refactor(tests): replace exec() with importlib in example runner

cuda_core/tests/example_tests/test_basic_examples.py

@@ -3,21 +3,22 @@
 
 # If we have subcategories of examples in the future, this file can be split along those lines
 
-import glob
-import os
+from pathlib import Path
 
 import pytest
-from cuda.core import Device
 
 from .utils import run_example
 
-samples_path = os.path.join(os.path.dirname(__file__), "..", "..", "examples")
-sample_files = glob.glob(samples_path + "**/*.py", recursive=True)
+# not dividing, but navigating into the "examples" directory.
+EXAMPLES_DIR = Path(__file__).resolve().parent.parent.parent / "examples"
 
+# recursively glob for test files in examples directory, sort for deterministic
+# test runs. Relative paths offer cleaner output when tests fail.
+SAMPLE_FILES = sorted([str(p.relative_to(EXAMPLES_DIR)) for p in EXAMPLES_DIR.glob("**/*.py")])
 
-@pytest.mark.parametrize("example", sample_files)
+
+@pytest.mark.parametrize("example_rel_path", SAMPLE_FILES)
 class TestExamples:
-    def test_example(self, example, deinit_cuda):
-        run_example(samples_path, example)
-        if Device().device_id != 0:
-            Device(0).set_current()
+    # deinit_cuda is defined in conftest.py and pops the cuda context automatically.
+    def test_example(self, example_rel_path: str, deinit_cuda) -> None:
+        run_example(str(EXAMPLES_DIR), example_rel_path)

cuda_core/tests/example_tests/utils.py

@@ -2,8 +2,9 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import gc
-import os
+import importlib.util
 import sys
+from pathlib import Path
 
 import pytest
 
@@ -12,24 +13,38 @@ class SampleTestError(Exception):
     pass
 
 
-def parse_python_script(filepath):
-    if not filepath.endswith(".py"):
-        raise ValueError(f"{filepath} not supported")
-    with open(filepath, encoding="utf-8") as f:
-        script = f.read()
-    return script
+def run_example(parent_dir: str, rel_path_to_example: str, env=None) -> None:
+    fullpath = Path(parent_dir) / rel_path_to_example
+    module_name = fullpath.stem
 
+    old_sys_path = sys.path.copy()
+    old_argv = sys.argv
 
-def run_example(samples_path, filename, env=None):
-    fullpath = os.path.join(samples_path, filename)
-    script = parse_python_script(fullpath)
     try:
-        old_argv = sys.argv
-        sys.argv = [fullpath]
-        old_sys_path = sys.path.copy()
-        sys.path.append(samples_path)
-        # TODO: Refactor the examples to give them a common callable `main()` to avoid needing to use exec here?
-        exec(script, env if env else {})  # noqa: S102
+        sys.path.append(parent_dir)
+        sys.argv = [str(fullpath)]
+
+        # Collect metadata for file 'module_name' located at 'fullpath'.
+        # CASE: file does not exist -> spec is none.
+        # CASE: file is not .py -> spec is none.
+        # CASE: file does not have proper loader (module.spec.__loader__) -> spec.loader is none.
+        spec = importlib.util.spec_from_file_location(module_name, fullpath)
+
+        if spec is None or spec.loader is None:
+            raise ImportError(f"Failed to load spec for {rel_path_to_example}")
+
+        # Otherwise convert the spec to a module, then run the module.
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[module_name] = module
+
+        # This runs top-level code.
+        # CASE: exec() -> top-level code is implicitly run.
+        spec.loader.exec_module(module)
+
+        # CASE: main() -> we find main and call it below.
+        if hasattr(module, "main"):
+            module.main()
+
     except ImportError as e:
         # for samples requiring any of optional dependencies
         for m in ("cupy", "torch"):
@@ -40,14 +55,16 @@ def run_example(samples_path, filename, env=None):
             raise
     except SystemExit:
         # for samples that early return due to any missing requirements
-        pytest.skip(f"skip {filename}")
+        pytest.skip(f"skip {rel_path_to_example}")
     except Exception as e:
         msg = "\n"
-        msg += f"Got error ({filename}):\n"
+        msg += f"Got error ({rel_path_to_example}):\n"
         msg += str(e)
         raise SampleTestError(msg) from e
     finally:
         sys.path = old_sys_path
         sys.argv = old_argv
+
         # further reduce the memory watermark
+        sys.modules.pop(module_name, None)
         gc.collect()