René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[WASI] test cases with sys.path.insert(0, os.curdir) fail on WASI","articleBody":"**Bug report**\r\n\r\nTest cases that insert ``os.curdir`` (``'.'``) into ``sys.path`` fail on WASI platforms. I think it is related how wasmtime maps directories into the runtime environment and how it sets up the current working directory. The test passes if I replace ``'.'`` with an empty string ``''`` or remove the cached ``FileFinder`` instance for ``'.'`` with ``sys.path_importer_cache.pop('.')``.\r\n\r\n```\r\n ./test-wasi.sh test_support -m test_forget\r\n0:00:00 Run tests sequentially\r\n0:00:00 [1/1] test_support\r\ntest test_support failed -- Traceback (most recent call last):\r\n  File \"/Lib/test/test_support.py\", line 116, in test_forget\r\n    mod = __import__(TESTFN)\r\n          ^^^^^^^^^^^^^^^^^^\r\nModuleNotFoundError: No module named '@test_66600_tmpæ'\r\n\r\ntest_support failed (1 error)\r\n\r\n== Tests result: FAILURE ==\r\n```\r\n\r\nThe culprit seems to be an outdated ``FileFinder`` instance: ``{'.': FileFinder('/.')}``. The CWD is ``'/python-wasm/cpython/builddir/wasi/build/test_python_66600æ'`` when the test case is executed.\r\n\r\n```\r\n0:00:00 [1/1] test_support\r\n\u003e /Lib/test/test_support.py(114)test_forget()\r\n-\u003e sys.path.insert(0, os.curdir)\r\n(Pdb) p sys.path\r\n['.', '/usr/local/lib/python312.zip', '/Lib', '/build/lib.wasi-wasm32-3.12']\r\n(Pdb) pp sys.path_importer_cache\r\n{'.': FileFinder('/.'),\r\n '/Lib': FileFinder('/Lib'),\r\n '/Lib/collections': FileFinder('/Lib/collections'),\r\n '/Lib/encodings': FileFinder('/Lib/encodings'),\r\n '/Lib/importlib': FileFinder('/Lib/importlib'),\r\n '/Lib/re': FileFinder('/Lib/re'),\r\n '/Lib/test': FileFinder('/Lib/test'),\r\n '/Lib/test/libregrtest': FileFinder('/Lib/test/libregrtest'),\r\n '/Lib/test/support': FileFinder('/Lib/test/support'),\r\n '/Lib/unittest': FileFinder('/Lib/unittest'),\r\n '/Lib/urllib': FileFinder('/Lib/urllib'),\r\n '/build/lib.wasi-wasm32-3.12': FileFinder('/build/lib.wasi-wasm32-3.12'),\r\n '/usr/local/lib/python312.zip': None}\r\n(Pdb) p os.getcwd()\r\n'/python-wasm/cpython/builddir/wasi/build/test_python_66600æ'\r\n(Pdb) n\r\n\u003e /Lib/test/test_support.py(115)test_forget()\r\n-\u003e importlib.invalidate_caches()\r\n(Pdb) n\r\n\u003e /Lib/test/test_support.py(116)test_forget()\r\n-\u003e try:\r\n(Pdb) p sys.path\r\n['.', '.', '/usr/local/lib/python312.zip', '/Lib', '/build/lib.wasi-wasm32-3.12']\r\n(Pdb) pp sys.path_importer_cache\r\n{'.': FileFinder('/.'),\r\n '/Lib': FileFinder('/Lib'),\r\n '/Lib/collections': FileFinder('/Lib/collections'),\r\n '/Lib/encodings': FileFinder('/Lib/encodings'),\r\n '/Lib/importlib': FileFinder('/Lib/importlib'),\r\n '/Lib/re': FileFinder('/Lib/re'),\r\n '/Lib/test': FileFinder('/Lib/test'),\r\n '/Lib/test/libregrtest': FileFinder('/Lib/test/libregrtest'),\r\n '/Lib/test/support': FileFinder('/Lib/test/support'),\r\n '/Lib/unittest': FileFinder('/Lib/unittest'),\r\n '/Lib/urllib': FileFinder('/Lib/urllib'),\r\n '/build/lib.wasi-wasm32-3.12': FileFinder('/build/lib.wasi-wasm32-3.12'),\r\n '/usr/local/lib/python312.zip': None}\r\n```\r\n\r\nA build on Linux has an absolute path to build directory as first ``sys.path`` entry.\r\n\r\n**reproducer**\r\n\r\n```\r\n$ podman run --rm -ti -v $(pwd):/python-wasm/cpython:Z quay.io/tiran/cpythonbuild:emsdk3\r\n# ./build-python-build.sh\r\n# ./build-python-wasi.sh\r\n# ./test-wasi.sh test_support -m test_forget\r\n```","author":{"url":"https://github.com/tiran","@type":"Person","name":"tiran"},"datePublished":"2022-06-03T10:33:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/93461/cpython/issues/93461"}