implement flat-name container support

Summary:
Implement support for flat-name containers in py3 auto-migrate.

Previously, `import List__i32 from foo.types` would hard crash. Now it returns a class based loosely on `python.types.ListTypeFactory(typeinfo_i32)`. The class extends `python.types.List` and supplies the necessary `typeinfo` to properly construct `List`. It forwards the values, whether passed as `args` or `kwargs`.

The class uses a `metaclass` that implements `__instancecheck__` so that customer `isinstance(x, List__i32)` will work properly even in auto-migrate.

Reviewed By: prakashgayasen, Filip-F

Differential Revision: D66985311

fbshipit-source-id: f4aa70084676f0617daa17768069f2df85080718

thrift/compiler/generate/t_mstch_py3_generator.cc

@@ -601,6 +601,8 @@ class py3_mstch_type : public mstch_type {
         this,
         {
             {"type:modulePath", &py3_mstch_type::modulePath},
+            {"type:module_auto_migrate_path",
+             &py3_mstch_type::moduleAutoMigratePath},
             {"type:cbinding_path", &py3_mstch_type::cbinding_path},
             {"type:flat_name", &py3_mstch_type::flatName},
             {"type:cppNamespaces", &py3_mstch_type::cppNamespaces},
@@ -651,6 +653,13 @@ class py3_mstch_type : public mstch_type {
             get_type_py3_namespace(get_type_program(), "cbindings"), "_"));
   }
 
+  mstch::node moduleAutoMigratePath() {
+    return fmt::format(
+        "_{}",
+        fmt::join(
+            get_type_py3_namespace(get_type_program(), "thrift_types"), "_"));
+  }
+
   mstch::node flatName() { return cached_props_.flat_name(); }
 
   mstch::node cppNamespaces() {

thrift/compiler/generate/templates/py3/types.py.mustache

@@ -35,4 +35,51 @@ want to include.
 {{#program:auto_migrate?}}
 {{> common/auto_generated_py}}
 from {{#program:py3Namespaces}}{{value}}.{{/program:py3Namespaces}}{{program:name}}.thrift_types import *
+{{#program:hasContainerTypes}}
+import thrift.python.types as _fbthrift_python_types
+import {{#program:py3Namespaces}}{{value}}.{{/program:py3Namespaces}}{{program:name}}.thrift_types as {{!
+}}_{{#program:py3Namespaces}}{{value}}_{{/program:py3Namespaces}}{{program:name}}_thrift_types
+{{#program:includeNamespaces}}
+{{#hasTypes?}}
+import {{#includeNamespace}}{{value}}.{{/includeNamespace}}thrift_types as _{{#includeNamespace}}{{value}}_{{/includeNamespace}}thrift_types
+{{/hasTypes?}}
+{{/program:includeNamespaces}}
+{{/program:hasContainerTypes}}{{!
+
+py3-container "flat name" name aliases for backwards-compatibility
+
+}}
+{{#program:containerTypes}}
+{{#type:container?}}
+class {{type:flat_name}}__Meta(type):
+    def _fbthrift_type_info(cls):
+        return (
+        {{#type:list?}}
+            {{#type:list_elem_type}}{{> types/typeinfo }}{{/type:list_elem_type}},
+        {{/type:list?}}
+        {{#type:set?}}
+            {{#type:set_elem_type}}{{> types/typeinfo }}{{/type:set_elem_type}},
+        {{/type:set?}}
+        {{#type:map?}}
+            {{#type:key_type}}{{> types/typeinfo }}{{/type:key_type}},
+            {{#type:value_type}}{{> types/typeinfo }}{{/type:value_type}},
+        {{/type:map?}}
+        )
+
+    def __instancecheck__(cls, instance):
+        return (
+            isinstance(instance, _fbthrift_python_types.{{> types/container_base}}) and
+            instance._fbthrift_same_type(*cls._fbthrift_type_info())
+        )
+
+class {{type:flat_name}}(_fbthrift_python_types.{{> types/container_base}}, metaclass={{type:flat_name}}__Meta):
+    def __init__(self, *args, **kwargs):
+        super().__init__(
+            *{{type:flat_name}}._fbthrift_type_info(),
+            *args,
+            **kwargs,
+        )
+
+{{/type:container?}}
+{{/program:containerTypes}}
 {{/program:auto_migrate?}}

thrift/compiler/generate/templates/py3/types/container_base.mustache

@@ -0,0 +1,24 @@
+{{!
+
+  Copyright (c) Meta Platforms, Inc. and affiliates.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+}}{{!
+
+This is used only in py3 auto-migrate for the base class
+of flat-name containers (List__i32)
+
+}}{{#type:list?}}List{{/type:list?}}{{!
+}}{{#type:set?}}Set{{/type:set?}}{{!
+}}{{#type:map?}}Map{{/type:map?}}

thrift/compiler/generate/templates/py3/types/typeinfo.mustache

@@ -0,0 +1,42 @@
+{{!
+
+  Copyright (c) Meta Platforms, Inc. and affiliates.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+}}{{!
+
+This is used only in py3 auto-migrate to generate
+aliases for container flat names, i.e., List__i32
+
+}}{{#type:bool?}}_fbthrift_python_types.typeinfo_bool{{/type:bool?}}{{!
+}}{{#type:byte?}}_fbthrift_python_types.typeinfo_byte{{/type:byte?}}{{!
+}}{{#type:i16?}}_fbthrift_python_types.typeinfo_i16{{/type:i16?}}{{!
+}}{{#type:i32?}}_fbthrift_python_types.typeinfo_i32{{/type:i32?}}{{!
+}}{{#type:i64?}}_fbthrift_python_types.typeinfo_i64{{/type:i64?}}{{!
+}}{{#type:double?}}_fbthrift_python_types.typeinfo_double{{/type:double?}}{{!
+}}{{#type:float?}}_fbthrift_python_types.typeinfo_float{{/type:float?}}{{!
+}}{{#type:string?}}_fbthrift_python_types.typeinfo_string{{/type:string?}}{{!
+}}{{#type:binary?}}{{#type:iobuf?}}_fbthrift_python_types.typeinfo_iobuf{{/type:iobuf?}}{{^type:iobuf?}}_fbthrift_python_types.typeinfo_binary{{/type:iobuf?}}{{/type:binary?}}{{!
+}}{{#type:struct}}_fbthrift_python_types.StructTypeInfo({{!
+  }}{{type:module_auto_migrate_path}}.{{struct:name}}){{!
+}}{{/type:struct}}{{!
+}}{{#type:list?}}_fbthrift_python_types.ListTypeInfo({{#type:list_elem_type}}{{> types/typeinfo }}{{/type:list_elem_type}}){{/type:list?}}{{!
+}}{{#type:set?}}_fbthrift_python_types.SetTypeInfo({{#type:set_elem_type}}{{> types/typeinfo }}{{/type:set_elem_type}}){{/type:set?}}{{!
+}}{{#type:map?}}_fbthrift_python_types.MapTypeInfo({{!
+  }}{{#type:key_type}}{{> types/typeinfo }}{{/type:key_type}}, {{!
+  }}{{#type:value_type}}{{> types/typeinfo }}{{/type:value_type}}{{!
+}}){{/type:map?}}{{!
+}}{{#type:enum}}_fbthrift_python_types.EnumTypeInfo({{!
+  }}{{type:module_auto_migrate_path}}.{{enum:name}}){{!
+}}{{/type:enum}}