Fix 3.5+ bug in if's with pass bodies

Fixes #104 in a somewhat hacky way.

pytest/test_fjt.py

@@ -66,6 +66,9 @@ def test_if_in_for():
         scan.build_lines_data(code)
         scan.build_prev_op()
         scan.insts = list(bytecode)
+        scan.offset2inst_index = {}
+        for i, inst in enumerate(scan.insts):
+            scan.offset2inst_index[inst.offset] = i
         fjt  = scan.find_jump_targets(False)
         assert {69: [66], 63: [18]} == fjt
         assert scan.structs == \

test/simple_source/bug35/05_empty_ifs.py

@@ -0,0 +1,9 @@
+# Issue 104 seen in Python 3.5
+# Since we have empty statement bodies the if's can get confused
+# with "and/or". There is a lot of flakiness in control flow here,
+# and this needs to be straightened out in a more uniform way
+if __file__:
+    if __name__:
+        pass
+    elif __import__:
+        pass

uncompyle6/scanners/scanner3.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2015-2017 by Rocky Bernstein
+#  Copyright (c) 2015-2018 by Rocky Bernstein
 #  Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
 #  Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
 """
@@ -767,18 +767,25 @@ class Scanner3(Scanner):
             # not myself?  If so, it's part of a larger conditional.
             # rocky: if we have a conditional jump to the next instruction, then
             # possibly I am "skipping over" a "pass" or null statement.
+            pretarget = self.insts[self.offset2inst_index[prev_op[target]]]
 
-            if ((code[prev_op[target]] in self.pop_jump_if_pop) and
-                (target > offset) and prev_op[target] != offset):
-                # FIXME: this is not accurate The commented out below
-                # is what it should be. However grammar rules right now
-                # assume the incorrect offsets.
-                # self.fixed_jumps[offset] = target
-                self.fixed_jumps[offset] = prev_op[target]
-                self.structs.append({'type': 'and/or',
-                                     'start': start,
-                                     'end': prev_op[target]})
-                return
+            if (pretarget.opcode in self.pop_jump_if_pop and
+                (target > offset) and pretarget.offset != offset):
+
+                # FIXME: hack upon hack...
+                # In some cases the pretarget can be a jump to the next instruction
+                # and these aren't and/or's either. We limit to 3.5+ since we experienced there
+                # but it might be earlier versions, or might be a general principle.
+                if self.version < 3.5 or pretarget.argval != target:
+                    # FIXME: this is not accurate The commented out below
+                    # is what it should be. However grammar rules right now
+                    # assume the incorrect offsets.
+                    # self.fixed_jumps[offset] = target
+                    self.fixed_jumps[offset] = pretarget.offset
+                    self.structs.append({'type': 'and/or',
+                                         'start': start,
+                                         'end': pretarget.offset})
+                    return
 
             # The opcode *two* instructions before the target jump offset is important
             # in making a determination of what we have. Save that.

uncompyle6/scanners/scanner36.py

@@ -1,4 +1,4 @@
-#  Copyright (c) 2016-2017 by Rocky Bernstein
+#  Copyright (c) 2016-2018 by Rocky Bernstein
 """
 Python 3.6 bytecode decompiler scanner
 
@@ -13,8 +13,6 @@ from __future__ import print_function
 
 from uncompyle6.scanners.scanner3 import Scanner3
 
-import xdis
-
 # bytecode verification, verify(), uses JUMP_OPS from here
 from xdis.opcodes import opcode_36 as opc
 JUMP_OPS = opc.JUMP_OPS