typescript-eslint · JoshuaKGoldberg · Jan 9, 2024 · Dec 1, 2023 · Dec 1, 2023 · Dec 1, 2023
diff --git a/packages/eslint-plugin/docs/rules/prefer-promise-reject-errors.md b/packages/eslint-plugin/docs/rules/prefer-promise-reject-errors.md
@@ -0,0 +1,50 @@
+---
+description: 'Require using Error objects as Promise rejection reasons.'
+---
+
+> 🛑 This file is source code, not the primary documentation location! 🛑
+>
+> See **https://typescript-eslint.io/rules/prefer-promise-reject-errors** for documentation.
+
+This rule extends the base [`eslint/prefer-promise-reject-errors`](https://eslint.org/docs/rules/prefer-promise-reject-errors) rule.
+It uses type information to enforce that `Promise`s are only rejected with `Error` objects.
+
+## Examples
+
+<!--tabs-->
+
+### ❌ Incorrect
+
+```ts
+Promise.reject('error');
+
+const err = new Error();
+Promise.reject('an ' + err);
+
+new Promise((resolve, reject) => reject('error'));
+
+new Promise((resolve, reject) => {
+  const err = new Error();
+  reject('an ' + err);
+});
+```
+
+### ✅ Correct
+
+```ts
+Promise.reject(new Error());
+
+class CustomError extends Error {
+  // ...
+}
+Promise.reject(new CustomError());
+
+new Promise((resolve, reject) => reject(new Error()));
+
+new Promise((resolve, reject) => {
+  class CustomError extends Error {
+    // ...
+  }
+  return reject(new CustomError());
+});
+```
diff --git a/packages/eslint-plugin/src/configs/all.ts b/packages/eslint-plugin/src/configs/all.ts
@@ -125,6 +125,8 @@ export = {
    '@typescript-eslint/prefer-namespace-keyword': 'error',
    '@typescript-eslint/prefer-nullish-coalescing': 'error',
    '@typescript-eslint/prefer-optional-chain': 'error',
+    'prefer-promise-reject-errors': 'off',
+    '@typescript-eslint/prefer-promise-reject-errors': 'error',
    '@typescript-eslint/prefer-readonly': 'error',
    '@typescript-eslint/prefer-readonly-parameter-types': 'error',
    '@typescript-eslint/prefer-reduce-type-parameter': 'error',

diff --git a/packages/eslint-plugin/src/configs/disable-type-checked.ts b/packages/eslint-plugin/src/configs/disable-type-checked.ts
@@ -41,6 +41,7 @@ export = {
    '@typescript-eslint/prefer-includes': 'off',
    '@typescript-eslint/prefer-nullish-coalescing': 'off',
    '@typescript-eslint/prefer-optional-chain': 'off',
+    '@typescript-eslint/prefer-promise-reject-errors': 'off',
    '@typescript-eslint/prefer-readonly': 'off',
    '@typescript-eslint/prefer-readonly-parameter-types': 'off',
    '@typescript-eslint/prefer-reduce-type-parameter': 'off',

diff --git a/packages/eslint-plugin/src/configs/strict-type-checked.ts b/packages/eslint-plugin/src/configs/strict-type-checked.ts
@@ -61,6 +61,8 @@ export = {
    '@typescript-eslint/prefer-as-const': 'error',
    '@typescript-eslint/prefer-includes': 'error',
    '@typescript-eslint/prefer-literal-enum-member': 'error',
+    'prefer-promise-reject-errors': 'off',
+    '@typescript-eslint/prefer-promise-reject-errors': 'error',
    '@typescript-eslint/prefer-reduce-type-parameter': 'error',
    '@typescript-eslint/prefer-return-this-type': 'error',
    '@typescript-eslint/prefer-ts-expect-error': 'error',

diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
@@ -109,6 +109,7 @@ import preferLiteralEnumMember from './prefer-literal-enum-member';
 import preferNamespaceKeyword from './prefer-namespace-keyword';
 import preferNullishCoalescing from './prefer-nullish-coalescing';
 import preferOptionalChain from './prefer-optional-chain';
+import preferPromiseRejectErrors from './prefer-promise-reject-errors';
 import preferReadonly from './prefer-readonly';
 import preferReadonlyParameterTypes from './prefer-readonly-parameter-types';
 import preferReduceTypeParameter from './prefer-reduce-type-parameter';
@@ -248,6 +249,7 @@ export default {
  'prefer-namespace-keyword': preferNamespaceKeyword,
  'prefer-nullish-coalescing': preferNullishCoalescing,
  'prefer-optional-chain': preferOptionalChain,
+  'prefer-promise-reject-errors': preferPromiseRejectErrors,
  'prefer-readonly': preferReadonly,
  'prefer-readonly-parameter-types': preferReadonlyParameterTypes,
  'prefer-reduce-type-parameter': preferReduceTypeParameter,

diff --git a/packages/eslint-plugin/src/rules/no-throw-literal.ts b/packages/eslint-plugin/src/rules/no-throw-literal.ts
@@ -5,6 +5,7 @@ import * as ts from 'typescript';
 import {
  createRule,
  getParserServices,
+  isErrorLike,
  isTypeAnyType,
  isTypeUnknownType,
 } from '../util';
@@ -55,41 +56,6 @@ export default createRule<Options, MessageIds>({
  ],
  create(context, [options]) {
    const services = getParserServices(context);
-    const checker = services.program.getTypeChecker();
-
-    function isErrorLike(type: ts.Type): boolean {
-      if (type.isIntersection()) {
-        return type.types.some(isErrorLike);
-      }
-      if (type.isUnion()) {
-        return type.types.every(isErrorLike);
-      }
-
-      const symbol = type.getSymbol();
-      if (!symbol) {
-        return false;
-      }
-
-      if (symbol.getName() === 'Error') {
-        const declarations = symbol.getDeclarations() ?? [];
-        for (const declaration of declarations) {
-          const sourceFile = declaration.getSourceFile();
-          if (services.program.isSourceFileDefaultLibrary(sourceFile)) {
-            return true;
-          }
-        }
-      }
-
-      if (symbol.flags & (ts.SymbolFlags.Class | ts.SymbolFlags.Interface)) {
-        for (const baseType of checker.getBaseTypes(type as ts.InterfaceType)) {
-          if (isErrorLike(baseType)) {
-            return true;
-          }
-        }
-      }
-
-      return false;
-    }

    function checkThrowArgument(node: TSESTree.Node): void {
      if (
@@ -114,7 +80,7 @@ export default createRule<Options, MessageIds>({
        return;
      }

-      if (isErrorLike(type)) {
+      if (isErrorLike(services.program, type)) {
        return;
      }


diff --git a/packages/eslint-plugin/src/rules/prefer-promise-reject-errors.ts b/packages/eslint-plugin/src/rules/prefer-promise-reject-errors.ts
@@ -0,0 +1,153 @@
+import type { TSESTree } from '@typescript-eslint/utils';
+import { AST_NODE_TYPES } from '@typescript-eslint/utils';
+import { getDeclaredVariables } from '@typescript-eslint/utils/eslint-utils';
+
+import {
+  createRule,
+  getParserServices,
+  isErrorLike,
+  isFunction,
+  isIdentifier,
+  isPromiseConstructorLike,
+  isPromiseLike,
+  isReadonlyErrorLike,
+} from '../util';
+
+export type MessageIds = 'rejectAnError';
+
+export type Options = [
+  {
+    allowEmptyReject?: boolean;
+  },
+];
+
+export default createRule<Options, MessageIds>({
+  name: 'prefer-promise-reject-errors',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'Require using Error objects as Promise rejection reasons',
+      recommended: 'strict',
+      extendsBaseRule: true,
+      requiresTypeChecking: true,
+    },
+    schema: [
+      {
+        type: 'object',
+        properties: {
+          allowEmptyReject: {
+            type: 'boolean',
+          },
+        },
+        additionalProperties: false,
+      },
+    ],
+    messages: {
+      rejectAnError: 'Expected the Promise rejection reason to be an Error.',
+    },
+  },
+  defaultOptions: [
+    {
+      allowEmptyReject: false,
+    },
+  ],
+  create(context, [options]) {
+    const services = getParserServices(context);
+
+    function checkRejectCall(callExpression: TSESTree.CallExpression): void {
+      const argument = callExpression.arguments.at(0);
+      if (argument) {
+        const type = services.getTypeAtLocation(argument);
+        if (
+          isErrorLike(services.program, type) ||
+          isReadonlyErrorLike(services.program, type)
+        ) {
+          return;
+        }
+      } else if (options.allowEmptyReject) {
+        return;
+      }
+
+      context.report({
+        node: callExpression,
+        messageId: 'rejectAnError',
+      });
+    }
+
+    function skipChainExpression<T extends TSESTree.Node>(
+      node: T,
+    ): T | TSESTree.ChainElement {
+      return node.type === AST_NODE_TYPES.ChainExpression
+        ? node.expression
+        : node;
+    }
+
+    function typeAtLocationIsLikePromise(node: TSESTree.Node): boolean {
+      const type = services.getTypeAtLocation(node);
+      return (
+        isPromiseConstructorLike(services.program, type) ||
+        isPromiseLike(services.program, type)
+      );
+    }
+
+    return {
+      CallExpression(node): void {
+        const callee = skipChainExpression(node.callee);
+
+        if (callee.type !== AST_NODE_TYPES.MemberExpression) {
+          return;
+        }
+
+        const rejectMethodCalled = callee.computed
+          ? callee.property.type === AST_NODE_TYPES.Literal &&
+            callee.property.value === 'reject'
+          : callee.property.name === 'reject';
+
+        if (
+          !rejectMethodCalled ||
+          !typeAtLocationIsLikePromise(callee.object)
+        ) {
+          return;
+        }
+
+        checkRejectCall(node);
+      },
+      NewExpression(node): void {
+        const callee = skipChainExpression(node.callee);
+        if (
+          !isPromiseConstructorLike(
+            services.program,
+            services.getTypeAtLocation(callee),
+          )
+        ) {
+          return;
+        }
+
+        const executor = node.arguments.at(0);
+        if (!executor || !isFunction(executor)) {
+          return;
+        }
+        const rejectParamNode = executor.params.at(1);
+        if (!rejectParamNode || !isIdentifier(rejectParamNode)) {
+          return;
+        }
+
+        // reject param is always present in variables declared by executor
+        const rejectVariable = getDeclaredVariables(context, executor).find(
+          variable => variable.identifiers.includes(rejectParamNode),
+        )!;
+
+        rejectVariable.references.forEach(ref => {
+          if (
+            ref.identifier.parent.type !== AST_NODE_TYPES.CallExpression ||
+            ref.identifier !== ref.identifier.parent.callee
+          ) {
+            return;
+          }
+
+          checkRejectCall(ref.identifier.parent);
+        });
+      },
+    };
+  },
+});