Patch #103885: Add dynamic registration and lookup of DOM implementations.
diff --git a/Lib/xml/dom/domreg.py b/Lib/xml/dom/domreg.py
new file mode 100644
index 0000000..14b87d6
--- /dev/null
+++ b/Lib/xml/dom/domreg.py
@@ -0,0 +1,76 @@
+"""Registration facilities for DOM. This module should not be used
+directly. Instead, the functions getDOMImplementation and
+registerDOMImplementation should be imported from xml.dom."""
+
+# This is a list of well-known implementations. Well-known names
+# should be published by posting to xml-sig@python.org, and are
+# subsequently recorded in this file.
+
+well_known_implementations = {
+ 'minidom':'xml.dom.minidom',
+ '4DOM': 'xml.dom.DOMImplementation',
+ }
+
+# DOM implementations not officially registered should register
+# themselves with their
+
+registered = {}
+
+def registerDOMImplementation(name, factory):
+ """registerDOMImplementation(name, factory)
+
+ Register the factory function with the name. The factory function
+ should return an object which implements the DOMImplementation
+ interface. The factory function can either return the same object,
+ or a new one (e.g. if that implementation supports some
+ customization)."""
+
+ registered[name] = factory
+
+def _good_enough(dom, features):
+ "_good_enough(dom, features) -> Return 1 if the dom offers the features"
+ for f,v in features:
+ if not dom.hasFeature(f,v):
+ return 0
+ return 1
+
+def getDOMImplementation(name = None, features = ()):
+ """getDOMImplementation(name = None, features = ()) -> DOM implementation.
+
+ Return a suitable DOM implementation. The name is either
+ well-known, the module name of a DOM implementation, or None. If
+ it is not None, imports the corresponding module and returns
+ DOMImplementation object if the import succeeds.
+
+ If name is not given, consider the available implementations to
+ find one with the required feature set. If no implementation can
+ be found, raise an ImportError. The features list must be a sequence
+ of (feature, version) pairs which are passed to hasFeature."""
+
+ import os
+ creator = None
+ mod = well_known_implementations.get(name)
+ if mod:
+ mod = __import__(mod, {}, {}, ['getDOMImplementation'])
+ return mod.getDOMImplementation()
+ elif name:
+ return registered[name]()
+ elif os.environ.has_key("PYTHON_DOM"):
+ return getDOMImplementation(name = os.environ["PYTHON_DOM"])
+
+ # User did not specify a name, try implementations in arbitrary
+ # order, returning the one that has the required features
+ for creator in registered.values():
+ dom = creator()
+ if _good_enough(dom, features):
+ return dom
+
+ for creator in well_known_implementations.keys():
+ try:
+ dom = getDOMImplementation(name = creator)
+ except StandardError: # typically ImportError, or AttributeError
+ continue
+ if _good_enough(dom, features):
+ return dom
+
+ raise ImportError,"no suitable DOM implementation found"