Keep the original dict insertion order in Py3.6+ when setting attributes or namespaces from a user provided dict.

This follows the ElementTree change in Py3.8, see https://bugs.python.org/issue34160.

2 files changed, 15 insertions, 4 deletions

diff --git a/src/lxml/apihelpers.pxi b/src/lxml/apihelpers.pxi
index cf932d43..5d410e60 100644
--- a/src/lxml/apihelpers.pxi
+++ b/src/lxml/apihelpers.pxi
@@ -244,6 +244,10 @@ cdef _iter_nsmap(nsmap):
     The difference to _iter_attrib() is that None doesn't sort with strings
     in Py3.x.
     """
+    if python.PY_VERSION_HEX >= 0x03060000:
+        # dicts are insertion-ordered in Py3.6+ => keep the user provided order.
+        if isinstance(nsmap, dict):
+            return nsmap.items()
     if len(nsmap) <= 1:
         return nsmap.items()
     # nsmap will usually be a plain unordered dict => avoid type checking overhead
@@ -271,7 +275,10 @@ cdef _iter_attrib(attrib):
     Tries to preserve an existing order and sorts if it assumes no order.
     """
     # attrib will usually be a plain unordered dict
-    if type(attrib) is dict:
+    if isinstance(attrib, dict):
+        if python.PY_VERSION_HEX >= 0x03060000:
+            # dicts are insertion-ordered in Py3.6+ => keep the user provided order.
+            return attrib.items()
         return sorted(attrib.items())
     elif isinstance(attrib, (_Attrib, OrderedDict)):
         return attrib.items()
@@ -292,8 +299,12 @@ cdef _initNodeAttributes(xmlNode* c_node, _Document doc, attrib, dict extra):
     is_html = doc._parser._for_html
     seen = set()
     if extra:
-        for name, value in sorted(extra.items()):
-            _addAttributeToNode(c_node, doc, is_html, name, value, seen)
+        if python.PY_VERSION_HEX >= 0x03060000:
+            for name, value in extra.items():
+                _addAttributeToNode(c_node, doc, is_html, name, value, seen)
+        else:
+            for name, value in sorted(extra.items()):
+                _addAttributeToNode(c_node, doc, is_html, name, value, seen)
     if attrib:
         for name, value in _iter_attrib(attrib):
             _addAttributeToNode(c_node, doc, is_html, name, value, seen)
diff --git a/src/lxml/objectify.pyx b/src/lxml/objectify.pyx
index f5fe7b51..9da49a1c 100644
--- a/src/lxml/objectify.pyx
+++ b/src/lxml/objectify.pyx
@@ -1327,7 +1327,7 @@ cdef object _dump(_Element element, int indent):
     result = f"{indentstr}{element.tag} = {value} [{_typename(element)}]\n"
     xsi_ns    = u"{%s}" % XML_SCHEMA_INSTANCE_NS
     pytype_ns = u"{%s}" % PYTYPE_NAMESPACE
-    for name, value in cetree.iterattributes(element, 3):
+    for name, value in sorted(cetree.iterattributes(element, 3)):
         if u'{' in name:
             if name == PYTYPE_ATTRIBUTE:
                 if value == TREE_PYTYPE_NAME: