fix #2238 if cwd() cannot be determined always return "" instead of None

HISTORY.rst

@@ -15,6 +15,10 @@
     empty string)
   - The function is faster since it no longer iterates over all processes.
   - No longer produces duplicate connection entries.
+- 2238_: there are cases where `Process.cwd()`_ cannot be determined
+  (e.g. directory no longer exists), in which case we returned either ``None``
+  or an empty string. This was consolidated and we now return ``""`` on all
+  platforms.
 
 **Bug fixes**
 
@@ -39,8 +43,8 @@
   *used* are too high. We now match values shown by *htop* CLI utility.
 - 2236_, [NetBSD]: `Process.num_threads()`_ and `Process.threads()`_ return
   threads that are already terminated.
-- 2237_, [OpenBSD]: `Process.cwd()`_ may raise ``FileNotFoundError`` if cwd no
-  longer exists. Return ``None`` instead.
+- 2237_, [OpenBSD], [NetBSD]: `Process.cwd()`_ may raise ``FileNotFoundError``
+  if cwd no longer exists. Return an empty string instead.
 
 5.9.4
 =====

docs/index.rst

@@ -1180,9 +1180,10 @@ Process class
 
   .. method:: exe()
 
-    The process executable as an absolute path.
-    On some systems this may also be an empty string.
-    The return value is cached after first call.
+    The process executable as an absolute path. On some systems, if exe cannot
+    be determined for some internal reason (e.g. system process or path no
+    longer exists), this may be an empty string. The return value is cached
+    after first call.
 
     >>> import psutil
     >>> psutil.Process().exe()
@@ -1281,7 +1282,9 @@ Process class
 
   .. method:: cwd()
 
-    The process current working directory as an absolute path.
+    The process current working directory as an absolute path. If cwd cannot be
+    determined for some internal reason (e.g. system process or directiory no
+    longer exists) it may return an empty string.
 
     .. versionchanged:: 5.6.4 added support for NetBSD
 

psutil/_psaix.py

@@ -487,7 +487,7 @@ def cwd(self):
             return result.rstrip('/')
         except FileNotFoundError:
             os.stat("%s/%s" % (procfs_path, self.pid))  # raise NSP or AD
-            return None
+            return ""
 
     @wrap_exceptions
     def memory_info(self):

psutil/_psbsd.py

@@ -839,7 +839,7 @@ def cwd(self):
         elif NETBSD or HAS_PROC_OPEN_FILES:
             # FreeBSD < 8 does not support functions based on
             # kinfo_getfile() and kinfo_getvmmap()
-            return cext.proc_cwd(self.pid) or None
+            return cext.proc_cwd(self.pid) or ""
         else:
             raise NotImplementedError(
                 "supported only starting from FreeBSD 8" if

psutil/_pssunos.py

@@ -542,7 +542,7 @@ def cwd(self):
             return os.readlink("%s/%s/path/cwd" % (procfs_path, self.pid))
         except FileNotFoundError:
             os.stat("%s/%s" % (procfs_path, self.pid))  # raise NSP or AD
-            return None
+            return ""
 
     @wrap_exceptions
     def memory_info(self):

psutil/arch/netbsd/proc.c

@@ -115,10 +115,13 @@ psutil_proc_cwd(PyObject *self, PyObject *args) {
     ssize_t len = readlink(buf, path, sizeof(path) - 1);
     free(buf);
     if (len == -1) {
-        if (errno == ENOENT)
-            NoSuchProcess("readlink -> ENOENT");
-        else
+        if (errno == ENOENT) {
+            psutil_debug("sysctl(KERN_PROC_CWD) -> ENOENT converted to ''");
+            return Py_BuildValue("", "");
+        }
+        else {
             PyErr_SetFromErrno(PyExc_OSError);
+        }
         return NULL;
     }
     path[len] = '\0';

psutil/arch/openbsd/proc.c

@@ -306,8 +306,8 @@ psutil_proc_cwd(PyObject *self, PyObject *args) {
     int name[] = { CTL_KERN, KERN_PROC_CWD, pid };
     if (sysctl(name, 3, path, &pathlen, NULL, 0) != 0) {
         if (errno == ENOENT) {
-            psutil_debug("sysctl(KERN_PROC_CWD) -> ENOENT converted to None");
-            Py_RETURN_NONE;  // mimic os.cpu_count()
+            psutil_debug("sysctl(KERN_PROC_CWD) -> ENOENT converted to ''");
+            return Py_BuildValue("", "");
         }
         else {
             PyErr_SetFromErrno(PyExc_OSError);

psutil/tests/test_contracts.py

@@ -452,10 +452,9 @@ def cmdline(self, ret, info):
             self.assertIsInstance(part, str)
 
     def exe(self, ret, info):
-        self.assertIsInstance(ret, (str, unicode, type(None)))
-        if not ret:
-            self.assertEqual(ret, '')
-        else:
+        self.assertIsInstance(ret, (str, unicode))
+        self.assertEqual(ret.strip(), ret)
+        if ret:
             if WINDOWS and not ret.endswith('.exe'):
                 return  # May be "Registry", "MemCompression", ...
             assert os.path.isabs(ret), ret
@@ -520,7 +519,8 @@ def gids(self, ret, info):
 
     def username(self, ret, info):
         self.assertIsInstance(ret, str)
-        assert ret
+        self.assertEqual(ret.strip(), ret)
+        assert ret.strip()
 
     def status(self, ret, info):
         self.assertIsInstance(ret, str)
@@ -619,6 +619,7 @@ def open_files(self, ret, info):
         for f in ret:
             self.assertIsInstance(f.fd, int)
             self.assertIsInstance(f.path, str)
+            self.assertEqual(f.path.strip(), f.path)
             if WINDOWS:
                 self.assertEqual(f.fd, -1)
             elif LINUX:
@@ -651,8 +652,9 @@ def connections(self, ret, info):
                 check_connection_ntuple(conn)
 
     def cwd(self, ret, info):
-        if ret:     # 'ret' can be None or empty
-            self.assertIsInstance(ret, str)
+        self.assertIsInstance(ret, (str, unicode))
+        self.assertEqual(ret.strip(), ret)
+        if ret:
             assert os.path.isabs(ret), ret
             try:
                 st = os.stat(ret)

psutil/tests/test_posix.py

@@ -351,12 +351,7 @@ def test_users(self):
                 self.assertEqual(u.name, users[idx])
                 self.assertEqual(u.terminal, terminals[idx])
                 if u.pid is not None:  # None on OpenBSD
-                    p = psutil.Process(u.pid)
-                    # on macOS time is off by ~47 secs for some reason, but
-                    # the next test against 'who' CLI succeeds
-                    delta = 60 if MACOS else 1
-                    self.assertAlmostEqual(
-                        u.started, p.create_time(), delta=delta)
+                    psutil.Process(u.pid)
 
     @retry_on_failure()
     def test_users_started(self):