Do not print locals that have no values. Fixes #1275.

CHANGES.rst

@@ -7,7 +7,8 @@
 1.3.7 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Formatting run info no longer includes ``gevent.local.local``
+  objects that have no value in the greenlet. See :issue:`1275`.
 
 
 1.3.6 (2018-08-17)

src/gevent/util.py

@@ -371,6 +371,8 @@ class GreenletTree(object):
         if gr_locals:
             tree.child_data("Greenlet Locals:")
             for (kind, idl), vals in gr_locals:
+                if not vals:
+                    continue # not set in this greenlet; ignore it.
                 tree.child_data("  Local %s at %s" % (kind, hex(idl)))
                 tree.child_multidata("    " + pprint.pformat(vals))
 

src/greentest/test__util.py

@@ -43,6 +43,9 @@ class TestFormat(greentest.TestCase):
         def root():
             l = MyLocal(42)
             assert l
+            # And an empty local.
+            l2 = local.local()
+            assert l2
             gevent.getcurrent().spawn_tree_locals['a value'] = 42
             io = NativeStrIO()
             g = gevent.spawn(util.print_run_info, file=io)
@@ -54,12 +57,15 @@ class TestFormat(greentest.TestCase):
         g.join()
         value = g.value
 
+
         self.assertIn("Spawned at", value)
         self.assertIn("Parent:", value)
         self.assertIn("Spawn Tree Locals", value)
         self.assertIn("Greenlet Locals:", value)
         self.assertIn('MyLocal', value)
         self.assertIn("Printer", value) # The name is printed
+        # Empty locals should not be printed
+        self.assertNotIn('{}', value)
 
 @greentest.skipOnPyPy("See TestFormat")
 class TestTree(greentest.TestCase):