fixup! review suggestions

packages/ses/src/shim-arraybuffer-transfer.js

@@ -22,10 +22,21 @@ export const shimArrayBufferTransfer = () => {
   }
   const clone = globalThis.structuredClone;
   if (typeof clone !== 'function') {
-    // Indeed, Node <= 16 has neither.
-    throw TypeError(
-      `Can only shim missing ArrayBuffer.prototype.transfer on a platform with "structuredClone"`,
-    );
+    // On a platform with neither `Array.prototype.transfer`
+    // nor `structuredClone`, this shim does nothing.
+    // For example, Node <= 16 has neither.
+    //
+    // Empty object because this shim has nothing for `addIntrinsics` to add.
+    return {};
+    // TODO Rather than doing nothing, should the endo ses-shim throw
+    // in this case?
+    // throw TypeError(
+    //   `Can only shim missing ArrayBuffer.prototype.transfer on a platform with "structuredClone"`,
+    // );
+    // For example, endo no longer supports Node <= 16. All browsers have
+    // `structuredClone`. XS has `Array.prototype.transfer`. Are there still
+    // any platforms without both that Endo should still support?
+    // What about Hermes?
   }
 
   /**
@@ -43,7 +54,7 @@ export const shimArrayBufferTransfer = () => {
         return clone(this, { transfer: [this] });
       }
       if (typeof newLength !== 'number') {
-        throw new TypeError(`transfer newLength if provided must be a number`);
+        throw TypeError(`transfer newLength if provided must be a number`);
       }
       if (newLength > oldLength) {
         const result = new ArrayBuffer(newLength);

packages/ses/test/shim-arraybuffer-transfer.test.js

@@ -1,3 +1,4 @@
+/* global globalThis */
 import test from 'ava';
 import '../index.js';
 
@@ -25,6 +26,15 @@ test('ArrayBuffer.p.transfer', t => {
   t.is(taX[2], 12);
   t.is(taX[3], undefined);
 
+  if (!('transfer' in ArrayBuffer.prototype)) {
+    t.false('structuredClone' in globalThis);
+    // Currently, shim-arraybuffer-transfer.shim, when run on a platform
+    // with neither `Array.prototype.transfer` nor `structuredClone` does
+    // not shim `Array.prototype.transfer`. Thus, we currently do not
+    // consider this absence to be a non-conformance to the endo ses-shim.
+    return;
+  }
+
   // because this test must run on platforms prior to
   // ArrayBuffer.prototype.detached, we test detachment by other means.