From cc08aab7d28f5b5573c80a3766714944bf666160 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 15 May 2023 22:22:39 -0700
Subject: [PATCH] Better error stack traces

---
 package.json             |  1 +
 src/task.ts              | 27 ++++++++++++++----------
 src/transfer_handlers.ts | 44 ++++++++++++++++++++++++++++++++++++----
 tsconfig.json            |  2 +-
 4 files changed, 58 insertions(+), 16 deletions(-)

diff --git a/package.json b/package.json
index 24e9fa4..3187764 100644
--- a/package.json
+++ b/package.json
@@ -39,6 +39,7 @@
   "devDependencies": {
     "chai": "4.2.0",
     "conditional-type-checks": "1.0.5",
+    "error-stack-parser": "^2.1.4",
     "esbuild": "^0.17.15",
     "husky": "4.2.5",
     "karma": "^6.4.1",
diff --git a/src/task.ts b/src/task.ts
index df2a6df..f23a391 100644
--- a/src/task.ts
+++ b/src/task.ts
@@ -69,46 +69,51 @@ export class SynclinkTask<T> {
     });
   }
 
-  schedule_async(): this {
+  _schedule_async(): Promise<T> {
     if (this.mode === "async") {
       // already scheduled
-      return this;
+      return this._promise;
     }
     if (this.mode === "sync") {
       throw new Error("Already synchronously scheduled");
     }
     this.mode = "async";
-    this.do_async().then(
+    const p = this.do_async().then(
       (value) => {
         // console.log("resolving", this.taskId, "value", value);
         this._resolved = true;
         this._result = value;
         this._resolve(value);
+        return value;
       },
       (reason) => {
         this._exception = reason;
         this._reject(reason);
+        throw reason;
       },
     );
+    this._promise = p;
+    return p;
+  }
+
+  schedule_async(): this {
+    this._schedule_async();
     return this;
   }
 
-  async then<S>(
+  then<S>(
     onfulfilled: (value: T) => S,
     onrejected: (reason: any) => S,
   ): Promise<S> {
-    this.schedule_async();
-    return this._promise.then(onfulfilled, onrejected);
+    return this._schedule_async().then(onfulfilled, onrejected);
   }
 
-  catch<S>(onrejected: (reason: any) => S): Promise<S> {
-    this.schedule_async();
-    return this._promise.catch(onrejected);
+  catch<S>(onrejected: (reason: any) => S): Promise<S | T> {
+    return this._schedule_async().catch(onrejected);
   }
 
   finally(onfinally: () => void): Promise<T> {
-    this.schedule_async();
-    return this._promise.finally(onfinally);
+    return this._schedule_async().finally(onfinally);
   }
 
   schedule_sync(): this {
diff --git a/src/transfer_handlers.ts b/src/transfer_handlers.ts
index daa462b..5e076e2 100644
--- a/src/transfer_handlers.ts
+++ b/src/transfer_handlers.ts
@@ -3,6 +3,7 @@ import { generateUUID } from "./request_response";
 import { createProxy, expose, wrap } from "./async_task";
 import { FakeMessageChannel } from "./fake_message_channel";
 import { ProxyMarked, proxyMarker } from "./types";
+import * as ErrorStackParser from "error-stack-parser";
 
 export const throwMarker = Symbol("Synclink.thrown");
 
@@ -103,6 +104,44 @@ type SerializedThrownValue =
   | { isError: true; value: Error }
   | { isError: false; value: unknown };
 
+const CHROME_IE_STACK_REGEXP = /^\s*at .*(\S+:\d+|\(native\))/m;
+
+function renderChromeStack(s: ErrorStackParser.StackFrame): string {
+  const locationInfo = [s.fileName, s.lineNumber, s.columnNumber].join(":");
+  if (s.functionName) {
+    return `    at ${s.functionName} (${locationInfo})`;
+  } else {
+    return `    at ${locationInfo}`;
+  }
+}
+
+function renderFirefoxStack(s: ErrorStackParser.StackFrame): string {
+  const locationInfo = [s.fileName, s.lineNumber, s.columnNumber].join(":");
+  return `${s.functionName || ""}@${locationInfo}`;
+}
+
+function fixStackTrace(origError: Error): Error {
+  const e = new Error(origError.message);
+  e.name = origError.name;
+  const isChromeStack = origError.stack?.match(CHROME_IE_STACK_REGEXP);
+  const stackList = ErrorStackParser.parse(origError)
+    .concat(ErrorStackParser.parse(e))
+    .filter(
+      (s) =>
+        !s.fileName ||
+        !/synclink\.m?js$/.test(s.fileName) ||
+        s.functionName?.startsWith("SynclinkTask.") ||
+        s.functionName?.startsWith("then"),
+    )
+    .map(isChromeStack ? renderChromeStack : renderFirefoxStack);
+  if (isChromeStack) {
+    stackList.unshift(e.stack!.split("\n", 2)[0]);
+  }
+  const stack = stackList.join("\n");
+  e.stack = stack;
+  return e;
+}
+
 /**
  * Internal transfer handler to handle thrown exceptions.
  */
@@ -130,10 +169,7 @@ export const throwTransferHandler: TransferHandler<
   },
   deserialize(serialized) {
     if (serialized.isError) {
-      throw Object.assign(
-        new Error(serialized.value.message),
-        serialized.value,
-      );
+      throw fixStackTrace(serialized.value);
     }
     throw serialized.value;
   },
diff --git a/tsconfig.json b/tsconfig.json
index a06f6a4..78ef081 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
     /* Basic Options */
-    "target": "es2015" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */,
+    "target": "ES2017" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */,
     "module": "esnext" /* Specify module code generation: 'none', commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */,
     "lib": [
       "esnext",