Torture harness: check for leaked file descriptors on macOS too

check_resources() listed /proc/self/fd, which only exists on Linux, so on
macOS every scenario crashed at the end with FileNotFoundError. macOS now
lists /dev/fd and resolves each descriptor with fcntl F_GETPATH, which,
like /proc, still reports files that have been deleted (psutil's
open_files() leaves those out). The temp directory is compared via
realpath(), since macOS reports /var/folders as /private/var/folders.

The test now fails with the harness's stderr when it exits without a
summary line, instead of an IndexError that hid the real traceback.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/connection_torture.py

@@ -295,6 +295,29 @@ class Hang(Exception):
     pass
 
 
+def open_file_paths():
+    # Paths of every file this process has open, including files that have
+    # since been deleted (psutil's open_files() leaves those out)
+    paths = []
+    if os.path.isdir("/proc/self/fd"):
+        for fd in os.listdir("/proc/self/fd"):
+            try:
+                paths.append(os.readlink(f"/proc/self/fd/{fd}"))
+            except OSError:
+                continue
+        return paths
+    # macOS: no /proc, but F_GETPATH works on any open descriptor
+    import fcntl
+
+    for fd in os.listdir("/dev/fd"):
+        try:
+            path = fcntl.fcntl(int(fd), fcntl.F_GETPATH, bytes(1024))
+        except OSError:
+            continue
+        paths.append(os.fsdecode(path.rstrip(b"\0")))
+    return paths
+
+
 def make_file(path, wal=False, extra_sql=""):
     conn = sqlite3.connect(path)
     if wal:
@@ -1190,16 +1213,15 @@ class Torture:
 
     def check_resources(self, baseline_threads):
         deadline = time.monotonic() + 15
+        # On macOS the temp directory is reported via its /private symlink target
+        tmp = os.path.realpath(self.tmp)
         while True:
             gc.collect()
-            leaked_fds = []
-            for fd in os.listdir("/proc/self/fd"):
-                try:
-                    target = os.readlink(f"/proc/self/fd/{fd}")
-                except OSError:
-                    continue
-                if target.startswith(self.tmp) or "datasette_temp_" in target:
-                    leaked_fds.append(target)
+            leaked_fds = [
+                target
+                for target in open_file_paths()
+                if target.startswith(tmp) or "datasette_temp_" in target
+            ]
             threads = [
                 t.name
                 for t in threading.enumerate()

tests/test_connection_torture.py

@@ -58,7 +58,13 @@ def test_connection_torture(scenario, seed):
             f"{scenario} crashed with {signal.Signals(-proc.returncode).name}:\n"
             f"{proc.stderr[-4000:]}"
         )
-    summary = json.loads(proc.stdout.strip().splitlines()[-1])
+    lines = proc.stdout.strip().splitlines()
+    if not lines:
+        pytest.fail(
+            f"{scenario} exited {proc.returncode} without a summary:\n"
+            f"{proc.stderr[-4000:]}"
+        )
+    summary = json.loads(lines[-1])
     problems = "\n".join(
         f"[{p['kind']}] {p['message'][:600]}" for p in summary["problems"]
     )