fix: less mutate-y

endojs · Jun 15, 2023 · 00c807e · 00c807e
1 parent 343d4d0
commit 00c807e
Show file tree

Hide file tree

Showing 2 changed files with 16 additions and 26 deletions.
diff --git a/packages/exo/src/exo-makers.js b/packages/exo/src/exo-makers.js
@@ -80,6 +80,7 @@ export const initEmpty = () => emptyRecord;
  * @returns {(...args: Parameters<I>) => (M & import('@endo/eventual-send').RemotableBrand<{}, M>)}
  */
 export const defineExoClass = (tag, interfaceGuard, init, methods, options) => {
+  harden(methods);
   const { finish = undefined } = options || {};
   /** @type {WeakMap<M,ClassContext<ReturnType<I>, M>>} */
   const contextMap = new WeakMap();
@@ -133,6 +134,7 @@ export const defineExoClassKit = (
   methodsKit,
   options,
 ) => {
+  harden(methodsKit);
   const { finish = undefined } = options || {};
   const contextMapKit = objectMap(methodsKit, () => new WeakMap());
   const getContextKit = objectMap(

diff --git a/packages/exo/src/exo-tools.js b/packages/exo/src/exo-tools.js
@@ -217,32 +217,19 @@ const bindMethod = (
 export const GET_INTERFACE_GUARD = Symbol.for('getInterfaceGuard');
 
 /**
- * Mutates `behaviorMethods` argument!
  *
  * @template {Record<string | symbol, CallableFunction>} T
  * @param {T} behaviorMethods
  * @param {import('@endo/patterns').InterfaceGuard} interfaceGuard
+ * @returns {T}
  */
-const addGetInterfaceGuardMethod = (behaviorMethods, interfaceGuard) => {
-  if (!hasOwnPropertyOf(behaviorMethods, GET_INTERFACE_GUARD)) {
-    // Note that we do not also update the interfaceGuard to describe this
-    // meta method. Currently, it is a symbol-named method, so we cannot
-    // anyway.
-    const getInterfaceGuardMethod = {
-      [GET_INTERFACE_GUARD]() {
-        return interfaceGuard;
-      },
-    }[GET_INTERFACE_GUARD];
-    defineProperties(behaviorMethods, {
-      [GET_INTERFACE_GUARD]: {
-        value: getInterfaceGuardMethod,
-        writable: false,
-        enumerable: false,
-        configurable: false,
-      },
-    });
-  }
-};
+const withGetInterfaceGuardMethod = (behaviorMethods, interfaceGuard) =>
+  harden({
+    [GET_INTERFACE_GUARD]() {
+      return interfaceGuard;
+    },
+    ...behaviorMethods,
+  });
 
 /**
  * @template {Record<string | symbol, CallableFunction>} T
@@ -260,14 +247,13 @@ export const defendPrototype = (
   thisfulMethods = false,
   interfaceGuard = undefined,
 ) => {
-  // local mutable copy
-  defineProperties(behaviorMethods, getOwnPropertyDescriptors(behaviorMethods));
   const prototype = {};
   if (hasOwnPropertyOf(behaviorMethods, 'constructor')) {
     // By ignoring any method named "constructor", we can use a
     // class.prototype as a behaviorMethods.
+    const { constructor: _, ...methods } = behaviorMethods;
     // @ts-expect-error TS misses that hasOwn check makes this safe
-    assert(delete behaviorMethods.constructor);
+    behaviorMethods = methods;
   }
   let methodGuards;
   if (interfaceGuard) {
@@ -292,8 +278,10 @@ export const defendPrototype = (
           Fail`methods ${q(unguarded)} not guarded by ${q(interfaceName)}`;
       }
     }
-    // mutates behaviorMethods
-    addGetInterfaceGuardMethod(behaviorMethods, interfaceGuard);
+    behaviorMethods = withGetInterfaceGuardMethod(
+      behaviorMethods,
+      interfaceGuard,
+    );
   }
 
   for (const prop of ownKeys(behaviorMethods)) {