Support XML-RPC multicall

tests/unit/legacy/api/xmlrpc/test_xmlrpc.py

@@ -792,3 +792,69 @@ def test_browse(db_request):
             "Programming Language :: Python",
         ],
     )) == {(expected_release.name, expected_release.version)}
+
+
+class TestMulticall:
+
+    def test_multicall(self, monkeypatch):
+        dumped = pretend.stub(encode=lambda: None)
+        dumps = pretend.call_recorder(lambda *a, **kw: dumped)
+        monkeypatch.setattr(xmlrpc.xmlrpc.client, 'dumps', dumps)
+
+        loaded = pretend.stub()
+        loads = pretend.call_recorder(lambda *a, **kw: loaded)
+        monkeypatch.setattr(xmlrpc.xmlrpc.client, 'loads', loads)
+
+        subreq = pretend.stub()
+        blank = pretend.call_recorder(lambda *a, **kw: subreq)
+        monkeypatch.setattr(xmlrpc.Request, 'blank', blank)
+
+        body = pretend.stub()
+        response = pretend.stub(body=body)
+
+        invoke_subrequest = pretend.call_recorder(lambda *a, **kw: response)
+        request = pretend.stub(invoke_subrequest=invoke_subrequest)
+
+        args = [
+            {'methodName': 'search', 'params': [{'name': 'foo'}]},
+            {'methodName': 'browse', 'params': [{'classifiers': ['bar']}]},
+        ]
+
+        responses = xmlrpc.multicall(request, args)
+
+        assert responses == [loaded, loaded]
+        assert blank.calls == [
+            pretend.call('/RPC2', headers={'Content-Type': 'text/xml'}),
+            pretend.call('/RPC2', headers={'Content-Type': 'text/xml'}),
+        ]
+        assert invoke_subrequest.calls == [
+            pretend.call(subreq, use_tweens=True),
+            pretend.call(subreq, use_tweens=True),
+        ]
+        assert dumps.calls == [
+            pretend.call(({'name': 'foo'},), methodname='search'),
+            pretend.call(({'classifiers': ['bar']},), methodname='browse'),
+        ]
+        assert loads.calls == [pretend.call(body), pretend.call(body)]
+
+    def test_recursive_multicall(self):
+        request = pretend.stub()
+        args = [
+            {'methodName': 'system.multicall', 'params': []},
+        ]
+        with pytest.raises(xmlrpc.XMLRPCWrappedError) as exc:
+            xmlrpc.multicall(request, args)
+
+        assert exc.value.faultString == (
+            'ValueError: Cannot use system.multicall inside a multicall'
+        )
+
+    def test_missing_multicall_method(self):
+        request = pretend.stub()
+        args = [{}]
+        with pytest.raises(xmlrpc.XMLRPCWrappedError) as exc:
+            xmlrpc.multicall(request, args)
+
+        assert exc.value.faultString == (
+            'ValueError: Method name not provided'
+        )

warehouse/legacy/api/xmlrpc/views.py

@@ -13,10 +13,12 @@
 import collections.abc
 import datetime
 import functools
+import xmlrpc.client
 import xmlrpc.server
 
 from elasticsearch_dsl import Q
 from packaging.utils import canonicalize_name
+from pyramid.request import Request
 from pyramid.view import view_config
 from pyramid_rpc.xmlrpc import (
     exception_view as _exception_view, xmlrpc_method as _xmlrpc_method
@@ -441,3 +443,29 @@ def browse(request, classifiers):
     )
 
     return [(r.name, r.version) for r in releases]
+
+
+@xmlrpc_method(method='system.multicall')
+def multicall(request, args):
+    if any(arg.get('methodName') == 'system.multicall' for arg in args):
+        raise XMLRPCWrappedError(
+            ValueError('Cannot use system.multicall inside a multicall')
+        )
+
+    if not all(arg.get('methodName') for arg in args):
+        raise XMLRPCWrappedError(
+            ValueError('Method name not provided')
+        )
+
+    responses = []
+    for arg in args:
+        name = arg.get('methodName')
+        subreq = Request.blank('/RPC2', headers={'Content-Type': 'text/xml'})
+        subreq.method = 'POST'
+        subreq.body = xmlrpc.client.dumps(
+            tuple(arg.get('params')),
+            methodname=name,
+        ).encode()
+        response = request.invoke_subrequest(subreq, use_tweens=True)
+        responses.append(xmlrpc.client.loads(response.body))
+    return responses