[Plugin] fix predicate precedence in get_predicate()

The get_predicate() method is responsible for evaluating the
precedence of the three types of predicate:

 * Explicit predicate passed as `pred` keyword argument
 * Implicit command default predicate if processing a command
 * Implicit plugin default predicate

Fix the ordering of checks in get_predicate() so that these rules
are consistently followed.

Related: #1616

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/sos/plugins/__init__.py b/sos/plugins/__init__.py
index 0d245013..a2c9ba6c 100644
--- a/sos/plugins/__init__.py
+++ b/sos/plugins/__init__.py
@@ -379,9 +379,11 @@ class Plugin(object):
             If no default predicate is set and a `pred` value is passed
             it will be returned.
         """
-        if cmd and self.cmd_predicate:
+        if pred is not None:
+            return pred
+        if cmd and self.cmd_predicate is not None:
             return self.cmd_predicate
-        return pred or self.predicate
+        return self.predicate
 
     def test_predicate(self, cmd=False, pred=None):
         """Test the current predicate and return its value.