refactor(eventsub): use variants for sum types (#5930)

lib/twitch-eventsub-ws/ast/lib/generate.py

@@ -17,6 +17,7 @@ def _generate_implementation(header_path: str, items: list[Struct | Enum]) -> st
     doc = f"""// WARNING: This file is automatically generated. Any changes will be lost.
 #include "{header_path}"
 #include "twitch-eventsub-ws/chrono.hpp" // IWYU pragma: keep
+#include "twitch-eventsub-ws/detail/variant.hpp" // IWYU pragma: keep
 #include "twitch-eventsub-ws/detail/errors.hpp"
 #include <boost/json.hpp>
 

lib/twitch-eventsub-ws/ast/lib/member.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from typing import Optional
+from dataclasses import dataclass
 
 import logging
 
@@ -54,6 +55,19 @@ def _is_trivially_copyable(type: clang.cindex.Type) -> bool:
     return _is_chrono_like_type(type)
 
 
+def _has_no_fields(type: clang.cindex.Type) -> bool:
+    for _ in type.get_fields():
+        return False
+    return True
+
+
+@dataclass
+class VariantType:
+    name: str
+    trivial: bool
+    empty: bool
+
+
 class Member:
     def __init__(
         self,
@@ -68,6 +82,8 @@ class Member:
         self.type_name = type_name
         self.tag: Optional[str] = None
         self.trivial = trivial
+        self.variant_types: list[VariantType] | None = None
+        self.variant_fallback: str | None = None
 
         self.dont_fail_on_deserialization: bool = False
 
@@ -124,7 +140,8 @@ class Member:
                                         overwrite_member_type = MemberType.OPTIONAL_VECTOR
                                     case other:
                                         log.warning(f"Vector cannot be added on top of other member type: {other}")
-
+                            case "variant":
+                                overwrite_member_type = MemberType.VARIANT
                             case other:
                                 log.warning(f"Unhandled template type: {other}")
 
@@ -144,8 +161,28 @@ class Member:
 
         member.apply_comment_commands(comment_commands)
 
+        if member.member_type == MemberType.VARIANT:
+            member.apply_variant(node.type, namespace)
+
         return member
 
+    def apply_variant(self, type: clang.cindex.Type, namespace: tuple[str, ...]):
+        self.variant_types = []
+        for idx in range(type.get_num_template_arguments()):
+            inner = type.get_template_argument_type(idx)
+            name = get_type_name(inner, namespace)
+            if name == "std::string" or name == "String":
+                assert not self.variant_fallback
+                self.variant_fallback = name
+                continue
+            self.variant_types.append(
+                VariantType(
+                    name=name,
+                    trivial=_is_trivially_copyable(inner),
+                    empty=_has_no_fields(inner),
+                )
+            )
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, self.__class__):
             return False

lib/twitch-eventsub-ws/ast/lib/membertype.py

@@ -6,3 +6,4 @@ class MemberType(Enum):
     VECTOR = 2
     OPTIONAL = 3
     OPTIONAL_VECTOR = 4
+    VARIANT = 5

lib/twitch-eventsub-ws/ast/lib/templates/field-variant.tmpl

@@ -0,0 +1,49 @@
+{% if not field.tag -%}
+static_assert(false, "{{field.name}} doesn't have a json_tag");
+{%- endif %}
+const auto *jv{{field.name}}Tag = root.if_contains("{{field.tag}}");
+if (jv{{field.name}}Tag == nullptr)
+{
+    EVENTSUB_BAIL_HERE(error::Kind::FieldMissing);
+}
+
+auto {{field.name}}TagRes = boost::json::try_value_to<boost::json::string>(*jv{{field.name}}Tag);
+if ({{field.name}}TagRes.has_error())
+{
+    return {{field.name}}TagRes.error();
+}
+std::string_view {{field.name}}Tag = *{{field.name}}TagRes;
+decltype(std::declval<{{struct.full_name}}>().{{field.name}}) {{field.name}};
+{%- for type in field.variant_types %}
+
+{%- if not loop.first %}else{% endif %} if ({{field.name}}Tag == {{type.name}}::TAG)
+{
+{%- if type.empty -%}
+    {{field.name}}.emplace<{{type.name}}>();
+{%- else -%}
+    const auto *{{field.name}}Val = root.if_contains(detail::fieldFor<{{type.name}}>());
+    if (!{{field.name}}Val)
+    {
+        EVENTSUB_BAIL_HERE(error::Kind::FieldMissing);
+    }
+    auto {{field.name}}{{type.name}} = boost::json::try_value_to<{{type.name}}>(*{{field.name}}Val);
+    if ({{field.name}}{{type.name}}.has_error())
+    {
+        return {{field.name}}{{type.name}}.error();
+    }
+    {% if type.trivial -%}
+    {{field.name}}.emplace<{{type.name}}>({{field.name}}{{type.name}}.value());
+    {%- else -%}
+    {{field.name}}.emplace<{{type.name}}>(std::move({{field.name}}{{type.name}}.value()));
+    {%- endif %}
+{%- endif -%}
+}
+{%- endfor -%}
+else
+{
+{%- if field.variant_fallback -%}
+    {{field.name}}.emplace<{{field.variant_fallback}}>({{field.name}}Tag);
+{%- else -%}
+    EVENTSUB_BAIL_HERE(error::Kind::UnknownVariant);
+{%- endif -%}
+}

lib/twitch-eventsub-ws/ast/lib/templates/initializer-variant.tmpl

@@ -0,0 +1 @@
+.{{field.name}} = std::move({{field.name}}),

lib/twitch-eventsub-ws/ast/lib/templates/struct-implementation.tmpl

@@ -1,5 +1,5 @@
 boost::json::result_for<{{struct.full_name}}, boost::json::value>::type tag_invoke(
-    boost::json::try_value_to_tag<{{struct.full_name}}> /* tag */, const boost::json::value &jvRoot)
+    boost::json::try_value_to_tag<{{struct.full_name}}> /* tag */, const boost::json::value &{%- if struct.members|length -%}jvRoot{%- else -%}/* jvRoot */{%- endif -%})
 {
     {% if struct.inner_root %}
     if (!jvRoot.is_object())
@@ -38,6 +38,8 @@ boost::json::result_for<{{struct.full_name}}, boost::json::value>::type tag_invo
     {% include 'field-optional.tmpl' indent content %}
     {%- elif field.member_type == MemberType.OPTIONAL_VECTOR -%}
     {% include 'field-optional-vector.tmpl' indent content %}
+    {%- elif field.member_type == MemberType.VARIANT -%}
+    {% include 'field-variant.tmpl' indent content %}
     {%- endif -%}
 {% endfor %}
 
@@ -51,6 +53,8 @@ boost::json::result_for<{{struct.full_name}}, boost::json::value>::type tag_invo
         {% include 'initializer-optional.tmpl' indent content %}
         {%- elif field.member_type == MemberType.OPTIONAL_VECTOR -%}
         {% include 'initializer-optional-vector.tmpl' indent content %}
+        {%- elif field.member_type == MemberType.VARIANT -%}
+        {% include 'initializer-variant.tmpl' indent content %}
         {%- endif -%}
 {% endfor %}
     };

lib/twitch-eventsub-ws/ast/lib/walker.py

@@ -68,6 +68,8 @@ class Walker:
                 if type is None:
                     # Skip nodes without a type
                     return False
+                if node.storage_class == clang.cindex.StorageClass.STATIC:
+                    return False
 
                 # log.debug(f"{struct}: {type.spelling} {node.spelling} ({type.kind})")
                 if struct: