fix(no-expression-statements): ignore Promise<void> when ignoreVoid is set (#866)

Author: RebeccaStevens

docs/rules/no-expression-statements.md

@@ -81,7 +81,8 @@ const defaults = {
 
 ### `ignoreVoid`
 
-When enabled, expression of type void are not flagged as violations. This options requires TypeScript in order to work.
+When enabled, expression of type `void` and `Promise<void>` are not flagged as violations.
+This options requires TypeScript in order to work.
 
 ### `ignoreSelfReturning`
 

src/rules/no-expression-statements.ts

@@ -5,6 +5,7 @@ import type {
 } from "@typescript-eslint/utils/json-schema";
 import type { RuleContext } from "@typescript-eslint/utils/ts-eslint";
 import { deepmerge } from "deepmerge-ts";
+import type ts from "typescript";
 
 import tsApiUtils from "#/conditional-imports/ts-api-utils";
 import typescript from "#/conditional-imports/typescript";
@@ -21,7 +22,11 @@ import {
   createRule,
   getTypeOfNode,
 } from "#/utils/rule";
-import { isCallExpression, isYieldExpression } from "#/utils/type-guards";
+import {
+  isCallExpression,
+  isPromiseType,
+  isYieldExpression,
+} from "#/utils/type-guards";
 
 /**
  * The name of this rule.
@@ -136,7 +141,16 @@ function checkExpressionStatement(
       };
     }
 
-    if (ignoreVoid && tsApiUtils?.isIntrinsicVoidType(returnType) === true) {
+    if (
+      ignoreVoid &&
+      (tsApiUtils?.isIntrinsicVoidType(returnType) === true ||
+        ("typeArguments" in returnType &&
+          isPromiseType(context, returnType) &&
+          (returnType.typeArguments as ts.Type[]).length > 0 &&
+          tsApiUtils?.isIntrinsicVoidType(
+            (returnType.typeArguments as ts.Type[])[0]!,
+          ) === true))
+    ) {
       return {
         context,
         descriptors: [],

tests/rules/no-expression-statements.test.ts

@@ -93,6 +93,14 @@ describe(name, () => {
           `,
           options: [{ ignoreVoid: true }],
         });
+
+        valid({
+          code: dedent`
+            function foo() { return Promise.resolve(); }
+            foo();
+          `,
+          options: [{ ignoreVoid: true }],
+        });
       });
 
       it("ignoreSelfReturning", () => {