Python protobuf: kwargs initialization now allows dict() for proto map values.

It is now possible to initialize a field of type `map<string, Message>` with nested dict objects:
```
storage_pb2.Directory(
  name='/home/user',
  owner='user',
  content={
    '.bashrc': dict(    # <=== dict() allowed here
      size=1234,
      permissions='PRIVATE',
    ),
  },
)
```

PiperOrigin-RevId: 719437601

python/google/protobuf/internal/message_test.py

@@ -2550,6 +2550,10 @@ class Proto3Test(unittest.TestCase):
     msg2 = map_unittest_pb2.TestMap(
         map_string_foreign_message=msg1.map_string_foreign_message)
     self.assertEqual(42, msg2.map_string_foreign_message['test'].c)
+    msg3 = map_unittest_pb2.TestMap(
+        map_string_foreign_message={'test': dict(c=42)}
+    )
+    self.assertEqual(42, msg3.map_string_foreign_message['test'].c)
 
   def testMapFieldRaisesCorrectError(self):
     # Should raise a TypeError when given a non-iterable.

python/google/protobuf/internal/python_message.py

@@ -523,7 +523,11 @@ def _AddInitMethod(message_descriptor, cls):
           if _IsMapField(field):
             if _IsMessageMapField(field):
               for key in field_value:
-                field_copy[key].MergeFrom(field_value[key])
+                item_value = field_value[key]
+                if isinstance(item_value, dict):
+                  field_copy[key].__init__(**item_value)
+                else:
+                  field_copy[key].MergeFrom(item_value)
             else:
               field_copy.update(field_value)
           else:

python/google/protobuf/pyext/message.cc

@@ -1001,17 +1001,32 @@ int InitAttributes(CMessage* self, PyObject* args, PyObject* kwargs) {
           if (source_value.get() == nullptr || dest_value.get() == nullptr) {
             return -1;
           }
-          ScopedPyObjectPtr ok(PyObject_CallMethod(
-              dest_value.get(), "MergeFrom", "O", source_value.get()));
-          if (ok.get() == nullptr) {
+          if (!PyObject_TypeCheck(dest_value.get(), CMessage_Type)) {
+            PyErr_Format(PyExc_SystemError,
+                         "Unexpectedly, a map of messages contains a "
+                         "non-message value: %s",
+                         Py_TYPE(dest_value.get())->tp_name);
             return -1;
           }
+          CMessage* target_message =
+              reinterpret_cast<CMessage*>(dest_value.get());
+          if (PyDict_Check(source_value.get())) {
+            if (InitAttributes(target_message, nullptr, source_value.get()) <
+                0) {
+              return -1;
+            }
+          } else {
+            ScopedPyObjectPtr ok(PyObject_CallMethod(
+                dest_value.get(), "MergeFrom", "O", source_value.get()));
+            if (ok.get() == nullptr) {
+              return -1;
+            }
+          }
         }
       } else {
-        ScopedPyObjectPtr function_return;
-        function_return.reset(
+        ScopedPyObjectPtr ok(
             PyObject_CallMethod(map.get(), "update", "O", value));
-        if (function_return.get() == nullptr) {
+        if (ok.get() == nullptr) {
           return -1;
         }
       }
@@ -1111,33 +1126,29 @@ int InitAttributes(CMessage* self, PyObject* args, PyObject* kwargs) {
             return -1;
           }
         }
-      } else {
-        if (PyObject_TypeCheck(value, CMessage_Type)) {
-          ScopedPyObjectPtr merged(MergeFrom(cmessage, value));
-          if (merged == nullptr) {
-            return -1;
-          }
-        } else {
-          if (descriptor->message_type()->well_known_type() !=
-                  Descriptor::WELLKNOWNTYPE_UNSPECIFIED &&
-              PyObject_HasAttrString(reinterpret_cast<PyObject*>(cmessage),
-                                     "_internal_assign")) {
-            AssureWritable(cmessage);
-            ScopedPyObjectPtr ok(
-                PyObject_CallMethod(reinterpret_cast<PyObject*>(cmessage),
-                                    "_internal_assign", "O", value));
-            if (ok.get() == nullptr) {
-              return -1;
-            }
-          } else {
-            PyErr_Format(PyExc_TypeError,
-                         "Parameter to initialize message field must be "
-                         "dict or instance of same class: expected %s got %s.",
-                         std::string(descriptor->full_name()).c_str(),
-                         Py_TYPE(value)->tp_name);
-            return -1;
-          }
+      } else if (PyObject_TypeCheck(value, CMessage_Type)) {
+        ScopedPyObjectPtr merged(MergeFrom(cmessage, value));
+        if (merged == nullptr) {
+          return -1;
         }
+      } else if (descriptor->message_type()->well_known_type() !=
+                     Descriptor::WELLKNOWNTYPE_UNSPECIFIED &&
+                 PyObject_HasAttrString(reinterpret_cast<PyObject*>(cmessage),
+                                        "_internal_assign")) {
+        AssureWritable(cmessage);
+        ScopedPyObjectPtr ok(
+            PyObject_CallMethod(reinterpret_cast<PyObject*>(cmessage),
+                                "_internal_assign", "O", value));
+        if (ok.get() == nullptr) {
+          return -1;
+        }
+      } else {
+        PyErr_Format(PyExc_TypeError,
+                     "Parameter to initialize message field must be "
+                     "dict or instance of same class: expected %s got %s.",
+                     std::string(descriptor->full_name()).c_str(),
+                     Py_TYPE(value)->tp_name);
+        return -1;
       }
     } else {
       ScopedPyObjectPtr new_val;

python/message.c

@@ -318,9 +318,14 @@ static bool PyUpb_Message_LookupName(PyUpb_Message* self, PyObject* py_name,
 static bool PyUpb_Message_InitMessageMapEntry(PyObject* dst, PyObject* src) {
   if (!src || !dst) return false;
 
-  PyObject* ok = PyObject_CallMethod(dst, "CopyFrom", "O", src);
-  if (!ok) return false;
-  Py_DECREF(ok);
+  if (PyDict_Check(src)) {
+    bool ok = PyUpb_Message_InitAttributes(dst, NULL, src) >= 0;
+    if (!ok) return false;
+  } else {
+    PyObject* ok = PyObject_CallMethod(dst, "CopyFrom", "O", src);
+    if (!ok) return false;
+    Py_DECREF(ok);
+  }
 
   return true;
 }