Embind: Make subclasses inherit class functions (#18794)

Author: JeanChristopheMorinPerso

src/embind/embind.js

@@ -2047,6 +2047,15 @@ var LibraryEmbind = {
                                                   upcast,
                                                   downcast);
 
+        if (registeredClass.baseClass) {
+          // Keep track of class hierarchy. Used to allow sub-classes to inherit class functions.
+          if (registeredClass.baseClass.__derivedClasses === undefined) {
+            registeredClass.baseClass.__derivedClasses = [];
+          }
+
+          registeredClass.baseClass.__derivedClasses.push(registeredClass);
+        }
+
         var referenceConverter = new RegisteredPointer(name,
                                                        registeredClass,
                                                        true,
@@ -2353,6 +2362,16 @@ var LibraryEmbind = {
         } else {
           proto[methodName].overloadTable[argCount-1] = func;
         }
+
+        if (classType.registeredClass.__derivedClasses) {
+          for (const derivedClass of classType.registeredClass.__derivedClasses) {
+            if (!derivedClass.constructor.hasOwnProperty(methodName)) {
+              // TODO: Add support for overloads
+              derivedClass.constructor[methodName] = func;
+            }
+          }
+        }
+
         return [];
       });
       return [];

test/embind/embind.test.js

@@ -111,6 +111,12 @@ module({
             derived.delete();
         });
 
+        test("class functions are inherited in subclasses", function() {
+            assert.equal("Base", cm.Base.classFunction());
+            assert.equal("Derived", cm.Derived.classFunction());
+            assert.equal("Derived", cm.DerivedTwice.classFunction());
+        });
+
         test("calling method on unrelated class throws error", function() {
             var a = new cm.HasTwoBases;
             var e = assert.throws(cm.BindingError, function() {

test/embind/embind_test.cpp

@@ -490,6 +490,9 @@ class Base {
     int getBaseMember() {
         return baseMember;
     }
+    static std::string classFunction() {
+        return "Base";
+    };
     std::string name;
     int member;
     int baseMember;
@@ -546,6 +549,9 @@ class Derived : public Base{
     int getMember() {
         return member;
     }
+    static std::string classFunction() {
+        return "Derived";
+    }
     int member;
 private:
     std::string name_;
@@ -2019,6 +2025,7 @@ EMSCRIPTEN_BINDINGS(tests) {
         .function("getMember", &Derived::getMember)
         .function("setMember", &Derived::setMember)
         .property("member", &Derived::member)
+        .class_function("classFunction", &Derived::classFunction)
         ;
 
     class_<Base>("Base")
@@ -2033,6 +2040,7 @@ EMSCRIPTEN_BINDINGS(tests) {
         .function("setBaseMember", &Base::setBaseMember)
         .property("member", &Base::member)
         .property("baseMember", &Base::baseMember)
+        .class_function("classFunction", &Base::classFunction)
         ;
 
     class_<SecondBase>("SecondBase")