Berry allow setmember() to fail with false or undefined

lib/libesp32/berry/src/be_class.c

@@ -339,6 +339,20 @@ bbool be_instance_setmember(bvm *vm, binstance *o, bstring *name, bvalue *src)
             vm->top += 4;   /* prevent collection results */
             be_dofunc(vm, top, 3); /* call method 'member' */
             vm->top -= 4;
+            /* if return value is `false` or `undefined` signal an unknown attribute */
+            int type = var_type(vm->top);
+            if (type == BE_BOOL) {
+                bbool ret = var_tobool(vm->top);
+                if (!ret) {
+                    return bfalse;
+                }
+            } else if (type == BE_MODULE) {
+                /* check if the module is named `undefined` */
+                bmodule *mod = var_toobj(vm->top);
+                if (strcmp(be_module_name(mod), "undefined") == 0) {
+                    return bfalse;     /* if the return value is module `undefined`, consider it is an error */
+                }
+            }
             return btrue;
         }
     }

lib/libesp32/berry/src/be_module.c

@@ -373,6 +373,19 @@ bbool be_module_setmember(bvm *vm, bmodule *module, bstring *attr, bvalue *src)
             vm->top += 3;   /* prevent collection results */
             be_dofunc(vm, top, 2); /* call method 'setmember' */
             vm->top -= 3;
+            int type = var_type(vm->top);
+            if (type == BE_BOOL) {
+                bbool ret = var_tobool(vm->top);
+                if (!ret) {
+                    return bfalse;
+                }
+            } else if (type == BE_MODULE) {
+                /* check if the module is named `undefined` */
+                bmodule *mod = var_toobj(vm->top);
+                if (strcmp(be_module_name(mod), "undefined") == 0) {
+                    return bfalse;     /* if the return value is module `undefined`, consider it is an error */
+                }
+            }
             return btrue;
         }
     }

lib/libesp32/berry/tests/virtual_methods2.be

@@ -1,4 +1,14 @@
 #- virtual attributes -#
+
+def assert_attribute_error(f)
+    try
+        f()
+        assert(false, 'unexpected execution flow')
+    except .. as e, m
+        assert(e == 'attribute_error')
+    end
+end
+
 class Ta
     var a, b, virtual_c
     def init()
@@ -26,3 +36,4 @@ assert(ta.c == 3)
 ta.c = 30
 assert(ta.c == 30)
 assert(ta.virtual_c == 30)
+assert_attribute_error(def() ta.d = 0 end)