', module.__name__)
             self.assertIs(module, sys.modules.get('reframe'))
 
+            # Load a module from the current directory
+            module = util.import_module_from_file('utility/os_ext.py')
+            self.assertEqual('reframe.utility.os_ext', module.__name__)
+            self.assertIs(module, sys.modules.get('reframe.utility.os_ext'))
+
+    def test_load_outside_pkg(self):
+        module = util.import_module_from_file(os.path.__file__)
+
+        # os imports the OS-specific path libraries under the name `path`. Our
+        # importer will import the actual file, thus the module name should be
+        # the real one.
+        self.assertTrue(module is sys.modules.get('posixpath') or
+                        module is sys.modules.get('ntpath') or
+                        module is sys.modules.get('macpath'))
+
     def test_load_twice(self):
-        filename = os.path.abspath('reframe/__init__.py')
+        filename = os.path.abspath('reframe')
         module1 = util.import_module_from_file(filename)
         module2 = util.import_module_from_file(filename)
         self.assertIs(module1, module2)