showemptyattrs option on Node.show() (#570)

* hideemptyattrs option on Node.show()

* slight simplification

* prefer positive logic

Author: cellularmitosis

pycparser/c_ast.py

@@ -55,7 +55,7 @@ def children(self):
         """
         pass
 
-    def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showcoord=False, _my_node_name=None):
+    def show(self, buf=sys.stdout, offset=0, attrnames=False, showemptyattrs=True, nodenames=False, showcoord=False, _my_node_name=None):
         """ Pretty print the Node and all its attributes and
             children (recursively) to a buffer.
 
@@ -69,6 +69,9 @@ def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showc
                 True if you want to see the attribute names in
                 name=value pairs. False to only see the values.
 
+            showemptyattrs:
+                False if you want to suppress printing empty attributes.
+
             nodenames:
                 True if you want to see the actual node names
                 within their parents.
@@ -84,12 +87,13 @@ def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showc
             buf.write(lead + self.__class__.__name__+ ': ')
 
         if self.attr_names:
+            is_empty = lambda v: v is None or (hasattr(v, '__len__') and len(v) == 0)
+            nvlist = [(n, getattr(self,n)) for n in self.attr_names \
+                        if showemptyattrs or not is_empty(getattr(self,n))]
             if attrnames:
-                nvlist = [(n, getattr(self,n)) for n in self.attr_names]
                 attrstr = ', '.join('%s=%s' % nv for nv in nvlist)
             else:
-                vlist = [getattr(self, n) for n in self.attr_names]
-                attrstr = ', '.join('%s' % v for v in vlist)
+                attrstr = ', '.join('%s' % v for (_,v) in nvlist)
             buf.write(attrstr)
 
         if showcoord:
@@ -101,6 +105,7 @@ def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showc
                 buf,
                 offset=offset + 2,
                 attrnames=attrnames,
+                showemptyattrs=showemptyattrs,
                 nodenames=nodenames,
                 showcoord=showcoord,
                 _my_node_name=child_name)