Support 'list_concat_unique'

Adds function 'list_concat_unique' to concat
several lists using python's extend function
and make sure without repeating items.

Blueprint: support-list-concat-unique-function
Change-Id: Ia0e35eb578ebe91543c644155a86030b3258118b

doc/source/template_guide/hot_spec.rst

@@ -295,8 +295,10 @@ for the ``heat_template_version`` key:
     document is a HOT template and it may contain features added and/or removed
     up until the Pike release. This version adds the ``make_url`` function for
     assembling URLs, the ``list_concat`` function for combining multiple
-    lists, and ``string_replace_vstrict`` which raises errors for
-    missing and empty params. The complete list of supported functions is::
+    lists, the ``list_concat_unique`` function for combining multiple
+    lists without repeating items, and the``string_replace_vstrict`` which
+    raises errors for missing and empty params. The complete list of
+    supported functions is::
 
       digest
       filter
@@ -307,6 +309,7 @@ for the ``heat_template_version`` key:
       list_join
       make_url
       list_concat
+      list_concat_unique
       map_merge
       map_replace
       repeat
@@ -1931,3 +1934,17 @@ For example
 Will resolve to the list ``['v1', 'v2', 'v3', 'v4']``.
 
 Null values will be ignored.
+
+list_concat_unique
+------------------
+
+The ``list_concat_unique`` function behaves identically to the function
+``list_concat``, only removes the repeating items of lists.
+
+For example
+
+.. code-block:: yaml
+
+    list_concat_unique: [['v1', 'v2'], ['v2', 'v43']]
+
+Will resolve to the list ``['v1', 'v2', 'v3']``.

heat/engine/hot/functions.py

@@ -1480,6 +1480,8 @@ class ListConcat(function.Function):
 
     """
 
+    _unique = False
+
     def __init__(self, stack, fn_name, args):
         super(ListConcat, self).__init__(stack, fn_name, args)
         example = (_('"%s" : [ [ <value 1>, <value 2> ], '
@@ -1508,4 +1510,20 @@ class ListConcat(function.Function):
         ret_list = []
         for m in args:
             ret_list.extend(ensure_list(m))
+
+        if self._unique:
+            for i in ret_list:
+                while ret_list.count(i) > 1:
+                    del ret_list[ret_list.index(i)]
+
         return ret_list
+
+
+class ListConcatUnique(ListConcat):
+    """A function for extending lists with unique items.
+
+    list_concat_unique is identical to the list_concat function, only
+    contains unique items in retuning list.
+    """
+
+    _unique = True

heat/engine/hot/template.py

@@ -592,6 +592,7 @@ class HOTemplate20170901(HOTemplate20170224):
         'make_url': hot_funcs.MakeURL,
         'list_concat': hot_funcs.ListConcat,
         'str_replace_vstrict': hot_funcs.ReplaceJsonVeryStrict,
+        'list_concat_unique': hot_funcs.ListConcatUnique,
 
         # functions removed from 2015-10-15
         'Fn::Select': hot_funcs.Removed,

heat/tests/test_hot.py

@@ -2125,6 +2125,34 @@ conditions:
         resolved = self.resolve(snippet, tmpl)
         self.assertEqual(snippet_resolved, resolved)
 
+    def test_list_concat_repeat_dict_item(self):
+        snippet = {'list_concat': [[{'v1': 'v2'}], [{'v1': 'v2'}]]}
+        snippet_resolved = [{'v1': 'v2'}, {'v1': 'v2'}]
+        tmpl = template.Template(hot_pike_tpl_empty)
+        resolved = self.resolve(snippet, tmpl)
+        self.assertEqual(snippet_resolved, resolved)
+
+    def test_list_concat_repeat_item(self):
+        snippet = {'list_concat': [['v1', 'v2'], ['v2', 'v3']]}
+        snippet_resolved = ['v1', 'v2', 'v2', 'v3']
+        tmpl = template.Template(hot_pike_tpl_empty)
+        resolved = self.resolve(snippet, tmpl)
+        self.assertEqual(snippet_resolved, resolved)
+
+    def test_list_concat_unique_dict_item(self):
+        snippet = {'list_concat_unique': [[{'v1': 'v2'}], [{'v1': 'v2'}]]}
+        snippet_resolved = [{'v1': 'v2'}]
+        tmpl = template.Template(hot_pike_tpl_empty)
+        resolved = self.resolve(snippet, tmpl)
+        self.assertEqual(snippet_resolved, resolved)
+
+    def test_list_concat_unique(self):
+        snippet = {'list_concat_unique': [['v1', 'v2'], ['v2', 'v3']]}
+        snippet_resolved = ['v1', 'v2', 'v3']
+        tmpl = template.Template(hot_pike_tpl_empty)
+        resolved = self.resolve(snippet, tmpl)
+        self.assertEqual(snippet_resolved, resolved)
+
     def _test_list_concat_invalid(self, snippet):
         tmpl = template.Template(hot_pike_tpl_empty)
         msg = 'Incorrect arguments'

releasenotes/notes/add-list-concat-unique-function-5a87130d9c93cb08.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - The list_concat_unique function was added, which behaves identically
+    to the function ``list_concat`` to concat several lists using
+    python's extend function and make sure without repeating items.