fix: modules referenced in MapField message type are properly aliased

This was noticed when attempting to generate Bigtable Admin in a
message definition: an imported module is given an alias to prevent
collision with a field name. When the module is referenced to describe
the type of a singleton field it is properly disambiguated. When used
to describe the type of a MapField it is _not_ disambiguated.

Fix for that.

Closes googleapis#618

gapic/schema/metadata.py

@@ -90,6 +90,20 @@ def __str__(self) -> str:
         # Return the Python identifier.
         return '.'.join(self.parent + (self.name,))
 
+    def __repr__(self) -> str:
+        return "({})".format(
+            ", ".join(
+                (
+                    self.name,
+                    self.module,
+                    str(self.module_path),
+                    str(self.package),
+                    str(self.parent),
+                    str(self.api_naming),
+                )
+            )
+        )
+
     @property
     def module_alias(self) -> str:
         """Return an appropriate module alias if necessary.

gapic/schema/wrappers.py

@@ -222,7 +222,12 @@ def type(self) -> Union['MessageType', 'EnumType', 'PrimitiveType']:
         raise TypeError(f'Unrecognized protobuf type: {self.field_pb.type}. '
                         'This code should not be reachable; please file a bug.')
 
-    def with_context(self, *, collisions: FrozenSet[str]) -> 'Field':
+    def with_context(
+            self,
+            *,
+            collisions: FrozenSet[str],
+            visited_messages: FrozenSet["MessageType"],
+    ) -> 'Field':
         """Return a derivative of this field with the provided context.
 
         This method is used to address naming collisions. The returned
@@ -233,7 +238,8 @@ def with_context(self, *, collisions: FrozenSet[str]) -> 'Field':
             self,
             message=self.message.with_context(
                 collisions=collisions,
-                skip_fields=True,
+                skip_fields=self.message in visited_messages,
+                visited_messages=visited_messages,
             ) if self.message else None,
             enum=self.enum.with_context(collisions=collisions)
             if self.enum else None,
@@ -406,7 +412,10 @@ def get_field(self, *field_path: str,
 
         # Base case: If this is the last field in the path, return it outright.
         if len(field_path) == 1:
-            return cursor.with_context(collisions=collisions)
+            return cursor.with_context(
+                collisions=collisions,
+                visited_messages=frozenset({self}),
+            )
 
         # Sanity check: If cursor is a repeated field, then raise an exception.
         # Repeated fields are only permitted in the terminal position.
@@ -433,6 +442,7 @@ def get_field(self, *field_path: str,
     def with_context(self, *,
                      collisions: FrozenSet[str],
                      skip_fields: bool = False,
+                     visited_messages: FrozenSet["MessageType"] = frozenset(),
                      ) -> 'MessageType':
         """Return a derivative of this message with the provided context.
 
@@ -444,10 +454,14 @@ def with_context(self, *,
         underlying fields. This provides for an "exit" in the case of circular
         references.
         """
+        visited_messages = visited_messages | {self}
         return dataclasses.replace(
             self,
             fields=collections.OrderedDict(
-                (k, v.with_context(collisions=collisions))
+                (k, v.with_context(
+                    collisions=collisions,
+                    visited_messages=visited_messages
+                ))
                 for k, v in self.fields.items()
             ) if not skip_fields else self.fields,
             nested_enums=collections.OrderedDict(
@@ -457,7 +471,9 @@ def with_context(self, *,
             nested_messages=collections.OrderedDict(
                 (k, v.with_context(
                     collisions=collisions,
-                    skip_fields=skip_fields,))
+                    skip_fields=skip_fields,
+                    visited_messages=visited_messages,
+                ))
                 for k, v in self.nested_messages.items()),
             meta=self.meta.with_context(collisions=collisions),
         )

tests/unit/schema/test_api.py

@@ -1214,3 +1214,76 @@ def test_resources_referenced_but_not_typed(reference_attr="type"):
 
 def test_resources_referenced_but_not_typed_child_type():
     test_resources_referenced_but_not_typed("child_type")
+
+
+def test_map_field_name_disambiguation():
+    squid_file_pb = descriptor_pb2.FileDescriptorProto(
+        name="mollusc.proto",
+        package="animalia.mollusca.v2",
+        message_type=(
+            descriptor_pb2.DescriptorProto(
+                name="Mollusc",
+            ),
+        ),
+    )
+    method_types_file_pb = descriptor_pb2.FileDescriptorProto(
+        name="mollusc_service.proto",
+        package="animalia.mollusca.v2",
+        message_type=(
+            descriptor_pb2.DescriptorProto(
+                name="CreateMolluscRequest",
+                field=(
+                    descriptor_pb2.FieldDescriptorProto(
+                        name="mollusc",
+                        type="TYPE_MESSAGE",
+                        type_name=".animalia.mollusca.v2.Mollusc",
+                        number=1,
+                    ),
+                    descriptor_pb2.FieldDescriptorProto(
+                        name="molluscs_map",
+                        type="TYPE_MESSAGE",
+                        number=2,
+                        type_name=".animalia.mollusca.v2.CreateMolluscRequest.MolluscsMapEntry",
+                        label="LABEL_REPEATED",
+                    ),
+                ),
+                nested_type=(
+                    descriptor_pb2.DescriptorProto(
+                        name="MolluscsMapEntry",
+                        field=(
+                            descriptor_pb2.FieldDescriptorProto(
+                                name="key",
+                                type="TYPE_STRING",
+                                number=1,
+                            ),
+                            descriptor_pb2.FieldDescriptorProto(
+                                name="value",
+                                type="TYPE_MESSAGE",
+                                number=2,
+                                # We use the same type for the map value as for
+                                # the singleton above to better highlight the
+                                # problem raised in
+                                # https://github.com/googleapis/gapic-generator-python/issues/618.
+                                # The module _is_ disambiguated for singleton
+                                # fields but NOT for map fields.
+                                type_name=".animalia.mollusca.v2.Mollusc"
+                            ),
+                        ),
+                        options=descriptor_pb2.MessageOptions(map_entry=True),
+                    ),
+                ),
+            ),
+        ),
+    )
+    my_api = api.API.build(
+        file_descriptors=[squid_file_pb, method_types_file_pb],
+    )
+    create = my_api.messages['animalia.mollusca.v2.CreateMolluscRequest']
+    mollusc = create.fields['mollusc']
+    molluscs_map = create.fields['molluscs_map']
+    mollusc_ident = str(mollusc.type.ident)
+    mollusc_map_ident = str(molluscs_map.message.fields['value'].type.ident)
+
+    # The same module used in the same place should have the same import alias.
+    # Because there's a "mollusc" name used, the import should be disambiguated.
+    assert mollusc_ident == mollusc_map_ident == "am_mollusc.Mollusc"