Fix Python 3.x try/else detection

Fixes #155

test/simple_source/bug31/01_try_else.py

@@ -0,0 +1,23 @@
+# Bug based on 2.7 test_itertools.py but mis-decompiled in Python 3.x bytecode
+# The bug is confusing "try/else" with "try" as a result of the loop which causes
+# the end of the except to jump back to the beginning of the loop, outside of the
+# try. In 3.x we not distinguising this jump out of the loop with a jump to the
+# end of the "try".
+
+def testit(stmts):
+
+    # Bug was confusing When the except jumps back to the beginning of the block
+    # to the beginning of this for loop
+    x = 1
+    results = []
+    for stmt in stmts:
+        try:
+            x = eval(stmt)
+        except SyntaxError:
+            results.append(1)
+        else:
+            results.append(x)
+    return results
+
+results = testit(["1 + 2", "1 +"])
+assert results == [3, 1], "try with else failed"

uncompyle6/parsers/parse3.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2015-2018 Rocky Bernstein
+#  Copyright (c) 2015-2019 Rocky Bernstein
 #  Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
 #  Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
 #  Copyright (c) 1999 John Aycock
@@ -185,23 +185,11 @@ class Python3Parser(PythonParser):
         # one COME_FROM for Python 2.7 seems to associate the
         # COME_FROM targets from the wrong places
 
-        try_except     ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
-                           except_handler opt_come_from_except
-
         # this is nested inside a try_except
         tryfinallystmt ::= SETUP_FINALLY suite_stmts_opt
                            POP_BLOCK LOAD_CONST
                            COME_FROM_FINALLY suite_stmts_opt END_FINALLY
 
-        tryelsestmt    ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
-                           except_handler else_suite come_from_except_clauses
-
-        tryelsestmt    ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
-                           except_handler else_suite come_froms
-
-        tryelsestmtl   ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
-                           except_handler else_suitel come_from_except_clauses
-
         except_handler ::= jmp_abs COME_FROM except_stmts
                            END_FINALLY
         except_handler ::= jmp_abs COME_FROM_EXCEPT except_stmts
@@ -564,9 +552,10 @@ class Python3Parser(PythonParser):
         # include instructions that don't need customization,
         # but we'll do a finer check after the rough breakout.
         customize_instruction_basenames = frozenset(
-            ('BUILD', 'CALL', 'CONTINUE', 'DELETE', 'GET',
+            ('BUILD', 'CALL',   'CONTINUE',    'DELETE', 'GET',
-             'JUMP',  'LOAD', 'LOOKUP',   'MAKE',
+             'JUMP',  'LOAD',   'LOOKUP',      'MAKE',
-             'RETURN', 'RAISE', 'UNPACK'))
+             'RETURN', 'RAISE', 'SETUP',
+             'UNPACK'))
 
         # Opcode names in the custom_ops_processed set have rules that get added
         # unconditionally and the rules are constant. So they need to be done
@@ -1119,6 +1108,26 @@ class Python3Parser(PythonParser):
                     raise_stmt2 ::= expr expr RAISE_VARARGS_2
                     """, nop_func)
                 custom_ops_processed.add(opname)
+            elif opname == 'SETUP_EXCEPT':
+                self.addRule("""
+                    try_except     ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+                                       except_handler opt_come_from_except
+
+                    tryelsestmt    ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+                                       except_handler else_suite come_from_except_clauses
+
+                    tryelsestmt    ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+                                       except_handler else_suite come_froms
+
+                    tryelsestmtl   ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+                                       except_handler else_suitel come_from_except_clauses
+
+                    stmt             ::= tryelsestmtl3
+                    tryelsestmtl3    ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+                                         except_handler COME_FROM else_suitel
+                                         opt_come_from_except
+                    """, nop_func)
+                custom_ops_processed.add(opname)
             elif opname_base in ('UNPACK_EX',):
                 before_count, after_count = token.attr
                 rule = 'unpack ::= ' + opname + ' store' * (before_count + after_count + 1)
@@ -1140,6 +1149,8 @@ class Python3Parser(PythonParser):
         self.check_reduce['ifelsestmt'] = 'AST'
         self.check_reduce['annotate_tuple'] = 'noAST'
         self.check_reduce['kwarg'] = 'noAST'
+        self.check_reduce['try_except'] = 'AST'
+
         # FIXME: remove parser errors caused by the below
         # self.check_reduce['while1elsestmt'] = 'noAST'
         return
@@ -1181,6 +1192,16 @@ class Python3Parser(PythonParser):
             if last == n:
                 return False
             return tokens[first].attr > tokens[last].offset
+        elif rule == ('try_except',
+                      ('SETUP_EXCEPT', 'suite_stmts_opt', 'POP_BLOCK',
+                       'except_handler', 'opt_come_from_except')):
+            come_from_except = ast[-1]
+            if come_from_except[0] == 'COME_FROM':
+                # There should be at last two COME_FROMs, one from an
+                # exception handler and one from the try. Otherwise
+                # we have a try/else.
+                return True
+            pass
         elif lhs == 'while1stmt':
 
             # If there is a fall through to the COME_FROM_LOOP. then this is

uncompyle6/parsers/parse36.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2016-2018 Rocky Bernstein
+#  Copyright (c) 2016-2019 Rocky Bernstein
 #
 #  This program is free software: you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -122,6 +122,7 @@ class Python36Parser(Python35Parser):
         # """)
         super(Python36Parser, self).customize_grammar_rules(tokens, customize)
         self.remove_rules("""
+           except_handler     ::= JUMP_FORWARD COME_FROM_EXCEPT except_stmts END_FINALLY COME_FROM
            async_for_stmt     ::= SETUP_LOOP expr
                                   GET_AITER
                                   LOAD_CONST YIELD_FROM SETUP_EXCEPT GET_ANEXT LOAD_CONST
@@ -344,7 +345,7 @@ class Python36Parser(Python35Parser):
                 if nt[0] == 'call_kw':
                     return True
                 nt = nt[0]
-
+                pass
         return False
 class Python36ParserSingle(Python36Parser, PythonParserSingle):
     pass

uncompyle6/scanners/scanner2.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2015-2018 by Rocky Bernstein
+#  Copyright (c) 2015-2019 by Rocky Bernstein
 #  Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
 #  Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
 #
@@ -886,9 +886,10 @@ class Scanner2(Scanner):
             # or a conditional assignment like:
             #   x = 1 if x else 2
             #
-            # There are other contexts we may need to consider
+            # There are other situations we may need to consider, like
-            # like whether the target is "END_FINALLY"
+            # if the condition jump is to a forward location.
-            # or if the condition jump is to a forward location
+            # Also the existence of a jump to the instruction after "END_FINALLY"
+            # will distinguish "try/else" from "try".
             code_pre_rtarget = code[pre_rtarget]
 
             if code_pre_rtarget in self.jump_forward:

uncompyle6/scanners/scanner3.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2015-2018 by Rocky Bernstein
+#  Copyright (c) 2015-2019 by Rocky Bernstein
 #  Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
 #  Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
 #
@@ -851,7 +851,7 @@ class Scanner3(Scanner):
             # For 3.5, in addition the JUMP_FORWARD above we could have
             # JUMP_BACK or CONTINUE
             #
-            # There are other situations we may need to consider
+            # There are other situations we may need to consider, like
             # if the condition jump is to a forward location.
             # Also the existence of a jump to the instruction after "END_FINALLY"
             # will distinguish "try/else" from "try".

uncompyle6/semantics/customize3.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2018 by Rocky Bernstein
+#  Copyright (c) 2018-2019 by Rocky Bernstein
 #
 #  This program is free software: you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -263,6 +263,12 @@ def customize_for_version3(self, version):
         self.prune() # stop recursing
     self.n_mkfunc_annotate = n_mkfunc_annotate
 
+    TABLE_DIRECT.update({
+                'tryelsestmtl3': ( '%|try:\n%+%c%-%c%|else:\n%+%c%-',
+                                   (1, 'suite_stmts_opt'),
+                                   (3, 'except_handler'),
+                                   (5, 'else_suitel') ),
+        })
     if version >= 3.4:
         ########################
         # Python 3.4+ Additions