feat(eslint-plugin): [no-misused-promises] warn when spreading promises

packages/eslint-plugin/docs/rules/no-misused-promises.md

@@ -13,9 +13,9 @@ See [`no-floating-promises`](./no-floating-promises.md) for detecting unhandled
 
 ## Rule Details
 
-This rule accepts a single option which is an object with `checksConditionals`
-and `checksVoidReturn` properties indicating which types of misuse to flag.
-Both are enabled by default.
+This rule accepts a single option which is an object with `checksConditionals`,
+`checksVoidReturn`, and `checksSpreads` properties indicating which types of
+misuse to flag. All are enabled by default.
 
 ## Options
 
@@ -24,6 +24,7 @@ type Options = [
   {
     checksConditionals?: boolean;
     checksVoidReturn?: boolean | ChecksVoidReturnOptions;
+    checksSpreads?: boolean;
   },
 ];
 
@@ -39,6 +40,7 @@ const defaultOptions: Options = [
   {
     checksConditionals: true,
     checksVoidReturn: true,
+    checksSpreads: true,
   },
 ];
 ```
@@ -101,6 +103,21 @@ For example, if you don't mind that passing a `() => Promise<void>` to a `() =>
 }
 ```
 
+### `"checksSpreads"`
+
+If you don't want to check object spreads, you can add this configuration:
+
+```json
+{
+  "@typescript-eslint/no-misused-promises": [
+    "error",
+    {
+      "checksSpreads": false
+    }
+  ]
+}
+```
+
 ### `checksConditionals: true`
 
 Examples of code for this rule with `checksConditionals: true`:
@@ -212,6 +229,42 @@ eventEmitter.on('some-event', () => {
 
 <!--/tabs-->
 
+### `checksSpreads: true`
+
+Examples of code for this rule with `checksSpreads: true`:
+
+<!--tabs-->
+
+#### ❌ Incorrect
+
+```ts
+const getData = () => someAsyncOperation({ myArg: 'foo' });
+
+return { foo: 42, ...getData() };
+
+const getData2 = async () => {
+  await someAsyncOperation({ myArg: 'foo' });
+};
+
+return { foo: 42, ...getData2() };
+```
+
+#### ✅ Correct
+
+```ts
+const getData = () => someAsyncOperation({ myArg: 'foo' });
+
+return { foo: 42, ...(await getData()) };
+
+const getData2 = async () => {
+  await someAsyncOperation({ myArg: 'foo' });
+};
+
+return { foo: 42, ...(await getData2()) };
+```
+
+<!--tabs-->
+
 ## When Not To Use It
 
 If you do not use Promises in your codebase or are not concerned with possible

packages/eslint-plugin/src/rules/no-misused-promises.ts

@@ -8,6 +8,7 @@ type Options = [
   {
     checksConditionals?: boolean;
     checksVoidReturn?: boolean | ChecksVoidReturnOptions;
+    checksSpreads?: boolean;
   },
 ];
 
@@ -25,7 +26,8 @@ type MessageId =
   | 'voidReturnVariable'
   | 'voidReturnProperty'
   | 'voidReturnReturnValue'
-  | 'voidReturnAttribute';
+  | 'voidReturnAttribute'
+  | 'spread';
 
 function parseChecksVoidReturn(
   checksVoidReturn: boolean | ChecksVoidReturnOptions | undefined,
@@ -75,6 +77,7 @@ export default util.createRule<Options, MessageId>({
       voidReturnAttribute:
         'Promise-returning function provided to attribute where a void return was expected.',
       conditional: 'Expected non-Promise value in a boolean conditional.',
+      spread: 'Expected a non-Promise value to be spreaded in an object.',
     },
     schema: [
       {
@@ -99,6 +102,9 @@ export default util.createRule<Options, MessageId>({
               },
             ],
           },
+          checksSpreads: {
+            type: 'boolean',
+          },
         },
       },
     ],
@@ -108,10 +114,11 @@ export default util.createRule<Options, MessageId>({
     {
       checksConditionals: true,
       checksVoidReturn: true,
+      checksSpreads: true,
     },
   ],
 
-  create(context, [{ checksConditionals, checksVoidReturn }]) {
+  create(context, [{ checksConditionals, checksVoidReturn, checksSpreads }]) {
     const parserServices = util.getParserServices(context);
     const checker = parserServices.program.getTypeChecker();
 
@@ -153,6 +160,10 @@ export default util.createRule<Options, MessageId>({
         }
       : {};
 
+    const spreadChecks: TSESLint.RuleListener = {
+      SpreadElement: checkSpread,
+    };
+
     function checkTestConditional(node: {
       test: TSESTree.Expression | null;
     }): void {
@@ -376,9 +387,28 @@ export default util.createRule<Options, MessageId>({
       }
     }
 
+    function checkSpread(node: TSESTree.SpreadElement): void {
+      const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
+
+      if (
+        node.argument.type === AST_NODE_TYPES.CallExpression &&
+        tsutils.isThenableType(
+          checker,
+          tsNode.expression,
+          checker.getTypeAtLocation(tsNode.expression),
+        )
+      ) {
+        context.report({
+          messageId: 'spread',
+          node: node.argument,
+        });
+      }
+    }
+
     return {
       ...(checksConditionals ? conditionalChecks : {}),
       ...(checksVoidReturn ? voidReturnChecks : {}),
+      ...(checksSpreads ? spreadChecks : {}),
     };
   },
 });

packages/eslint-plugin/tests/rules/no-misused-promises.test.ts

@@ -316,6 +316,34 @@ const _ = <Component onEvent={async () => {}} />;
       `,
       filename: 'react.tsx',
     },
+    `
+console.log({ ...(await Promise.resolve({ key: 42 })) });
+    `,
+    `
+const getData = Promise.resolve({ key: 42 });
+
+console.log({
+  someData: 42,
+  ...(await getData()),
+});
+    `,
+    {
+      code: `
+console.log({ ...Promise.resolve({ key: 42 }) });
+      `,
+      options: [{ checksSpreads: false }],
+    },
+    {
+      code: `
+const getData = Promise.resolve({ key: 42 });
+
+console.log({
+  someData: 42,
+  ...getData(),
+});
+      `,
+      options: [{ checksSpreads: false }],
+    },
   ],
 
   invalid: [
@@ -870,5 +898,32 @@ it('', async () => {});
         },
       ],
     },
+    {
+      code: `
+console.log({ ...Promise.resolve({ key: 42 }) });
+      `,
+      errors: [
+        {
+          line: 2,
+          messageId: 'spread',
+        },
+      ],
+    },
+    {
+      code: `
+const getData = () => Promise.resolve({ key: 42 });
+
+console.log({
+  someData: 42,
+  ...getData(),
+});
+      `,
+      errors: [
+        {
+          line: 6,
+          messageId: 'spread',
+        },
+      ],
+    },
   ],
 });