feat: Add valid-expect-in-promise rule

docs/rules/valid-expect-in-promise.md

@@ -0,0 +1,72 @@
+# Require promises that have expectations in their chain to be valid (`valid-expect-in-promise`)
+
+Ensure promises that include expectations are returned or awaited.
+
+## Rule details
+
+This rule flags any promises within the body of a test that include expectations
+that have either not been returned or awaited.
+
+The following patterns are considered warnings:
+
+```js
+test('promises a person', () => {
+  api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+});
+
+test('promises a counted person', () => {
+  const promise = api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+
+  promise.then(() => {
+    expect(analytics.gottenPeopleCount).toBe(1);
+  });
+});
+
+test('promises multiple people', () => {
+  const firstPromise = api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+  const secondPromise = api.getPersonByName('alice').then((person) => {
+    expect(person).toHaveProperty('name', 'Alice');
+  });
+
+  return Promise.any([firstPromise, secondPromise]);
+});
+```
+
+The following pattern is not a warning:
+
+```js
+test('promises a person', async () => {
+  await api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+});
+
+test('promises a counted person', () => {
+  let promise = api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+
+  promise = promise.then(() => {
+    expect(analytics.gottenPeopleCount).toBe(1);
+  });
+
+  return promise;
+});
+
+test('promises multiple people', () => {
+  const firstPromise = api.getPersonByName('bob').then((person) => {
+    expect(person).toHaveProperty('name', 'Bob');
+  });
+  const secondPromise = api.getPersonByName('alice').then((person) => {
+    expect(person).toHaveProperty('name', 'Alice');
+  });
+
+  return Promise.allSettled([firstPromise, secondPromise]);
+});
+```

src/index.ts

@@ -41,6 +41,7 @@ import requireHook from './rules/require-hook';
 import requireSoftAssertions from './rules/require-soft-assertions';
 import requireTopLevelDescribe from './rules/require-top-level-describe';
 import validExpect from './rules/valid-expect';
+import validExpectInPromise from './rules/valid-expect-in-promise';
 import validTitle from './rules/valid-title';
 
 const index = {
@@ -88,6 +89,7 @@ const index = {
     'require-soft-assertions': requireSoftAssertions,
     'require-top-level-describe': requireTopLevelDescribe,
     'valid-expect': validExpect,
+    'valid-expect-in-promise': validExpectInPromise,
     'valid-title': validTitle,
   },
 };
@@ -116,6 +118,7 @@ const sharedConfig = {
     'playwright/no-wait-for-timeout': 'warn',
     'playwright/prefer-web-first-assertions': 'error',
     'playwright/valid-expect': 'error',
+    'playwright/valid-expect-in-promise': 'error',
     'playwright/valid-title': 'error',
   },
 };