tests: add infrastructure for test resources

We currently only have one test resource file, sample.coredump.zst, but
the tests for #332 will add more. Create a package, tests.resources, to
contain test resources and a function, get_resource(), to decompress
them. It can also be used on the command line:

  python3 -m tests.resources $resource_name

Signed-off-by: Omar Sandoval <osandov@osandov.com>

MANIFEST.in

@@ -1,5 +1,6 @@
 recursive-include docs *.css *.ico *.png *.py *.rst
-recursive-include tests *.py *.zst
+recursive-include tests *.py
+recursive-include tests/resources *.zst
 include tests/linux_kernel/kmod/Makefile tests/linux_kernel/kmod/drgn_test.c
 recursive-include contrib *.py *.rst
 recursive-include tools *.py *.rst

tests/resources/.gitignore

@@ -0,0 +1,5 @@
+*
+!/.gitignore
+!/__init__.py
+!/__main__.py
+!*.zst

tests/resources/__init__.py

@@ -0,0 +1,39 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+import os
+from pathlib import Path
+import subprocess
+import tempfile
+import unittest
+
+from util import out_of_date
+
+
+def get_resource(name: str) -> Path:
+    dir = Path(__file__).parent
+    decompressed_path = dir / name
+    compressed_path = dir / (name + ".zst")
+    if out_of_date(decompressed_path, compressed_path):
+        tmp_file = tempfile.NamedTemporaryFile(dir=dir, prefix=name, delete=False)
+        try:
+            try:
+                subprocess.check_call(
+                    [
+                        "zstd",
+                        "--quiet",
+                        "--force",
+                        "--decompress",
+                        "--stdout",
+                        str(compressed_path),
+                    ],
+                    stdout=tmp_file,
+                )
+            except FileNotFoundError:
+                raise unittest.SkipTest("zstd not found")
+        except BaseException:
+            os.unlink(tmp_file.name)
+            raise
+        else:
+            os.rename(tmp_file.name, decompressed_path)
+    return decompressed_path

tests/resources/__main__.py

@@ -0,0 +1,15 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+import argparse
+
+from tests.resources import get_resource
+
+parser = argparse.ArgumentParser(
+    description="decompress test resources and print their paths"
+)
+parser.add_argument("name", nargs="+", help="resource name")
+args = parser.parse_args()
+
+for name in args.name:
+    print(get_resource(name))

tests/test_thread.py

@@ -3,12 +3,10 @@
 
 import os
 import os.path
-import subprocess
-import tempfile
-import unittest
 
 from drgn import Program
 from tests import TestCase
+from tests.resources import get_resource
 
 
 class TestLive(TestCase):
@@ -60,23 +58,8 @@ class TestCoreDump(TestCase):
     @classmethod
     def setUpClass(cls):
         super().setUpClass()
-        with tempfile.NamedTemporaryFile() as core_dump_file:
-            try:
-                subprocess.check_call(
-                    [
-                        "zstd",
-                        "--quiet",
-                        "--force",
-                        "--decompress",
-                        "--stdout",
-                        os.path.join(os.path.dirname(__file__), "sample.coredump.zst"),
-                    ],
-                    stdout=core_dump_file,
-                )
-            except FileNotFoundError:
-                raise unittest.SkipTest("zstd not found")
-            cls.prog = Program()
-            cls.prog.set_core_dump(core_dump_file.name)
+        cls.prog = Program()
+        cls.prog.set_core_dump(get_resource("multithreaded.core"))
 
     def test_threads(self):
         self.assertSequenceEqual(