xml: support for forwarding stream language to XSO

aioxmpp/xml.py

@@ -808,6 +808,7 @@ def __init__(self):
         self.remote_from = None
         self.remote_to = None
         self.remote_id = None
+        self.remote_lang = None
 
     @property
     def stanza_parser(self):
@@ -826,6 +827,7 @@ def stanza_parser(self, value):
         if self._state != ProcessorState.CLEAN:
             raise RuntimeError("invalid state: {}".format(self._state))
         self._stanza_parser = value
+        self._stanza_parser.lang = self.remote_lang
 
     def processingInstruction(self, target, foo):
         raise errors.StreamError(
@@ -922,6 +924,16 @@ def startElementNS(self, name, qname, attributes):
                 "id attribute required in response header"
             )
 
+        try:
+            lang = attributes.pop((namespaces.xml, "lang"))
+        except KeyError:
+            self.remote_lang = None
+        else:
+            self.remote_lang = structs.LanguageTag.fromstr(lang)
+
+        if self._stanza_parser is not None:
+            self._stanza_parser.lang = self.remote_lang
+
         if self.on_stream_header:
             self.on_stream_header()
 

tests/test_xml.py

@@ -2021,6 +2021,42 @@ class Foo(xso.XSO):
     #         cm.exception.condition
     #     )
 
+    def test_forwards_xml_lang_to_parser(self):
+        results = []
+
+        def recv(obj):
+            nonlocal results
+            results.append(obj)
+
+        class Foo(xso.XSO):
+            TAG = ("uri:foo", "foo")
+
+            attr = xso.LangAttr()
+
+        self.proc.stanza_parser = xso.XSOParser()
+        self.proc.stanza_parser.add_class(Foo, recv)
+
+        attrs = dict(self.STREAM_HEADER_ATTRS)
+        attrs[namespaces.xml, "lang"] = "en"
+
+        self.proc.startDocument()
+        self.proc.startElementNS(self.STREAM_HEADER_TAG, None,
+                                 attrs)
+
+        self.proc.startElementNS(Foo.TAG, None, {})
+        self.proc.endElementNS(Foo.TAG, None)
+
+        self.assertEqual(1, len(results))
+
+        f = results.pop()
+        self.assertEqual(
+            f.attr,
+            structs.LanguageTag.fromstr("en")
+        )
+
+        self.proc.endElementNS(self.STREAM_HEADER_TAG, None)
+        self.proc.endDocument()
+
     def tearDown(self):
         del self.proc
         del self.parser