xmlbuilder: Allow classes to specify order of certain xml elements

This will save us some test case churn. As an example, we now
do auto building of disk <target> XML and it doesn't alter things.
Without this bus and target are often swapped.

tests/cli-test-xml/compare/many-devices.xml

@@ -23,17 +23,17 @@
   <devices>
     <emulator>/usr/bin/test-hv</emulator>
     <disk type="file" device="disk">
+      <driver cache="writeback" io="threads"/>
       <source file="/default-pool/UPPER"/>
       <target dev="hda" bus="ide"/>
       <shareable/>
       <serial>WD-WMAP9A966149</serial>
-      <driver cache="writeback" io="threads"/>
     </disk>
     <disk type="file" device="disk">
+      <driver error_policy="enospace"/>
       <source file="/tmp/__virtinst_cli_new1.img"/>
       <target dev="hdb" bus="ide"/>
       <readonly/>
-      <driver error_policy="enospace"/>
     </disk>
     <disk type="block" device="cdrom">
       <target dev="sda" bus="sata"/>
@@ -110,17 +110,17 @@
   <devices>
     <emulator>/usr/bin/test-hv</emulator>
     <disk type="file" device="disk">
+      <driver cache="writeback" io="threads"/>
       <source file="/default-pool/UPPER"/>
       <target dev="hda" bus="ide"/>
       <shareable/>
       <serial>WD-WMAP9A966149</serial>
-      <driver cache="writeback" io="threads"/>
     </disk>
     <disk type="file" device="disk">
+      <driver error_policy="enospace"/>
       <source file="/tmp/__virtinst_cli_new1.img"/>
       <target dev="hdb" bus="ide"/>
       <readonly/>
-      <driver error_policy="enospace"/>
     </disk>
     <disk type="block" device="cdrom">
       <target dev="sda" bus="sata"/>

tests/utils.py

@@ -157,6 +157,7 @@ def read_file(filename):
 def diff_compare(actual_out, filename=None, expect_out=None):
     """Compare passed string output to contents of filename"""
     if not expect_out:
+        #file(filename, "w").write(actual_out)
         expect_out = read_file(filename)
 
     diff = "".join(difflib.unified_diff(expect_out.splitlines(1),

virtinst/VirtualDisk.py

@@ -388,10 +388,14 @@ class VirtualDisk(VirtualDevice):
         except Exception, e:
             raise ValueError(_("Couldn't lookup volume object: %s" % str(e)))
 
-    _DEFAULT_SENTINEL = -1234
+
+    _XMLELEMENTORDER = ["driver", "source", "target"]
+    _XMLPROPORDER = ["target", "bus"]
+
     def __init__(self, conn, parsexml=None, parsexmlnode=None):
         VirtualDevice.__init__(self, conn, parsexml, parsexmlnode)
 
+        self._DEFAULT_SENTINEL = -1234
         self._device = self.DEVICE_DISK
         self._type = self._DEFAULT_SENTINEL
         self._driverName = self._DEFAULT_SENTINEL
@@ -756,8 +760,6 @@ class VirtualDisk(VirtualDevice):
         if path is not None:
             ret += "      <source %s='%s'/>\n" % (typeattr, path)
 
-        ret += "      <target dev='%s'/>\n" % (self.target)
-
         addr = self.indent(self.address.get_xml_config(), 6)
         if addr:
             ret += addr

virtinst/xmlbuilder.py

@@ -521,6 +521,12 @@ class XMLBuilder(object):
             xml += " " * level + l + "\n"
         return xml
 
+    # Specify a list of tag values here and we will arrange them when
+    # outputing XML. They will be put before every other element. This
+    # is strictly to keep test suite happy.
+    _XMLELEMENTORDER = []
+    _XMLPROPORDER = []
+
     _dumpxml_xpath = "."
     def __init__(self, conn, parsexml=None, parsexmlnode=None):
         """
@@ -596,10 +602,20 @@ class XMLBuilder(object):
         if not self._propstore or self._is_parse():
             return xml
 
+        do_order = []
+        proporder = self._proporder[:]
+        propstore = self._propstore.copy()
+
+        for key in self._XMLPROPORDER:
+            if key in proporder:
+                proporder.remove(key)
+                do_order.append(key)
+        proporder = do_order + proporder
+
         try:
             self._parsexml(xml, None)
-            for key in self._proporder[:]:
-                setattr(self, key, self._propstore[key])
+            for key in proporder:
+                setattr(self, key, propstore[key])
             ret = self.get_xml_config()
             for c in xml:
                 if c != " ":
@@ -627,6 +643,37 @@ class XMLBuilder(object):
         """
         raise NotImplementedError()
 
+    def _order_xml_elements(self, xml):
+        # This whole thing is reeeally hacky but it saves us some
+        # unittest churn.
+        if not self._XMLELEMENTORDER:
+            return xml
+
+        split = xml.splitlines()
+        if len(split) < 3:
+            return xml
+
+        head = split[0]
+        end = split[-1]
+        split = split[1:-1]
+
+        baseindent = 0
+        for i in head:
+            if i != " ":
+                break
+            baseindent += 1
+
+        neworder = []
+        for prio in reversed(self._XMLELEMENTORDER):
+            tag = "%s<%s " % ((baseindent + 2) * " ", prio)
+            for idx in range(len(split)):
+                if split[idx].startswith(tag):
+                    neworder.insert(0, split.pop(idx))
+                    break
+        neworder += split
+
+        return "\n".join([head] + neworder + [end])
+
     def get_xml_config(self, *args, **kwargs):
         """
         Construct and return object xml
@@ -637,7 +684,10 @@ class XMLBuilder(object):
         if self._xml_ctx:
             node = _get_xpath_node(self._xml_ctx, self._dumpxml_xpath)
             if not node:
-                return ""
-            return _sanitize_libxml_xml(node.serialize())
+                ret = ""
+            else:
+                ret = _sanitize_libxml_xml(node.serialize())
+        else:
+            ret = self._get_xml_config(*args, **kwargs)
 
-        return self._get_xml_config(*args, **kwargs)
+        return self._order_xml_elements(ret)