Allow mergers to take options.

4 files changed, 59 insertions, 30 deletions

diff --git a/cloudinit/mergers/__init__.py b/cloudinit/mergers/__init__.py
index b3e728b0..20658edc 100644
--- a/cloudinit/mergers/__init__.py
+++ b/cloudinit/mergers/__init__.py
@@ -16,11 +16,14 @@
 #    You should have received a copy of the GNU General Public License
 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import re
 
 from cloudinit import importer
 from cloudinit import log as logging
 from cloudinit import util
 
+NAME_MTCH = re.compile(r"(^[a-zA-Z_][A-Za-z0-9_]*)\((.*?)\)$")
+
 LOG = logging.getLogger(__name__)
 
 
@@ -71,10 +74,8 @@ def _extract_merger_names(merge_how):
     names = []
     for m_name in merge_how.split("+"):
         # Canonicalize the name (so that it can be found
-        # even when users alter it in various ways...
+        # even when users alter it in various ways)
         m_name = m_name.lower().strip()
-        m_name = m_name.replace(" ", "_")
-        m_name = m_name.replace("\t", "_")
         m_name = m_name.replace("-", "_")
         if not m_name:
             continue
@@ -82,23 +83,29 @@ def _extract_merger_names(merge_how):
     return names
 
 
-def construct(merge_how, default_classes=None):
-    mergers = []
-    merger_classes = []
-    root = LookupMerger(mergers)
-    for m_name in _extract_merger_names(merge_how):
+def construct(merge_how):
+    mergers_to_be = []
+    for name in _extract_merger_names(merge_how):
+        match = NAME_MTCH.match(name)
+        if not match:
+            msg = "Matcher identifer '%s' is not in the right format" % (name)
+            raise ValueError(msg)
+        (m_name, m_ops) = match.groups()
+        m_ops = m_ops.strip().split(",")
+        m_ops = [m.strip().lower() for m in m_ops if m.strip()]
         merger_locs = importer.find_module(m_name,
                                            [__name__],
                                            ['Merger'])
         if not merger_locs:
-            msg = "Could not find merger named %s" % (m_name)
+            msg = "Could not find merger named '%s'" % (m_name)
             raise ImportError(msg)
         else:
             mod = importer.import_module(merger_locs[0])
-            cls = getattr(mod, 'Merger')
-            merger_classes.append(cls)
-    if not merger_classes and default_classes:
-        merger_classes = default_classes
-    for m_class in merger_classes:
-        mergers.append(m_class(root))
+            mod_attr = getattr(mod, 'Merger')
+            mergers_to_be.append((mod_attr, m_ops))
+    # Now form them...
+    mergers = []
+    root = LookupMerger(mergers)
+    for (attr, opts) in mergers_to_be:
+        mergers.append(attr(root, opts))
     return root
\ No newline at end of file
diff --git a/cloudinit/mergers/dict.py b/cloudinit/mergers/dict.py
index a0ffaa33..e7073bd9 100644
--- a/cloudinit/mergers/dict.py
+++ b/cloudinit/mergers/dict.py
@@ -18,8 +18,12 @@
 
 
 class Merger(object):
-    def __init__(self, merger):
+    def __init__(self, merger, opts):
         self._merger = merger
+        self._overwrite = 'overwrite' in opts
+        
+        if opts and opts.lower().find("overwrite") != -1:
+            self._overwrite = True
 
     def _on_dict(self, value, merge_with):
         if not isinstance(merge_with, (dict)):
@@ -27,7 +31,10 @@ class Merger(object):
         merged = dict(value)
         for (k, v) in merge_with.items():
             if k in merged:
-                merged[k] = self._merger.merge(merged[k], v)
+                if not self._overwrite:
+                    merged[k] = self._merger.merge(merged[k], v)
+                else:
+                    merged[k] = v
             else:
                 merged[k] = v
         return merged
diff --git a/cloudinit/mergers/list.py b/cloudinit/mergers/list.py
index ad1b9793..0c65d053 100644
--- a/cloudinit/mergers/list.py
+++ b/cloudinit/mergers/list.py
@@ -18,8 +18,10 @@
 
 
 class Merger(object):
-    def __init__(self, merger):
+    def __init__(self, merger, opts):
         self._merger = merger
+        self._discard_non = 'discard_non_list' in opts
+        self._append = 'append' in opts
 
     def _on_tuple(self, value, merge_with):
         return self._on_list(list(value), merge_with)
@@ -27,15 +29,22 @@ class Merger(object):
     def _on_list(self, value, merge_with):
         if isinstance(merge_with, (tuple, list)):
             new_value = list(value)
-            for m_v in merge_with:
-                m_am = 0
-                for (i, o_v) in enumerate(new_value):
-                    if m_v == o_v:
-                        new_value[i] = self._merger.merge(o_v, m_v)
-                        m_am += 1
-                if m_am == 0:
-                    new_value.append(m_v)
+            if self._append:
+                new_value.extend(merge_with)
+            else:
+                # Merge instead
+                for m_v in merge_with:
+                    m_am = 0
+                    for (i, o_v) in enumerate(new_value):
+                        if m_v == o_v:
+                            new_value[i] = self._merger.merge(o_v, m_v)
+                            m_am += 1
+                    if m_am == 0:
+                        new_value.append(m_v)
         else:
             new_value = list(value)
-            new_value.append(merge_with)
+            if self._discard_non:
+                pass
+            else:
+                new_value.append(merge_with)
         return new_value
diff --git a/cloudinit/mergers/str.py b/cloudinit/mergers/str.py
index 7c3fa585..14bc46ec 100644
--- a/cloudinit/mergers/str.py
+++ b/cloudinit/mergers/str.py
@@ -18,11 +18,17 @@
 
 
 class Merger(object):
-    def __init__(self, merger):
-        pass
+    def __init__(self, merger, opts):
+        self._append = 'append' in opts
 
     def _on_unicode(self, value, merge_with):
         return self._on_str(value, merge_with)
 
     def _on_str(self, value, merge_with):
-        return value
+        if not self._append:
+            return value
+        else:
+            if isinstance(value, (unicode)):
+                return value + unicode(merge_with)
+            else:
+                return value + str(merge_with)