Fix trailing return type in virtual functions (react#55644)

Summary:
Pull Request resolved: react#55644

Changelog: [Internal]

Updates the C++ api snapshot generator to correctly handle trailing return types for pure virtual functions.

Reviewed By: cipolleschi

Differential Revision: D93407597

fbshipit-source-id: c0bd00752fa69eea6c75933adba7a5782a74e90d

Author: j-piasecki

scripts/cxx-api/parser/main.py

@@ -6,6 +6,7 @@
 from __future__ import annotations
 
 import os
+import re
 from pprint import pprint
 
 from doxmlparser import compound, index
@@ -246,10 +247,13 @@ def get_function_member(
     function_name = function_def.get_name()
     function_type = resolve_ref_text_name(function_def.get_type())
     function_arg_string = function_def.get_argsstring()
-    function_virtual = (
-        function_def.get_virt() == "virtual"
-        or function_def.get_virt() == "pure-virtual"
-    )
+    is_pure_virtual = function_def.get_virt() == "pure-virtual"
+    function_virtual = function_def.get_virt() == "virtual" or is_pure_virtual
+
+    # Doxygen incorrectly merges "=0" into the return type for pure-virtual
+    # functions using trailing return types (e.g. "auto f() -> T = 0").
+    # Strip the trailing "=0" from the type string.
+    function_type = re.sub(r"\s*=\s*0\s*$", "", function_type)
 
     doxygen_params = get_doxygen_params(function_def)
 
@@ -259,6 +263,7 @@ def get_function_member(
         visibility,
         function_arg_string,
         function_virtual,
+        is_pure_virtual,
         is_static,
         doxygen_params,
     )

scripts/cxx-api/parser/member.py

@@ -166,6 +166,7 @@ def __init__(
         visibility: str,
         arg_string: str,
         is_virtual: bool,
+        is_pure_virtual: bool,
         is_static: bool,
         doxygen_params: list[Argument] | None = None,
     ) -> None:
@@ -178,6 +179,12 @@ def __init__(
             doxygen_params if doxygen_params is not None else parsed_arguments
         )
 
+        # Doxygen signals pure-virtual via the virt attribute, but the arg string
+        # may not contain "= 0" (e.g. trailing return type syntax), so the
+        # modifiers parsed from the arg string may miss it. Propagate the flag.
+        if is_pure_virtual:
+            self.modifiers.is_pure_virtual = True
+
         self.is_const = self.modifiers.is_const
         self.is_override = self.modifiers.is_override
 

scripts/cxx-api/tests/snapshots/should_handle_pure_virtual_trailing_return/snapshot.api

@@ -0,0 +1,7 @@
+class test::Base {
+  public virtual const char * getName() = 0;
+  public virtual std::vector< test::Method > getMethods() = 0;
+}
+
+struct test::Method {
+}

scripts/cxx-api/tests/snapshots/should_handle_pure_virtual_trailing_return/test.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <vector>
+
+namespace test {
+
+struct Method {};
+
+class Base {
+ public:
+  virtual auto getMethods() -> std::vector<Method> = 0;
+  virtual auto getName() -> const char * = 0;
+};
+
+} // namespace test