perf: collisions don't contain reserved names by default

The 'collisions' set does NOT contain RESERVED_NAMES; they are
combined at runtime when needed.

For a large real-world, this results in an order of magnitude
reduction in memory usage.
I'm not joking: Google Ads v5 uses 2.45 GB before this change
and 223 MB after.

Author: software-dov

gapic/schema/metadata.py

@@ -49,9 +49,6 @@ class Address:
     )
     collisions: FrozenSet[str] = dataclasses.field(default_factory=frozenset)
 
-    def __post_init__(self):
-        super().__setattr__("collisions", self.collisions | RESERVED_NAMES)
-
     def __eq__(self, other) -> bool:
         return all([getattr(self, i) == getattr(other, i) for i
                     in ('name', 'module', 'module_path', 'package', 'parent')])
@@ -114,7 +111,7 @@ def module_alias(self) -> str:
         while still providing names that are fundamentally readable
         to users (albeit looking auto-generated).
         """
-        if self.module in self.collisions:
+        if self.module in self.collisions | RESERVED_NAMES:
             return '_'.join(
                 (
                     ''.join(
@@ -283,7 +280,7 @@ def with_context(self, *, collisions: FrozenSet[str]) -> 'Address':
         ``Address`` object aliases module names to avoid naming collisions in
         the file being written.
         """
-        return dataclasses.replace(self, collisions=frozenset(collisions))
+        return dataclasses.replace(self, collisions=collisions)
 
 
 @dataclasses.dataclass(frozen=True)

gapic/schema/wrappers.py

@@ -314,13 +314,19 @@ def recursive_field_types(self) -> Sequence[
         return tuple(types)
 
     @utils.cached_property
-    def recursive_fields(self) -> FrozenSet[Field]:
-        return frozenset(chain(
+    def recursive_resource_fields(self) -> FrozenSet[Field]:
+        all_fields = chain(
             self.fields.values(),
             (field
              for t in self.recursive_field_types if isinstance(t, MessageType)
              for field in t.fields.values()),
-        ))
+        )
+        return frozenset(
+            f
+            for f in all_fields
+            if (f.options.Extensions[resource_pb2.resource_reference].type or
+                f.options.Extensions[resource_pb2.resource_reference].child_type)
+        )
 
     @property
     def map(self) -> bool:
@@ -1060,7 +1066,7 @@ def gen_resources(message):
                     yield type_
 
         def gen_indirect_resources_used(message):
-            for field in message.recursive_fields:
+            for field in message.recursive_resource_fields:
                 resource = field.options.Extensions[
                     resource_pb2.resource_reference]
                 resource_type = resource.type or resource.child_type