Allow multiple lists for list_join intrinsic functions

Allow the HOT list_join function to optionally accept multiple
lists.  This is useful when you want to combine two or more lists,
for example to join a hard-coded list with a user provided one.

Although this is 100% backwards compatible, it's been added as a new
function which is available only via the Liberty HOT version.  This
should allow easier determination of whether a particular heat service
supports this revised syntax.

Change-Id: I375450960c6d486998308ec0b915c25628f745a5

heat/engine/hot/functions.py

@@ -236,9 +236,51 @@ class Join(cfn_funcs.Join):
     And resolves to::
 
         "<string_1><delim><string_2><delim>..."
+
     '''
 
 
+class JoinMultiple(cfn_funcs.Join):
+    '''
+    A function for joining strings.
+
+    Takes the form::
+
+        { "list_join" : [ "<delim>", [ "<string_1>", "<string_2>", ... ] ] }
+
+    And resolves to::
+
+        "<string_1><delim><string_2><delim>..."
+
+    Optionally multiple lists may be specified, which will also be joined.
+    '''
+
+    def __init__(self, stack, fn_name, args):
+        example = '"%s" : [ " ", [ "str1", "str2"] ...]' % fn_name
+        fmt_data = {'fn_name': fn_name,
+                    'example': example}
+
+        if isinstance(args, (six.string_types, collections.Mapping)):
+            raise TypeError(_('Incorrect arguments to "%(fn_name)s" '
+                              'should be: %(example)s') % fmt_data)
+
+        try:
+            delim = args.pop(0)
+            joinlist = args.pop(0)
+        except IndexError:
+            raise ValueError(_('Incorrect arguments to "%(fn_name)s" '
+                               'should be: %(example)s') % fmt_data)
+        # Optionally allow additional lists, which are appended
+        for l in args:
+            try:
+                joinlist += l
+            except (AttributeError, TypeError):
+                raise TypeError(_('Incorrect arguments to "%(fn_name)s" '
+                                'should be: %(example)s') % fmt_data)
+        super(JoinMultiple, self).__init__(stack, fn_name,
+                                           args=[delim, joinlist])
+
+
 class ResourceFacade(cfn_funcs.ResourceFacade):
     '''
     A function for obtaining data from the facade resource from within the

heat/engine/hot/template.py

@@ -334,7 +334,7 @@ class HOTemplate20151015(HOTemplate20150430):
         'get_file': hot_funcs.GetFile,
         'get_param': hot_funcs.GetParam,
         'get_resource': cfn_funcs.ResourceRef,
-        'list_join': hot_funcs.Join,
+        'list_join': hot_funcs.JoinMultiple,
         'repeat': hot_funcs.Repeat,
         'resource_facade': hot_funcs.ResourceFacade,
         'str_replace': hot_funcs.Replace,

heat/tests/test_hot.py

@@ -49,6 +49,10 @@ hot_kilo_tpl_empty = template_format.parse('''
 heat_template_version: 2015-04-30
 ''')
 
+hot_liberty_tpl_empty = template_format.parse('''
+heat_template_version: 2015-10-15
+''')
+
 hot_tpl_empty_sections = template_format.parse('''
 heat_template_version: 2013-05-23
 parameters:
@@ -591,6 +595,37 @@ class HOTemplateTest(common.HeatTestCase):
 
         self.assertEqual(snippet_resolved, self.resolve(snippet, tmpl, stack))
 
+    def test_list_join(self):
+        snippet = {'list_join': [',', ['bar', 'baz']]}
+        snippet_resolved = 'bar,baz'
+        tmpl = template.Template(hot_kilo_tpl_empty)
+        self.assertEqual(snippet_resolved, self.resolve(snippet, tmpl))
+
+    def test_join_multiple(self):
+        snippet = {'list_join': [',', ['bar', 'baz'], ['bar2', 'baz2']]}
+        snippet_resolved = 'bar,baz,bar2,baz2'
+        tmpl = template.Template(hot_liberty_tpl_empty)
+        self.assertEqual(snippet_resolved, self.resolve(snippet, tmpl))
+
+    def test_join_invalid(self):
+        snippet = {'list_join': 'bad'}
+        tmpl = template.Template(hot_liberty_tpl_empty)
+        exc = self.assertRaises(TypeError, self.resolve, snippet, tmpl)
+        self.assertIn('Incorrect arguments', six.text_type(exc))
+
+    def test_join_invalid_value(self):
+        snippet = {'list_join': [',']}
+        tmpl = template.Template(hot_liberty_tpl_empty)
+
+        exc = self.assertRaises(ValueError, self.resolve, snippet, tmpl)
+        self.assertIn('Incorrect arguments', six.text_type(exc))
+
+    def test_join_invalid_multiple(self):
+        snippet = {'list_join': [',', 'bad', ['foo']]}
+        tmpl = template.Template(hot_liberty_tpl_empty)
+        exc = self.assertRaises(TypeError, self.resolve, snippet, tmpl)
+        self.assertIn('Incorrect arguments', six.text_type(exc))
+
     def test_repeat(self):
         """Test repeat function."""
         snippet = {'repeat': {'template': 'this is %var%',