Correctly identify stack level in `_extract_engine`

Add on the needed frame evaluation logic to be able
to correctly locate where users frames start and ours
end so that we can correctly report the stack level in
the deprecation messages (which the warning module will
use to show the location of the users code that is using
the deprecated usage).

Change-Id: Iae5919fb0f79ffbf9e1784723dc8da1cefdb9f27

taskflow/engines/helpers.py

@@ -15,6 +15,8 @@
 #    under the License.
 
 import contextlib
+import itertools
+import traceback
 
 from oslo.utils import importutils
 import six
@@ -34,39 +36,68 @@ ENGINES_NAMESPACE = 'taskflow.engines'
 # The default entrypoint engine type looked for when it is not provided.
 ENGINE_DEFAULT = 'default'
 
+# TODO(harlowja): only used during the deprecation cycle, remove it once
+# ``_extract_engine_compat`` is also gone...
+_FILE_NAMES = [__file__]
+if six.PY2:
+    # Due to a bug in py2.x the __file__ may point to the pyc file & since
+    # we are using the traceback module and that module only shows py files
+    # we have to do a slight adjustment to ensure we match correctly...
+    #
+    # This is addressed in https://www.python.org/dev/peps/pep-3147/#file
+    if __file__.endswith("pyc"):
+        _FILE_NAMES.append(__file__[0:-1])
+_FILE_NAMES = tuple(_FILE_NAMES)
+
 
-@deprecation.renamed_kwarg('engine_conf', 'engine',
-                           version="0.6", removal_version="?",
-                           # This is set to none since this function is called
-                           # from 2 other functions in this module, both of
-                           # which have different stack levels, possibly we
-                           # can fix this in the future...
-                           stacklevel=None)
 def _extract_engine(**kwargs):
     """Extracts the engine kind and any associated options."""
-    options = {}
-    kind = kwargs.pop('engine', None)
-    engine_conf = kwargs.pop('engine_conf', None)
-    if engine_conf is not None:
-        if isinstance(engine_conf, six.string_types):
-            kind = engine_conf
+
+    def _compat_extract(**kwargs):
+        options = {}
+        kind = kwargs.pop('engine', None)
+        engine_conf = kwargs.pop('engine_conf', None)
+        if engine_conf is not None:
+            if isinstance(engine_conf, six.string_types):
+                kind = engine_conf
+            else:
+                options.update(engine_conf)
+                kind = options.pop('engine', None)
+        if not kind:
+            kind = ENGINE_DEFAULT
+        # See if it's a URI and if so, extract any further options...
+        try:
+            uri = misc.parse_uri(kind)
+        except (TypeError, ValueError):
+            pass
         else:
-            options.update(engine_conf)
-            kind = options.pop('engine', None)
-    if not kind:
-        kind = ENGINE_DEFAULT
-    # See if it's a URI and if so, extract any further options...
-    try:
-        uri = misc.parse_uri(kind)
-    except (TypeError, ValueError):
-        pass
+            kind = uri.scheme
+            options = misc.merge_uri(uri, options.copy())
+        # Merge in any leftover **kwargs into the options, this makes it so
+        # that the provided **kwargs override any URI or engine_conf specific
+        # options.
+        options.update(kwargs)
+        return (kind, options)
+
+    engine_conf = kwargs.get('engine_conf', None)
+    if engine_conf is not None:
+        # Figure out where our code ends and the calling code begins (this is
+        # needed since this code is called from two functions in this module,
+        # which means the stack level will vary by one depending on that).
+        finder = itertools.takewhile(lambda frame: frame[0] in _FILE_NAMES,
+                                     reversed(traceback.extract_stack()))
+        stacklevel = sum(1 for _frame in finder)
+        decorator = deprecation.renamed_kwarg('engine_conf', 'engine',
+                                              version="0.6",
+                                              removal_version="?",
+                                              # Three is added on since the
+                                              # decorator adds three of its own
+                                              # stack levels that we need to
+                                              # hop out of...
+                                              stacklevel=stacklevel + 3)
+        return decorator(_compat_extract)(**kwargs)
     else:
-        kind = uri.scheme
-        options = misc.merge_uri(uri, options.copy())
-    # Merge in any leftover **kwargs into the options, this makes it so that
-    # the provided **kwargs override any URI or engine_conf specific options.
-    options.update(kwargs)
-    return (kind, options)
+        return _compat_extract(**kwargs)
 
 
 def _fetch_factory(factory_name):