Fix Python default argument handing broken since swig-3.0.3

Default values are no longer generated as Python code by default.
They must be explicitly turned on using the "python:defaultargs" feature.

Closes #294
Closes #296

The problems in these two issues when "python:defaultargs" is turned
on still need to be fixed and should be addressed in separate patches.
The important thing is the default code generation is now fixed.

CHANGES.current

@@ -5,6 +5,16 @@ See the RELEASENOTES file for a summary of changes in each release.
 Version 3.0.4 (in progress)
 ===========================
 
+2015-01-08: wsfulton
+            [Python] Fix #294 #296 - Regression introduced in SWIG-3.0.3 when
+            wrapping functions with default arguments. Now any method with default
+            arguments obtains the default arguments from C++ instead of generating
+            Python code with the default arguments.
+
+            The "python:defaultargs" feature has been introduced for users to
+            optionally generate Python methods with the default arguments instead
+            the default *args.
+
 2015-01-08: olly
 	    Allow C++11 "explicit constexpr".  Fixes github issue#284 reported
 	    by Paweł Tomulik.  Also handle "constexpr explicit" and "constexpr

Examples/test-suite/default_args.i

@@ -14,7 +14,9 @@
   #include <string>
 
   // All kinds of numbers: hex, octal (which pose special problems to Python), negative...
-  void lots_of_args(int pos = -1, unsigned rgb = 0xabcdef, int mode = 0644) { }
+  void trickyvalue1(int first, int pos = -1) {}
+  void trickyvalue2(int first, unsigned rgb = 0xabcdef) {}
+  void trickyvalue3(int first, int mode = 0644) {}
 
   // Long long arguments are not handled at Python level currently but still work.
   void seek(long long offset = 0LL) {}

Examples/test-suite/python/Makefile.in

@@ -58,6 +58,7 @@ CPP_TEST_CASES += \
 	primitive_types \
 	python_abstractbase \
 	python_append \
+	python_default_args \
 	python_director \
 	python_nondynamic \
 	python_overload_simple_cast \

Examples/test-suite/python/default_args_runme.py

@@ -1,9 +1,16 @@
-import default_args 
+# Note that this test is also used by python_default_args_runme.py hence the use of __main__ and the run function
 
+def run(module_name):
+  default_args = __import__(module_name)
+  print "running...."
   ec = default_args.EnumClass()
   if not ec.blah():
     raise RuntimeError,"EnumClass::blah() default arguments don't work"
 
+  de = default_args.DerivedEnumClass()
+  de.accelerate()
+  de.accelerate(default_args.EnumClass.SLOW)
+
   if default_args.Statics_staticMethod() != 60:
     raise RuntimeError
 
@@ -65,3 +72,20 @@ except:
     error = 0
   if error:  raise RuntimeError,"Foo::meth ignore is not working"
 
+  if default_args.Klass.inc(100, default_args.Klass(22)).val != 122:
+    raise RuntimeError, "Klass::inc failed"
+
+  if default_args.Klass.inc(100).val != 99:
+    raise RuntimeError, "Klass::inc failed"
+
+  if default_args.Klass.inc().val != 0:
+    raise RuntimeError, "Klass::inc failed"
+
+  default_args.trickyvalue1(10); default_args.trickyvalue1(10, 10)
+  default_args.trickyvalue2(10); default_args.trickyvalue2(10, 10)
+  default_args.trickyvalue3(10); default_args.trickyvalue3(10, 10)
+  default_args.seek(); default_args.seek(10)
+
+if __name__=="__main__":
+  run('default_args')
+

Examples/test-suite/python/python_default_args_runme.py

@@ -0,0 +1,3 @@
+# Test %feature("python:defaultargs") using the test code in default_args_runme.py (which does not use the feature)
+import default_args_runme
+default_args_runme.run('python_default_args')

Examples/test-suite/python_default_args.i

@@ -0,0 +1,10 @@
+%module python_default_args
+
+%pythondefaultargs;
+
+// Turn off the feature for the tricky cases that can't be handled
+%nopythondefaultargs seek;
+%nopythondefaultargs Space::Klass::inc;
+%nopythondefaultargs DerivedEnumClass::accelerate;
+
+%include "default_args.i"

Lib/python/pyuserdir.swg

@@ -185,6 +185,16 @@ These methods "may be called" if needed.
 #define %clearpythonappend    %feature("pythonappend","")
 
 
+/* ------------------------------------------------------------------------- */
+/*
+  Python default argument handling (for non-builtin)
+*/
+
+#define %pythondefaultargs      %feature("python:defaultargs")
+#define %nopythondefaultargs    %feature("python:defaultargs", "0")
+#define %clearpythondefaultargs %feature("python:defaultargs", "")
+
+
 
 /* ------------------------------------------------------------------------- */
 /* 

Source/Modules/python.cxx

@@ -1856,6 +1856,10 @@ public:
    *    at C++ code level where they can always be handled.
    * ------------------------------------------------------------ */
   bool is_representable_as_pyargs(Node *n) {
+    bool is_representable = true;
+
+    if (Getattr(n, "sym:overloaded")) {
+      if (GetFlag(n, "feature:python:defaultargs")) {
 	ParmList *plist = CopyParmList(Getattr(n, "parms"));
 	Parm *p;
 	Parm *pnext;
@@ -1872,11 +1876,17 @@ public:
 	  }
 	  if (String *value = Getattr(p, "value")) {
 	    String *type = Getattr(p, "type");
-	if (!convertValue(value, type))
+	    if (!convertValue(value, type)) {
-	  return false;
+	      is_representable = false;
+	      break;
 	    }
 	  }
-    return true;
+	}
+      } else {
+	is_representable = false;
+      }
+    }
+    return is_representable;
   }