[feat] Support relative imports in tests

docs/manpage.rst

@@ -27,7 +27,7 @@ Test discovery and test loading
 This is the very first phase of the frontend.
 ReFrame will search for tests in its *check search path* and will load them.
 When ReFrame loads a test, it actually *instantiates* it, meaning that it will call its :func:`__init__` method unconditionally whether this test is meant to run on the selected system or not.
-This is something that writers of regression tests should bear in mind.
+This is something that test developers should bear in mind.
 
 .. option:: -c, --checkpath=PATH
 
@@ -45,6 +45,14 @@ This is something that writers of regression tests should bear in mind.
 
    This option can also be set using the :envvar:`RFM_CHECK_SEARCH_RECURSIVE` environment variable or the :attr:`~config.general.check_search_recursive` general configuration parameter.
 
+.. note::
+   ReFrame will fail to load a test with a relative import unless *any* of the following holds true:
+
+   1. The test is located under ReFrame's installation prefix.
+   2. The parent directory of the test contains an ``__init__.py`` file.
+
+   For versions prior to 4.6, relative imports are supported only for case (1).
+
 
 .. _test-filtering:
 

reframe/frontend/loader.py

@@ -195,8 +195,15 @@ def load_from_file(self, filename, force=False):
             dirname = os.path.dirname(filename)
             with osext.change_dir(dirname):
                 with util.temp_sys_path(dirname):
+                    if os.path.exists(os.path.join(dirname, '__init__.py')):
+                        # If the containing directory is a package,
+                        # import it, too.
+                        parent = util.import_module_from_file(dirname).__name__
+                    else:
+                        parent = None
+
                     return self.load_from_module(
-                        util.import_module_from_file(filename, force)
+                        util.import_module_from_file(filename, force, parent)
                     )
         except Exception:
             exc_info = sys.exc_info()

reframe/utility/__init__.py

@@ -70,7 +70,7 @@ def _do_import_module_from_file(filename, module_name=None):
     return module
 
 
-def import_module_from_file(filename, force=False):
+def import_module_from_file(filename, force=False, parent=None):
     '''Import module from file.
 
     If the file location refers to a directory, the contained ``__init__.py``
@@ -85,7 +85,14 @@ def import_module_from_file(filename, force=False):
 
     :arg filename: The path to the filename of a Python module.
     :arg force: Force reload of module in case it is already loaded.
+    :arg parent: The name of the parent module of the one that will be loaded.
+        This will essentially prefix the module of the newly loaded module with
+        ``parent`` so that Python would be able to resolve relative imports in
+        the module file.
     :returns: The loaded Python module.
+
+    .. versionchanged:: 4.6
+       The ``parent`` argument is added.
     '''
 
     # Expand and sanitize filename
@@ -103,6 +110,9 @@ def import_module_from_file(filename, force=False):
         # with other modules loaded with a standard `import` or with multiple
         # test files with the same name that reside in different directories.
         module_hash = sha256(filename.encode('utf-8')).hexdigest()[:8]
+        if parent:
+            module_name = f'{parent}.{module_name}'
+
         module_name = f'{module_name}@{module_hash}'
         return _do_import_module_from_file(filename, module_name)
 

unittests/resources/checks_unlisted/testlib/simple.py

@@ -5,21 +5,17 @@
 
 import reframe as rfm
 import reframe.utility.sanity as sn
-
-
-class dummy_fixture(rfm.RunOnlyRegressionTest, pin_prefix=True):
-    executable = 'echo'
-    sanity_patterns = sn.assert_true(1)
+from .utility import dummy_fixture
 
 
 @rfm.simple_test
-class simple_echo_check(rfm.RunOnlyRegressionTest):
+class simple_echo_check(rfm.RunOnlyRegressionTest, pin_prefix=True):
     descr = 'Simple Echo Test'
     valid_systems = ['*']
     valid_prog_environs = ['builtin']
     executable = 'echo'
     executable_opts = ['Hello']
-    message = variable(str, value='World') 
+    message = variable(str, value='World')
     dummy = fixture(dummy_fixture, scope='environment')
 
     @run_before('run')

unittests/resources/checks_unlisted/testlib/utility/__init__.py

@@ -0,0 +1,7 @@
+import reframe as rfm
+import reframe.utility.sanity as sn
+
+
+class dummy_fixture(rfm.RunOnlyRegressionTest):
+    executable = 'echo'
+    sanity_patterns = sn.assert_true(1)

unittests/resources/checks_unlisted/testlib_inheritance_foo.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 import reframe as rfm
-
 from testlib.simple import simple_echo_check
 
 

unittests/test_loader.py

@@ -8,6 +8,7 @@
 import shutil
 
 import reframe as rfm
+import reframe.utility.osext as osext
 from reframe.core.exceptions import ReframeSyntaxError
 from reframe.frontend.loader import RegressionCheckLoader
 
@@ -140,3 +141,16 @@ def setup(self, partition, environ, **job_opts):
         class TestSpecialDerived(TestSpecial):
             def setup(self, partition, environ, **job_opts):
                 super().setup(partition, environ, **job_opts)
+
+
+def test_relative_import_outside_rfm_prefix(loader, tmp_path):
+    # If a test file resides under the reframe installation prefix, it will be
+    # imported as a hierarchical module. If not, we want to make sure that
+    # reframe will still load its parent modules
+
+    osext.copytree(
+        os.path.abspath('unittests/resources/checks_unlisted/testlib'),
+        tmp_path / 'testlib', dirs_exist_ok=True
+    )
+    tests = loader.load_from_file(str(tmp_path / 'testlib' / 'simple.py'))
+    assert len(tests) == 2