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+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+"""Unit tests for the runtime search path filter packaging applies to shipped libraries.
+
+Here rather than in the wheel checks, because the decision under test is a pure function of one
+string. The wheel checks can only see it after a full wheel build, and only on the platform that
+built one, so a filter that dropped the wrong entry reached the published artifact before anything
+ran that would notice.
+
+Two properties are covered, and they pull in opposite directions, which is why both are needed.
+The filter must drop the MKL arch directories torch's exported link interface leaves anchored at
+the filesystem root, and it must keep the absolute torch directory that is a library's only route
+to torch when no relative one was recorded. A filter that satisfies either alone is wrong: the
+first way ships unusable paths, the second way stops the extensions importing.
+
+The functions are read out of setup.py rather than restated, so the test exercises what ships.
+setup.py calls setup() at module scope, so it is loaded by compiling the definitions this needs
+instead of importing it, which would exit during setuptools argument parsing.
+"""
+
+import ast
+import importlib.util
+import re
+from pathlib import Path, PurePosixPath
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[3]
+
+# Compiled from setup.py, so a change to the filter is exercised here rather than duplicated.
+_WANTED = (
+    "_MKL_ARCH_DIRECTORIES",
+    "_is_cuda_toolkit_directory",
+    "_is_unresolved_math_library_directory",
+    "_is_usable_runtime_path",
+)
+
+
+def _setup_source() -> str:
+    """setup.py's text, decoded as UTF-8.
+
+    The encoding is named because `read_text()` defaults to the locale's, and both files this test
+    parses contain non-ASCII characters. On a Windows runner that resolves to a code page, which
+    mangles them, and the mangled text is what gets parsed.
+    """
+    return (REPO_ROOT / "setup.py").read_text(encoding="utf-8")
+
+
+def _setup_namespace() -> dict:
+    """The runtime path helpers from setup.py, compiled without running setup()."""
+    tree = ast.parse(_setup_source())
+    wanted = []
+    for node in tree.body:
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+            if node.name in _WANTED:
+                wanted.append(node)
+        elif isinstance(node, ast.Assign):
+            names = [t.id for t in node.targets if isinstance(t, ast.Name)]
+            if any(name in _WANTED for name in names):
+                wanted.append(node)
+    found = set()
+    for node in wanted:
+        found.add(
+            node.name
+            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+            else next(t.id for t in node.targets if isinstance(t, ast.Name))
+        )
+    missing = sorted(set(_WANTED) - found)
+    assert not missing, (
+        f"setup.py no longer defines {missing} at module scope, so this test would silently "
+        "check nothing. Update the names here to match."
+    )
+    namespace = {"re": re, "PurePosixPath": PurePosixPath}
+    exec(
+        compile(ast.Module(body=wanted, type_ignores=[]), "<setup.py>", "exec"),
+        namespace,
+    )
+    return namespace
+
+
+@pytest.fixture(scope="module")
+def setup_helpers() -> dict:
+    return _setup_namespace()
+
+
+# setup.py's own arch names, read at import so the parametrized cases below are driven by the
+# shipped constant rather than a second copy of it. Adding an arch to setup.py then extends both
+# the reject and the accept cases, which is what keeps packaging and the release check in step.
+_MKL_ARCH_DIRECTORIES = _setup_namespace()["_MKL_ARCH_DIRECTORIES"]
+
+# What the linker records when MKL's prefix resolves empty, leaving its arch subdirectory
+# concatenated onto nothing. Two of the three name a Windows layout, in a Linux wheel.
+UNRESOLVED_MATH_DIRECTORIES = tuple(f"/lib/{arch}" for arch in _MKL_ARCH_DIRECTORIES)
+
+
+@pytest.mark.parametrize("entry", UNRESOLVED_MATH_DIRECTORIES)
+def test_drops_math_directories_with_an_empty_prefix(entry, setup_helpers):
+    assert setup_helpers["_is_unresolved_math_library_directory"](entry) is True
+    # A trailing separator is the same directory, which the path type normalises on its own. Asserted
+    # because patchelf prints entries as recorded, so that spelling can genuinely arrive.
+    assert setup_helpers["_is_unresolved_math_library_directory"](entry + "/") is True
+
+
+@pytest.mark.parametrize(
+    "entry",
+    [
+        # A real MKL installation spells the same arch directory below a prefix, and that
+        # directory genuinely exists, so dropping it would break a library resolving through it.
+        "/opt/intel/mkl/lib/intel64",
+        "/opt/intel/oneapi/mkl/latest/lib/intel64",
+        "/usr/lib/intel64",
+        "/home/user/lib/intel64",
+        # The arch name as a parent rather than as the entry itself.
+        "/lib/intel64/extra",
+        # Ordinary system directories, which differ from the bad entries only in the last part.
+        "/lib",
+        "/lib64",
+        "/lib/x86_64-linux-gnu",
+        # Relative entries are decided before this predicate is reached, but it must not claim
+        # one, or a wheel's own hop into a directory named intel64 would be dropped.
+        "$ORIGIN/../../lib",
+        "$ORIGIN/lib/intel64",
+    ],
+)
+def test_keeps_directories_that_name_a_real_prefix(entry, setup_helpers):
+    assert setup_helpers["_is_unresolved_math_library_directory"](entry) is False
+    # Also through the production predicate, not just the narrow one. Asserting only the narrow
+    # predicate let _is_usable_runtime_path start rejecting an ordinary system directory with the
+    # whole suite green, since nothing checked that these entries actually survive the filter.
+    assert setup_helpers["_is_usable_runtime_path"](entry, True, True) is True
+
+
+# Read off the pybindings extension in the published x86_64 CPU nightly, in the recorded order. The
+# MKL block sits after five relative hops and before one. On this wheel the entries are simply dead,
+# since nothing resolves through them, so dropping them costs a few wasted lookups at load time and
+# removes paths a user cannot have. On the CUDA wheel the same block precedes the hop into the CUDA
+# runtime, which is where the ordering matters.
+SHIPPED_RUNTIME_PATH = [
+    "$ORIGIN/../../../torch/lib",
+    "$ORIGIN/../../src/executorch/lib",
+    "$ORIGIN/../../backends/qualcomm",
+    "$ORIGIN/../../lib",
+    "$ORIGIN/../../../lib64",
+    "/lib/intel64",
+    "/lib/intel64_win",
+    "/lib/win-x64",
+    "$ORIGIN/../../backends/cuda",
+]
+
+
+def _relative_torch_route_predicate():
+    """setup.py's own has_relative_torch_route expression, lifted out of its function.
+
+    Read rather than restated, because it decides the third argument to the filter under test.
+    A copy here would let the test keep passing after that expression changed, which is the one
+    failure a regression guard must not have.
+    """
+    tree = ast.parse(_setup_source())
+    for node in ast.walk(tree):
+        if not (
+            isinstance(node, ast.Assign)
+            and any(
+                isinstance(target, ast.Name) and target.id == "has_relative_torch_route"
+                for target in node.targets
+            )
+        ):
+            continue
+        # The expression iterates a name bound in setup.py's own scope, so it is rebound to this
+        # function's argument by compiling it as the body of a one-argument lambda.
+        source = ast.unparse(node.value)
+        iterated = "for entry in found"
+        assert iterated in source, (
+            f"setup.py computes has_relative_torch_route as {source!r}, which no longer iterates "
+            "the name this test rebinds. Update the rebinding rather than leaving it a no-op."
+        )
+        return eval(
+            f"lambda entries: {source.replace(iterated, 'for entry in entries')}"
+        )
+    raise AssertionError(
+        "setup.py no longer computes has_relative_torch_route, so this test would pass the "
+        "filter an argument the shipped code never produces."
+    )
+
+
+def _filtered(entries, setup_helpers):
+    is_usable = setup_helpers["_is_usable_runtime_path"]
+    has_relative_torch_route = _relative_torch_route_predicate()(entries)
+    return [
+        entry
+        for entry in entries
+        # True is safe_to_drop_toolkit_paths: this wheel ships no CUDA, so an absolute toolkit path
+        # in it names only the build machine. Packaging derives the same value from the built tree.
+        if is_usable(entry, True, has_relative_torch_route)
+    ]
+
+
+def test_shipped_library_keeps_no_absolute_entry(setup_helpers):
+    kept = _filtered(SHIPPED_RUNTIME_PATH, setup_helpers)
+    assert [entry for entry in kept if entry.startswith("/")] == []
+
+
+def test_shipped_library_keeps_every_relative_hop(setup_helpers):
+    # Asserted separately from the absence of absolute entries, because a filter that dropped
+    # everything would satisfy that one while leaving the library unable to find its siblings.
+    kept = _filtered(SHIPPED_RUNTIME_PATH, setup_helpers)
+    assert kept == [
+        entry for entry in SHIPPED_RUNTIME_PATH if not entry.startswith("/")
+    ]
+
+
+def test_keeps_the_absolute_torch_directory_when_it_is_the_only_route(setup_helpers):
+    # The case that stops this being a blanket "drop everything absolute": an extension links
+    # torch and, with no relative route recorded, reaches it only through the directory the
+    # linker found it in. Dropping that would stop the extension importing.
+    entries = [
+        "/opt/conda/envs/py_3.12/lib/python3.12/site-packages/torch/lib",
+        "/lib/intel64",
+    ]
+    assert _filtered(entries, setup_helpers) == [entries[0]]
+
+
+def test_drops_the_absolute_torch_directory_when_a_relative_route_exists(setup_helpers):
+    # The other side of the same rule, and the only case that exercises the route expression at all.
+    # Without a relative entry in the list the route is False whatever that expression says, so the
+    # test above cannot tell a correct expression from an inverted one.
+    entries = [
+        "$ORIGIN/../../../torch/lib",
+        "/opt/conda/envs/py_3.12/lib/python3.12/site-packages/torch/lib",
+        "/lib/intel64",
+    ]
+    assert _filtered(entries, setup_helpers) == [entries[0]]
+
+
+_MATH_DIRECTORY_REASON = "a maths library directory whose prefix resolved empty"
+_BUILD_DIRECTORY_REASON = "inside a build of this project"
+_UNREACHABLE_REASON = "an absolute directory the wheel has a relative route to"
+
+
+def _release_check_decision():
+    """The release check's own per-entry decision, imported rather than replayed.
+
+    Loaded as a module so the unit test exercises the function the wheel check calls, rather than
+    that function's source text. Reading the text let the rejection be deleted outright.
+    """
+    path = REPO_ROOT / ".ci" / "scripts" / "wheel" / "test_shared_libraries.py"
+    spec = importlib.util.spec_from_file_location("_release_check_under_test", path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module._unusable_runtime_path_kind
+
+
+@pytest.mark.parametrize("arch", _MKL_ARCH_DIRECTORIES)
+def test_release_check_rejects_the_math_directories(arch):
+    # The check and packaging are separate code, so a wheel built without patchelf keeps these
+    # entries and only the check would catch it. Driven off setup.py's own constant, and asserting
+    # the REASON rather than merely a rejection: the check rejects every absolute path it does not
+    # recognise, so an arch it was never taught about would otherwise pass through the catch-all.
+    decide = _release_check_decision()
+    assert (
+        decide(f"/lib/{arch}", "_C.cpython-312-x86_64-linux-gnu.so")
+        == _MATH_DIRECTORY_REASON
+    )
+
+
+def test_release_check_rejects_each_kind_for_its_own_reason():
+    # One assertion per rejecting branch, by reason, so deleting any single branch fails here.
+    # Asserting only "not None" let the build-directory branch and the catch-all each be removed
+    # on their own with every test green.
+    decide = _release_check_decision()
+    assert decide("/home/u/pip-out/lib", "_C.so") == _BUILD_DIRECTORY_REASON
+    assert decide("/opt/rocm/lib", "_C.so") == _UNREACHABLE_REASON
+    assert decide("", "_C.so") is not None
+
+
+def test_release_check_rejects_a_build_directory_before_the_allowlist():
+    # Order is load bearing and nothing else holds it. A torch directory inside a CI worker tree
+    # must be rejected, which only happens because the build-directory branch runs before the
+    # suffix allowlist gets to accept the /torch/lib ending.
+    decide = _release_check_decision()
+    entry = "/home/ec2-user/actions-runner/_work/executorch/pytorch/torch/lib"
+    assert decide(entry, "_C.so") == _BUILD_DIRECTORY_REASON
+
+
+@pytest.mark.parametrize("arch", _MKL_ARCH_DIRECTORIES)
+def test_release_check_still_accepts_a_real_mkl_installation(arch, setup_helpers):
+    # The two must agree on every arch in the shared constant. Packaging KEEPS a prefixed one,
+    # because the environment provides it, so a check that rejected it would fail a wheel packaging
+    # deliberately allowed and the builder could not satisfy both. Parametrized off the constant, so
+    # adding an arch to setup.py without teaching the check about it fails here.
+    entry = f"/opt/intel/mkl/lib/{arch}"
+    assert setup_helpers["_is_usable_runtime_path"](entry, True, True) is True
+    assert (
+        _release_check_decision()(entry, "_C.cpython-312-x86_64-linux-gnu.so") is None
+    )
+
+
+def test_the_wheel_scan_consults_the_classifier():
+    # The unit tests above call the classifier directly, and the wheel scan is the only thing that
+    # applies it to a real library. That scan needs an installed wheel, so it cannot run here;
+    # what is checkable is the wiring, and severing it left all tests green. Asserted on the AST so
+    # a rename or an accidental deletion fails rather than silently disabling the enforcement.
+    path = REPO_ROOT / ".ci" / "scripts" / "wheel" / "test_shared_libraries.py"
+    tree = ast.parse(path.read_text(encoding="utf-8"))
+    scan = next(
+        (
+            node
+            for node in ast.walk(tree)
+            if isinstance(node, ast.FunctionDef)
+            and node.name == "test_no_absolute_runtime_paths"
+        ),
+        None,
+    )
+    assert scan is not None, "the wheel scan this check enforces no longer exists"
+    called = {
+        node.func.id
+        for node in ast.walk(scan)
+        if isinstance(node, ast.Call) and isinstance(node.func, ast.Name)
+    }
+    assert "_unusable_runtime_path_kind" in called, (
+        "test_no_absolute_runtime_paths no longer calls _unusable_runtime_path_kind, so the wheel "
+        "scan would report every shipped library clean while these unit tests still pass."
+    )
+
+
+def test_release_check_accepts_a_relative_entry():
+    # A relative hop is the normal case and must never be rejected, whatever the absolute rules do.
+    assert _release_check_decision()("$ORIGIN/../../lib", "_C.so") is None