typescript-eslint · JoshuaKGoldberg · Sep 15, 2025 · Jun 1, 2025 · Jun 1, 2025 · Jun 2, 2025
diff --git a/packages/eslint-plugin/src/rules/await-thenable.ts b/packages/eslint-plugin/src/rules/await-thenable.ts
@@ -1,10 +1,13 @@
-import type { TSESLint, TSESTree } from '@typescript-eslint/utils';
+import type { TSESLint } from '@typescript-eslint/utils';
+import type * as ts from 'typescript';
 
+import { TSESTree } from '@typescript-eslint/utils';
 import * as tsutils from 'ts-api-utils';
 
 import {
   Awaitable,
   createRule,
+  getConstrainedTypeAtLocation,
   getFixOrSuggest,
   getParserServices,
   isAwaitKeyword,
@@ -14,12 +17,14 @@ import {
   NullThrowsReasons,
 } from '../util';
 import { getForStatementHeadLoc } from '../util/getForStatementHeadLoc';
+import { isPromiseAggregatorMethod } from '../util/isPromiseAggregatorMethod';
 
 export type MessageId =
   | 'await'
   | 'awaitUsingOfNonAsyncDisposable'
   | 'convertToOrdinaryFor'
   | 'forAwaitOfNonAsyncIterable'
+  | 'invalidPromiseAggregatorInput'
   | 'removeAwait';
 
 export default createRule<[], MessageId>({
@@ -39,6 +44,8 @@ export default createRule<[], MessageId>({
       convertToOrdinaryFor: 'Convert to an ordinary `for...of` loop.',
       forAwaitOfNonAsyncIterable:
         'Unexpected `for await...of` of a value that is not async iterable.',
+      invalidPromiseAggregatorInput:
+        'Unexpected iterable of non-Promise (non-"Thenable") values passed to promise aggregator.',
       removeAwait: 'Remove unnecessary `await`.',
     },
     schema: [],
@@ -84,6 +91,53 @@ export default createRule<[], MessageId>({
         }
       },
 
+      CallExpression(node: TSESTree.CallExpression): void {
+        if (!isPromiseAggregatorMethod(context, services, node)) {
+          return;
+        }
+
+        const argument = node.arguments.at(0);
+
+        if (argument == null) {
+          return;
+        }
+
+        if (argument.type === TSESTree.AST_NODE_TYPES.ArrayExpression) {
+          for (const element of argument.elements) {
+            if (element == null) {
+              continue;
+            }
+
+            const type = getConstrainedTypeAtLocation(services, element);
+            const tsNode = services.esTreeNodeToTSNodeMap.get(element);
+
+            if (containsNonAwaitableType(type, tsNode, checker)) {
+              context.report({
+                node: element,
+                messageId: 'invalidPromiseAggregatorInput',
+              });
+            }
+          }
+
+          return;
+        }
+
+        const type = getConstrainedTypeAtLocation(services, argument);
+
+        if (
+          isInvalidPromiseAggregatorInput(
+            checker,
+            services.esTreeNodeToTSNodeMap.get(argument),
+            type,
+          )
+        ) {
+          context.report({
+            node: argument,
+            messageId: 'invalidPromiseAggregatorInput',
+          });
+        }
+      },
+
       'ForOfStatement[await=true]'(node: TSESTree.ForOfStatement): void {
         const type = services.getTypeAtLocation(node.right);
         if (isTypeAnyType(type)) {
@@ -176,3 +230,75 @@ export default createRule<[], MessageId>({
     };
   },
 });
+
+function isInvalidPromiseAggregatorInput(
+  checker: ts.TypeChecker,
+  node: ts.Node,
+  type: ts.Type,
+): boolean {
+  // non array/tuple/iterable types already show up as a type error
+  if (!isIterable(type, checker)) {
+    return false;
+  }
+
+  for (const part of tsutils.unionConstituents(type)) {
+    const valueTypes = getValueTypesOfArrayLike(part, checker);
+
+    if (valueTypes != null) {
+      for (const typeArgument of valueTypes) {
+        if (containsNonAwaitableType(typeArgument, node, checker)) {
+          return true;
+        }
+      }
+    }
+  }
+
+  return false;
+}
+
+function getValueTypesOfArrayLike(
+  type: ts.Type,
+  checker: ts.TypeChecker,
+): readonly ts.Type[] | null {
+  if (checker.isTupleType(type)) {
+    return checker.getTypeArguments(type);
+  }
+
+  if (checker.isArrayLikeType(type)) {
+    return [
+      nullThrows(
+        type.getNumberIndexType(),
+        'number index type should exist on an array-like',
+      ),
+    ];
+  }
+
+  // `Iterable<...>`
+  if (tsutils.isTypeReference(type)) {
+    return checker.getTypeArguments(type).slice(0, 1);
+  }
+
+  return null;
+}
+
+function containsNonAwaitableType(
+  type: ts.Type,
+  node: ts.Node,
+  checker: ts.TypeChecker,
+): boolean {
+  return tsutils
+    .unionConstituents(type)
+    .some(
+      typeArgumentPart =>
+        needsToBeAwaited(checker, node, typeArgumentPart) === Awaitable.Never,
+    );
+}
+
+function isIterable(type: ts.Type, checker: ts.TypeChecker): boolean {
+  return tsutils
+    .unionConstituents(type)
+    .every(
+      part =>
+        !!tsutils.getWellKnownSymbolPropertyOfType(part, 'iterator', checker),
+    );
+}
diff --git a/packages/eslint-plugin/src/util/isPromiseAggregatorMethod.ts b/packages/eslint-plugin/src/util/isPromiseAggregatorMethod.ts
@@ -0,0 +1,41 @@
+import type {
+  ParserServicesWithTypeInformation,
+  TSESTree,
+} from '@typescript-eslint/utils';
+import type { RuleContext } from '@typescript-eslint/utils/ts-eslint';
+
+import {
+  getConstrainedTypeAtLocation,
+  isPromiseConstructorLike,
+} from '@typescript-eslint/type-utils';
+import { AST_NODE_TYPES } from '@typescript-eslint/utils';
+
+import { getStaticMemberAccessValue } from './misc';
+
+const PROMISE_CONSTRUCTOR_ARRAY_METHODS = new Set<unknown>([
+  'all',
+  'allSettled',
+  'race',
+  'any',
+]);
+
+export function isPromiseAggregatorMethod(
+  context: RuleContext<string, unknown[]>,
+  services: ParserServicesWithTypeInformation,
+  node: TSESTree.CallExpression,
+): boolean {
+  if (node.callee.type !== AST_NODE_TYPES.MemberExpression) {
+    return false;
+  }
+
+  const staticAccessValue = getStaticMemberAccessValue(node.callee, context);
+
+  if (!PROMISE_CONSTRUCTOR_ARRAY_METHODS.has(staticAccessValue)) {
+    return false;
+  }
+
+  return isPromiseConstructorLike(
+    services.program,
+    getConstrainedTypeAtLocation(services, node.callee.object),
+  );
+}