Do not delete EXTENDED_ARG instructions that have no arg (#24)

* Fix for missing / mismatched jump labels in ConcreteBytecode.to_bytecode

* Add test that fails without fix and passes with fix

* Fix style in bytecode/tests/test_concrete.py

* increment to v0.5.1

* update version to 0.5.1

bytecode/__init__.py

@@ -1,4 +1,4 @@
-__version__ = '0.5'
+__version__ = '0.5.1'
 
 __all__ = ['Label', 'Instr', 'SetLineno', 'Bytecode',
            'ConcreteInstr', 'ConcreteBytecode',

bytecode/concrete.py

@@ -189,8 +189,10 @@ def from_code(code, *, extended_arg=False):
                         extended_arg = (extended_arg << 8) + instr.arg
                     else:
                         extended_arg = instr.arg
-                    del instructions[index]
-                    continue
+
+                    if extended_arg > 0:
+                        del instructions[index]
+                        continue
 
                 if extended_arg is not None:
                     if _WORDCODE:

bytecode/tests/test_concrete.py

@@ -479,6 +479,54 @@ def test_label2(self):
         self.assertListEqual(concrete.names, ['test', 'x'])
         self.assertListEqual(concrete.varnames, [])
 
+    def test_label3(self):
+        """
+        When you delete ``extended_arg`` that have a value of 0, the following
+        will fail when calling ``Bytecode.to_concrete_bytecode()`` because
+        it cant find a label to correspond to the jump target
+        """
+        code = get_code("""
+            def func(x):
+                if x == 1:
+                    return x +1
+                elif x == 2:
+                    return x + 1
+                elif x == 3:
+                    return x + 1
+                elif x == 4:
+                    return x + 1
+                elif x == 5:
+                    return x + 1
+                elif x == 6:
+                    return x + 1
+                elif x == 7:
+                    return x + 1
+                elif x == 8:
+                    return x + 1
+                elif x == 9:
+                    return x + 1
+                elif x == 10:
+                    return x + 1
+                elif x == 11:
+                    return x + 1
+                elif x == 12:
+                    return x + 1
+                elif x == 13:
+                    return x + 1
+                elif x == 14:
+                    return x + 1
+                elif x == 15:
+                    return x + 1
+                elif x == 16:
+                    return x + 1
+                elif x == 17:
+                    return x + 1
+                return -1
+        """, function=True)
+        code = Bytecode.from_code(code)
+        concrete = code.to_concrete_bytecode()
+        self.assertIsInstance(concrete, ConcreteBytecode)
+
     def test_setlineno(self):
         # x = 7
         # y = 8

setup.py

@@ -25,7 +25,7 @@
 #  - git commit -a -m "post-release"
 #  - git push
 
-VERSION = '0.5'
+VERSION = '0.5.1'
 
 DESCRIPTION = 'Python module to generate and modify bytecode'
 CLASSIFIERS = [