Fix lookup scoping multi-match ordering

When look-up is occurring the possible provider
ordering is used instead of the scope returned provider
ordering. This causes incorrect matches when look-up
argument names that are produced by multiple providers (at
the same scope level) all providing the same requirement
name.

The scope order should be enforced as the de-facto order
and not the order that the storage unit finds (which is
hash based and varies depending on hash ordering).

Closes-Bug: #1425326

Change-Id: I15f1ee5515758bdc470c0f7dd7a2f616923e5628

taskflow/utils/misc.py

@@ -196,6 +196,37 @@ def parse_uri(uri):
     return netutils.urlsplit(uri)
 
 
+def look_for(haystack, needles, extractor=None):
+    """Find items in haystack and returns matches found (in haystack order).
+
+    Given a list of items (the haystack) and a list of items to look for (the
+    needles) this will look for the needles in the haystack and returns
+    the found needles (if any). The ordering of the returned needles is in the
+    order they are located in the haystack.
+
+    Example input and output:
+
+    >>> from taskflow.utils import misc
+    >>> hay = [3, 2, 1]
+    >>> misc.look_for(hay, [1, 2])
+    [2, 1]
+    """
+    if not haystack:
+        return []
+    if extractor is None:
+        extractor = lambda v: v
+    matches = []
+    for i, v in enumerate(needles):
+        try:
+            matches.append((haystack.index(extractor(v)), i))
+        except ValueError:
+            pass
+    if not matches:
+        return []
+    else:
+        return [needles[i] for (_hay_i, i) in sorted(matches)]
+
+
 def clamp(value, minimum, maximum, on_clamped=None):
     """Clamps a value to ensure its >= minimum and <= maximum."""
     if minimum > maximum: