Fix processing of bits type (#364)

* Add a default of -1 to max(allowed_bits), to cover cases where allowed_bits is empty (e.g. in the absence of any position statements). This will yield an initial implicit position of 0.
* allowed_bits is a dict. Take the maximum of its values.
* Raise ValueError, if pos exceeds its bounds.
* Add test case.

Author: dthiele

pyangbind/plugin/pybind.py

@@ -1359,7 +1359,9 @@ def build_elemtype(ctx, et, prefix=False):
                 if position is not None:
                     pos = position.arg
                 else:
-                    pos = 1 + max(allowed_bits)
+                    pos = 1 + max(allowed_bits.values(), default=-1)
+                    if pos < 0 or 4294967295 < pos:
+                        raise ValueError("position out of bounds")
                 allowed_bits[bit.arg] = pos
             cls = "restricted-bits"
             elemtype = {

tests/bits/bits.yang

@@ -46,4 +46,11 @@ module bits {
     }
     default "flag1 flag3";
   }
+
+  // a leaf containing the bits type definition without position statement
+  leaf bits3 {
+    type bits {
+      bit position0;
+    }
+  }
 }

tests/bits/run.py

@@ -56,6 +56,9 @@ def test_bits_position(self):
         self.instance.bits2.add("foo")
         self.assertEqual(str(self.instance.bits2), "foo bar baz")
 
+    def test_bits_no_position(self):
+        self.assertEqual(self.instance.bits3._allowed_bits["position0"], 0)
+
 
 if __name__ == "__main__":
     unittest.main()