added validation code for checking decompilation of an expression

pytest/validate.py

@@ -0,0 +1,143 @@
+# future
+from __future__ import print_function
+# std
+import os
+import dis
+import difflib
+import subprocess
+import tempfile
+# compatability
+import six
+# uncompyle6 / xdis
+from uncompyle6 import PYTHON_VERSION, deparse_code
+
+
+def _dis_to_text(co):
+    return dis.Bytecode(co).dis()
+
+
+def print_diff(original, uncompyled):
+    """
+    Try and display a pretty html line difference between the original and
+    uncompyled code and bytecode if elinks and BeautifulSoup are installed
+    otherwise just show the diff.
+
+    :param original: Text describing the original code object.
+    :param uncompyled: Text describing the uncompyled code object.
+    """
+    original_lines = original.split('\n')
+    uncompyled_lines = uncompyled.split('\n')
+    args = original_lines, uncompyled_lines, 'original', 'uncompyled'
+    try:
+        from bs4 import BeautifulSoup
+        diff = difflib.HtmlDiff().make_file(*args)
+        diff = BeautifulSoup(diff, "html.parser")
+        diff.select_one('table[summary="Legends"]').extract()
+    except ImportError:
+        print('\nTo display diff highlighting run:\n    pip install BeautifulSoup4')
+        diff = difflib.HtmlDiff().make_table(*args)
+
+    with tempfile.NamedTemporaryFile(delete=False) as f:
+        f.write(str(diff).encode('utf-8'))
+
+    try:
+        print()
+        html = subprocess.check_output([
+            'elinks',
+            '-dump',
+            '-no-references',
+            '-dump-color-mode',
+            '1',
+            f.name,
+        ]).decode('utf-8')
+        print(html)
+    except:
+        print('\nFor side by side diff install elinks')
+        diff = difflib.Differ().compare(original_lines, uncompyled_lines)
+        print('\n'.join(diff))
+    finally:
+        os.unlink(f.name)
+
+
+def are_instructions_equal(i1, i2):
+    """
+    Determine if two instructions are approximately equal,
+    ignoring certain fields which we allow to differ, namely:
+
+    * code objects are ignore (should probaby be checked) due to address
+    * line numbers
+
+    :param i1: left instruction to compare
+    :param i2: right instruction to compare
+
+    :return: True if the two instructions are approximately equal, otherwise False.
+    """
+    result = (1==1
+        and i1.opname == i2.opname
+        and i1.opcode == i2.opcode
+        and i1.arg == i2.arg
+        # ignore differences due to code objects
+        # TODO : Better way of ignoring address
+        and (i1.argval == i2.argval or '<code object' in str(i1.argval))
+        # TODO : Should probably recurse to check code objects
+        and (i1.argrepr == i2.argrepr or '<code object' in i1.argrepr)
+        and i1.offset == i2.offset
+        # ignore differences in line numbers
+        #and i1.starts_line
+        and i1.is_jump_target == i2.is_jump_target
+    )
+    return result
+
+
+def are_code_objects_equal(co1, co2):
+    """
+    Determine if two code objects are approximately equal,
+    see are_instructions_equal for more information.
+
+    :param i1: left code object to compare
+    :param i2: right code object to compare
+
+    :return: True if the two code objects are approximately equal, otherwise False.
+    """
+    # TODO : Use xdis for python2 compatability
+    instructions1 = dis.Bytecode(co1)
+    instructions2 = dis.Bytecode(co2)
+    for opcode1, opcode2 in zip(instructions1, instructions2):
+        if not are_instructions_equal(opcode1, opcode2):
+            return False
+    return True
+
+
+def validate_uncompyle(text, mode='exec'):
+    """
+    Validate decompilation of the given source code.
+
+    :param text: Source to validate decompilation of.
+    """
+    original_code = compile(text, '<string>', mode)
+    original_dis = _dis_to_text(original_code)
+    original_text = text
+
+    deparsed = deparse_code(PYTHON_VERSION, original_code,
+                            compile_mode=mode, out=six.StringIO())
+    uncompyled_text = deparsed.text
+    uncompyled_code = compile(uncompyled_text, '<string>', 'exec')
+
+    if not are_code_objects_equal(uncompyled_code, original_code):
+
+        uncompyled_dis = _dis_to_text(uncompyled_text)
+
+        def output(text, dis):
+            width = 60
+            return '\n\n'.join([
+                ' SOURCE CODE '.center(width, '#'),
+                text.strip(),
+                ' BYTECODE '.center(width, '#'),
+                dis
+            ])
+
+        original = output(original_text, original_dis)
+        uncompyled = output(uncompyled_text, uncompyled_dis)
+        print_diff(original, uncompyled)
+
+        assert 'original' == 'uncompyled'