From 25636d2db736bd5182a09904a4a8a519802604af Mon Sep 17 00:00:00 2001
From: Christopher Hiller <boneskull@boneskull.com>
Date: Mon, 26 Aug 2024 14:01:14 -0700
Subject: [PATCH] feat(trampoline): add proper error handling

---
 packages/trampoline/src/trampoline.js       | 16 +++--
 packages/trampoline/test/trampoline.test.js | 77 ++++++++++++++++-----
 2 files changed, 70 insertions(+), 23 deletions(-)

diff --git a/packages/trampoline/src/trampoline.js b/packages/trampoline/src/trampoline.js
index 98a6b8ab1c..228e95312d 100644
--- a/packages/trampoline/src/trampoline.js
+++ b/packages/trampoline/src/trampoline.js
@@ -17,7 +17,11 @@ export function syncTrampoline(generatorFn, ...args) {
   const iterator = generatorFn(...args);
   let result = iterator.next();
   while (!result.done) {
-    result = iterator.next(result.value);
+    try {
+      result = iterator.next(result.value);
+    } catch (err) {
+      result = iterator.throw(err);
+    }
   }
   return result.value;
 }
@@ -36,9 +40,13 @@ export async function trampoline(generatorFn, ...args) {
   const iterator = generatorFn(...args);
   let result = iterator.next();
   while (!result.done) {
-    // eslint-disable-next-line no-await-in-loop
-    const val = await result.value;
-    result = iterator.next(val);
+    try {
+      // eslint-disable-next-line no-await-in-loop
+      const val = await result.value;
+      result = iterator.next(val);
+    } catch (err) {
+      result = iterator.throw(err);
+    }
   }
   return result.value;
 }
diff --git a/packages/trampoline/test/trampoline.test.js b/packages/trampoline/test/trampoline.test.js
index 98fe698606..6a5aa22b8a 100644
--- a/packages/trampoline/test/trampoline.test.js
+++ b/packages/trampoline/test/trampoline.test.js
@@ -33,12 +33,12 @@ function* operationsWithThunk(thunk, input = 0) {
  */
 function* operations(thunk, input = 0) {
   let result = input * 2; // First operation
-  result = yield thunk(result); // Call the hook, which can be sync or async
-  result *= 2; // Operation on the hook's result
-  // Check if the result is divisible by N, and if so, recurse
-  while (result < 1000) {
-    result *= 2;
+  try {
+    result = yield thunk(result); // Call the hook, which can be sync or async
+  } catch {
+    return result;
   }
+  result *= 2; // Operation on the hook's result
   return result;
 }
 
@@ -61,35 +61,74 @@ async function asyncThunk(x = 0) {
   return x + 10;
 }
 
-const expectedRecursionResult = 2980;
-const expectedResult = 1280;
+/**
+ * Asynchronous thunk which throws
+ * @param {number} _x
+ * @returns {Promise<number>}
+ */
+async function brokenAsyncThunk(_x = 0) {
+  throw new Error('insubordinate!');
+}
+
+// eslint-disable-next-line jsdoc/require-returns-check
+/**
+ * Synchronous thunk which throws
+ * @param {number} _x
+ * @returns {number}
+ */
+function brokenSyncThunk(_x = 0) {
+  throw new Error('churlish!');
+}
+
+/**
+ * IDK; it does what it does.
+ */
+const expectedRecursiveResult = 2980;
+/**
+ * Should be (2 * initial value + 10) * 2
+ */
+const expectedResult = 40;
+/**
+ * Should be 2 * initial value
+ */
+const expectedErrorResult = 10;
 
 test('synchronous execution - recursion', t => {
-  const syncResult = syncTrampoline(operationsWithThunk, syncThunk, 5);
-  t.is(syncResult, expectedRecursionResult);
+  const actual = syncTrampoline(operationsWithThunk, syncThunk, 5);
+  t.is(actual, expectedRecursiveResult);
 });
 
 test('asynchronous execution w/ sync thunk - recursion', async t => {
-  const asyncResult = await trampoline(operationsWithThunk, syncThunk, 5);
-  t.is(asyncResult, expectedRecursionResult);
+  const actual = await trampoline(operationsWithThunk, syncThunk, 5);
+  t.is(actual, expectedRecursiveResult);
 });
 
 test('asynchronous execution - recursion', async t => {
-  const asyncResult = await trampoline(operationsWithThunk, asyncThunk, 5);
-  t.is(asyncResult, expectedRecursionResult);
+  const actual = await trampoline(operationsWithThunk, asyncThunk, 5);
+  t.is(actual, expectedRecursiveResult);
 });
 
 test('synchronous execution', t => {
-  const syncResult = syncTrampoline(operations, syncThunk, 5);
-  t.is(syncResult, expectedResult);
+  const actual = syncTrampoline(operations, syncThunk, 5);
+  t.is(actual, expectedResult);
 });
 
 test('asynchronous execution w/ sync thunk', async t => {
-  const asyncResult = await trampoline(operations, syncThunk, 5);
-  t.is(asyncResult, expectedResult);
+  const actual = await trampoline(operations, syncThunk, 5);
+  t.is(actual, expectedResult);
 });
 
 test('asynchronous execution', async t => {
-  const asyncResult = await trampoline(operations, syncThunk, 5);
-  t.is(asyncResult, expectedResult);
+  const actual = await trampoline(operations, syncThunk, 5);
+  t.is(actual, expectedResult);
+});
+
+test('async error handling', async t => {
+  const actual = await trampoline(operations, brokenAsyncThunk, 5);
+  t.is(actual, expectedErrorResult);
+});
+
+test('sync error handling', t => {
+  const actual = syncTrampoline(operations, brokenSyncThunk, 5);
+  t.is(actual, expectedErrorResult);
 });