From ae2032a8ba4b3445f9d39284bbca381c7971fc98 Mon Sep 17 00:00:00 2001
From: Dominik Rowicki <yzukonta@gmail.com>
Date: Mon, 23 May 2022 17:11:22 +0200
Subject: [PATCH 1/4] feat(eslint-plugin): warn when spreading promises

---
 .../docs/rules/no-misused-promises.md         | 59 ++++++++++++++++++-
 .../src/rules/no-misused-promises.ts          | 34 ++++++++++-
 .../tests/rules/no-misused-promises.test.ts   | 55 +++++++++++++++++
 3 files changed, 143 insertions(+), 5 deletions(-)

diff --git a/packages/eslint-plugin/docs/rules/no-misused-promises.md b/packages/eslint-plugin/docs/rules/no-misused-promises.md
index b3d5dcbe0cbf..24e66dda7df4 100644
--- a/packages/eslint-plugin/docs/rules/no-misused-promises.md
+++ b/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 `checkSpreads` 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;
+    checkSpreads?: boolean;
   },
 ];
 
@@ -39,6 +40,7 @@ const defaultOptions: Options = [
   {
     checksConditionals: true,
     checksVoidReturn: true,
+    checkSpreads: true,
   },
 ];
 ```
@@ -101,6 +103,21 @@ For example, if you don't mind that passing a `() => Promise<void>` to a `() =>
 }
 ```
 
+### `"checkSpreads"`
+
+If you don't want to check object spreads, you can add this configuration:
+
+```json
+{
+  "@typescript-eslint/no-misused-promises": [
+    "error",
+    {
+      "checkSpreads": false
+    }
+  ]
+}
+```
+
 ### `checksConditionals: true`
 
 Examples of code for this rule with `checksConditionals: true`:
@@ -212,6 +229,42 @@ eventEmitter.on('some-event', () => {
 
 <!--/tabs-->
 
+### `checkSpreads: true`
+
+Examples of code for this rule with `checkSpreads: 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
diff --git a/packages/eslint-plugin/src/rules/no-misused-promises.ts b/packages/eslint-plugin/src/rules/no-misused-promises.ts
index 03b166ec49b0..8f7d84633c78 100644
--- a/packages/eslint-plugin/src/rules/no-misused-promises.ts
+++ b/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 : {}),
     };
   },
 });
diff --git a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
index 518b7c1d6b5d..2bd834ee9c24 100644
--- a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
+++ b/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',
+        },
+      ],
+    },
   ],
 });

From 3083b01f7dd90f8deeaaefccde1b40168965af59 Mon Sep 17 00:00:00 2001
From: Dominik Rowicki <yzukonta@gmail.com>
Date: Mon, 23 May 2022 17:49:16 +0200
Subject: [PATCH 2/4] feat(eslint-plugin): fix typo

---
 .../docs/rules/no-misused-promises.md              | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/packages/eslint-plugin/docs/rules/no-misused-promises.md b/packages/eslint-plugin/docs/rules/no-misused-promises.md
index 24e66dda7df4..203aefc178e1 100644
--- a/packages/eslint-plugin/docs/rules/no-misused-promises.md
+++ b/packages/eslint-plugin/docs/rules/no-misused-promises.md
@@ -14,7 +14,7 @@ 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`,
-`checksVoidReturn`, and `checkSpreads` properties indicating which types of
+`checksVoidReturn`, and `checksSpreads` properties indicating which types of
 misuse to flag. All are enabled by default.
 
 ## Options
@@ -24,7 +24,7 @@ type Options = [
   {
     checksConditionals?: boolean;
     checksVoidReturn?: boolean | ChecksVoidReturnOptions;
-    checkSpreads?: boolean;
+    checksSpreads?: boolean;
   },
 ];
 
@@ -40,7 +40,7 @@ const defaultOptions: Options = [
   {
     checksConditionals: true,
     checksVoidReturn: true,
-    checkSpreads: true,
+    checksSpreads: true,
   },
 ];
 ```
@@ -103,7 +103,7 @@ For example, if you don't mind that passing a `() => Promise<void>` to a `() =>
 }
 ```
 
-### `"checkSpreads"`
+### `"checksSpreads"`
 
 If you don't want to check object spreads, you can add this configuration:
 
@@ -112,7 +112,7 @@ If you don't want to check object spreads, you can add this configuration:
   "@typescript-eslint/no-misused-promises": [
     "error",
     {
-      "checkSpreads": false
+      "checksSpreads": false
     }
   ]
 }
@@ -229,9 +229,9 @@ eventEmitter.on('some-event', () => {
 
 <!--/tabs-->
 
-### `checkSpreads: true`
+### `checksSpreads: true`
 
-Examples of code for this rule with `checkSpreads: true`:
+Examples of code for this rule with `checksSpreads: true`:
 
 <!--tabs-->
 

From bcdbc121816068c00148465c6a1325218c7e7abf Mon Sep 17 00:00:00 2001
From: Dominik Rowicki <yzukonta@gmail.com>
Date: Tue, 24 May 2022 09:48:05 +0200
Subject: [PATCH 3/4] feat(eslint-plugin): handle logical expressions

---
 .../src/rules/no-misused-promises.ts          | 21 ++++++-----
 .../tests/rules/no-misused-promises.test.ts   | 35 +++++++++++++++++++
 2 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-misused-promises.ts b/packages/eslint-plugin/src/rules/no-misused-promises.ts
index 8f7d84633c78..cf2918206423 100644
--- a/packages/eslint-plugin/src/rules/no-misused-promises.ts
+++ b/packages/eslint-plugin/src/rules/no-misused-promises.ts
@@ -390,14 +390,7 @@ 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),
-        )
-      ) {
+      if (isSometimesThenable(checker, tsNode.expression)) {
         context.report({
           messageId: 'spread',
           node: node.argument,
@@ -413,6 +406,18 @@ export default util.createRule<Options, MessageId>({
   },
 });
 
+function isSometimesThenable(checker: ts.TypeChecker, node: ts.Node): boolean {
+  const type = checker.getTypeAtLocation(node);
+
+  for (const subType of tsutils.unionTypeParts(checker.getApparentType(type))) {
+    if (tsutils.isThenableType(checker, node, subType)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 // Variation on the thenable check which requires all forms of the type (read:
 // alternates in a union) to be thenable. Otherwise, you might be trying to
 // check if something is defined or undefined and get caught because one of the
diff --git a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
index 2bd834ee9c24..029bec906b64 100644
--- a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
@@ -326,6 +326,14 @@ console.log({
   someData: 42,
   ...(await getData()),
 });
+    `,
+    `
+declare const condition: boolean;
+
+console.log({ ...(condition && (await Promise.resolve({ key: 42 }))) });
+console.log({ ...(condition || (await Promise.resolve({ key: 42 }))) });
+console.log({ ...(condition ? {} : await Promise.resolve({ key: 42 })) });
+console.log({ ...(condition ? await Promise.resolve({ key: 42 }) : {}) });
     `,
     {
       code: `
@@ -344,6 +352,17 @@ console.log({
       `,
       options: [{ checksSpreads: false }],
     },
+    {
+      code: `
+declare const condition: boolean;
+
+console.log({ ...(condition && Promise.resolve({ key: 42 })) });
+console.log({ ...(condition || Promise.resolve({ key: 42 })) });
+console.log({ ...(condition ? {} : Promise.resolve({ key: 42 })) });
+console.log({ ...(condition ? Promise.resolve({ key: 42 }) : {}) });
+      `,
+      options: [{ checksSpreads: false }],
+    },
   ],
 
   invalid: [
@@ -925,5 +944,21 @@ console.log({
         },
       ],
     },
+    {
+      code: `
+declare const condition: boolean;
+
+console.log({ ...(condition && Promise.resolve({ key: 42 })) });
+console.log({ ...(condition || Promise.resolve({ key: 42 })) });
+console.log({ ...(condition ? {} : Promise.resolve({ key: 42 })) });
+console.log({ ...(condition ? Promise.resolve({ key: 42 }) : {}) });
+      `,
+      errors: [
+        { line: 4, messageId: 'spread' },
+        { line: 5, messageId: 'spread' },
+        { line: 6, messageId: 'spread' },
+        { line: 7, messageId: 'spread' },
+      ],
+    },
   ],
 });

From b41256c19b16412a6636e2eca183ddcc3f22ae44 Mon Sep 17 00:00:00 2001
From: Dominik Rowicki <yzukonta@gmail.com>
Date: Tue, 24 May 2022 10:16:00 +0200
Subject: [PATCH 4/4] feat(eslint-plugin): test spreading promises in arrays

---
 .../tests/rules/no-misused-promises.test.ts            | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
index 029bec906b64..24c9d4285d6e 100644
--- a/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-misused-promises.test.ts
@@ -334,6 +334,9 @@ console.log({ ...(condition && (await Promise.resolve({ key: 42 }))) });
 console.log({ ...(condition || (await Promise.resolve({ key: 42 }))) });
 console.log({ ...(condition ? {} : await Promise.resolve({ key: 42 })) });
 console.log({ ...(condition ? await Promise.resolve({ key: 42 }) : {}) });
+    `,
+    `
+console.log([...(await Promise.resolve(42))]);
     `,
     {
       code: `
@@ -363,6 +366,13 @@ console.log({ ...(condition ? Promise.resolve({ key: 42 }) : {}) });
       `,
       options: [{ checksSpreads: false }],
     },
+    {
+      code: `
+// This is invalid Typescript, but it shouldn't trigger this linter specifically
+console.log([...Promise.resolve(42)]);
+      `,
+      options: [{ checksSpreads: false }],
+    },
   ],
 
   invalid: [

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