perf(core): js errors as unions vs tuples to reduce allocs (#9947)

1 files changed, 14 insertions, 10 deletions

diff --git a/core/core.js b/core/core.js
index 7c39c1bae..f94ec8139 100644
--- a/core/core.js
+++ b/core/core.js
@@ -44,18 +44,23 @@
   }
 
   function processResponse(res) {
-    // const [ok, err] = res;
-    if (res[1] === null) {
-      return res[0];
+    if (!isErr(res)) {
+      return res;
     }
-    throw processErr(res[1]);
+    throw processErr(res);
+  }
+
+  // .$err_class_name is a special key that should only exist on errors
+  function isErr(res) {
+    return !!(res && res.$err_class_name);
   }
 
   function processErr(err) {
-    const [ErrorClass, args] = getErrorClassAndArgs(err.className);
+    const className = err.$err_class_name;
+    const [ErrorClass, args] = getErrorClassAndArgs(className);
     if (!ErrorClass) {
       return new Error(
-        `Unregistered error class: "${err.className}"\n  ${err.message}\n  Classes of errors returned from ops should be registered via Deno.core.registerErrorClass().`,
+        `Unregistered error class: "${className}"\n  ${err.message}\n  Classes of errors returned from ops should be registered via Deno.core.registerErrorClass().`,
       );
     }
     return new ErrorClass(err.message, ...args);
@@ -82,13 +87,12 @@
   }
 
   function opAsyncHandler(promiseId, res) {
-    // const [ok, err] = res;
     const promise = promiseTable.get(promiseId);
     promiseTable.delete(promiseId);
-    if (!res[1]) {
-      promise.resolve(res[0]);
+    if (!isErr(res)) {
+      promise.resolve(res);
     } else {
-      promise.reject(processErr(res[1]));
+      promise.reject(processErr(res));
     }
   }