xmlbuilder: Make clear() remove unknown XML properties

tests/xmlparse-xml/clear-cpu-unknown-vals-in.xml

@@ -0,0 +1,20 @@
+<domain type="test">
+  <name>test-cpu-unknown-clear</name>
+  <memory unit="KiB">8388608</memory>
+  <currentMemory unit="KiB">2097152</currentMemory>
+  <vcpu placement="static">2</vcpu>
+  <os>
+    <type arch="i686">hvm</type>
+    <boot dev="hd"/>
+  </os>
+  <cpu>
+    <foo bar="baz"/>
+    <blah/>
+  </cpu>
+  <clock offset="utc"/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>

tests/xmlparse-xml/clear-cpu-unknown-vals-out.xml

@@ -0,0 +1,16 @@
+<domain type="test">
+  <name>test-cpu-unknown-clear</name>
+  <memory unit="KiB">8388608</memory>
+  <currentMemory unit="KiB">2097152</currentMemory>
+  <vcpu placement="static">2</vcpu>
+  <os>
+    <type arch="i686">hvm</type>
+    <boot dev="hd"/>
+  </os>
+  <clock offset="utc"/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>

tests/xmlparse.py

@@ -1104,6 +1104,16 @@ class XMLParseTest(unittest.TestCase):
     # Misc tests #
     ##############
 
+    def testCPUUnknownClear(self):
+        # Make sure .clear() even removes XML elements we don't know about
+        basename = "clear-cpu-unknown-vals"
+        infile = "tests/xmlparse-xml/%s-in.xml" % basename
+        outfile = "tests/xmlparse-xml/%s-out.xml" % basename
+        guest = virtinst.Guest(conn, parsexml=file(infile).read())
+
+        guest.cpu.clear()
+        utils.diff_compare(guest.get_xml_config(), outfile)
+
     def testzzzzCheckProps(self):
         # pylint: disable=W0212
         # Access to protected member, needed to unittest stuff

virtinst/xmlbuilder.py

@@ -855,6 +855,9 @@ class XMLBuilder(object):
         for prop in props:
             prop.clear(self)
 
+        _remove_xpath_node(self._xmlstate.xml_ctx,
+                           self.get_root_xpath())
+
     def validate(self):
         """
         Validate any set values and raise an exception if there's