(linux) proc io nice: provide better error messages

2 files changed, 29 insertions, 9 deletions

diff --git a/psutil/_pslinux.py b/psutil/_pslinux.py
index 3f1ff721..f3b5b080 100644
--- a/psutil/_pslinux.py
+++ b/psutil/_pslinux.py
@@ -1044,25 +1044,35 @@ class Process(object):
 
         @wrap_exceptions
         def ionice_set(self, ioclass, value):
+            if value is not None:
+                if not PY3 and not isinstance(value, (int, long)):
+                    msg = "value argument is not an integer (gor %r)" % value
+                    raise TypeError(msg)
+                if not 0 <= value <= 8:
+                    raise ValueError(
+                        "value argument range expected is between 0 and 8")
+
             if ioclass in (IOPRIO_CLASS_NONE, None):
                 if value:
-                    msg = "can't specify value with IOPRIO_CLASS_NONE"
+                    msg = "can't specify value with IOPRIO_CLASS_NONE " \
+                          "(got %r)" % value
                     raise ValueError(msg)
                 ioclass = IOPRIO_CLASS_NONE
                 value = 0
-            if ioclass in (IOPRIO_CLASS_RT, IOPRIO_CLASS_BE):
-                if value is None:
-                    value = 4
             elif ioclass == IOPRIO_CLASS_IDLE:
                 if value:
-                    msg = "can't specify value with IOPRIO_CLASS_IDLE"
+                    msg = "can't specify value with IOPRIO_CLASS_IDLE " \
+                          "(got %r)" % value
                     raise ValueError(msg)
                 value = 0
+            elif ioclass in (IOPRIO_CLASS_RT, IOPRIO_CLASS_BE):
+                if value is None:
+                    # TODO: add comment explaining why this is 4 (?)
+                    value = 4
             else:
-                value = 0
-            if not 0 <= value <= 8:
-                raise ValueError(
-                    "value argument range expected is between 0 and 8")
+                # otherwise we would get OSError(EVINAL)
+                raise ValueError("invalid ioclass argument %r" % ioclass)
+
             return cext.proc_ioprio_set(self.pid, ioclass, value)
 
     if HAS_PRLIMIT:
diff --git a/test/test_psutil.py b/test/test_psutil.py
index 842fff78..bc750fdc 100644
--- a/test/test_psutil.py
+++ b/test/test_psutil.py
@@ -1356,7 +1356,17 @@ class TestProcess(unittest.TestCase):
                 ioclass, value = p.ionice()
                 self.assertEqual(ioclass, 2)
                 self.assertEqual(value, 7)
+                #
                 self.assertRaises(ValueError, p.ionice, 2, 10)
+                self.assertRaises(ValueError, p.ionice, 2, -1)
+                self.assertRaises(ValueError, p.ionice, 4)
+                self.assertRaises(TypeError, p.ionice, 2, "foo")
+                self.assertRaisesRegexp(
+                    ValueError, "can't specify value with IOPRIO_CLASS_NONE",
+                    p.ionice, psutil.IOPRIO_CLASS_NONE, 1)
+                self.assertRaisesRegexp(
+                    ValueError, "can't specify value with IOPRIO_CLASS_IDLE",
+                    p.ionice, psutil.IOPRIO_CLASS_IDLE, 1)
             finally:
                 p.ionice(IOPRIO_CLASS_NONE)
         else: