Merge branch 'main' into issue-4428

package.json

@@ -83,7 +83,7 @@
     "cross-env": "^7.0.3",
     "cspell": "^5.12.3",
     "cz-conventional-changelog": "^3.3.0",
-    "downlevel-dts": "^0.7.0",
+    "downlevel-dts": "^0.8.0",
     "enhanced-resolve": "^5.8.3",
     "eslint": "^8.1.0",
     "eslint-plugin-eslint-comments": "^3.2.0",

packages/eslint-plugin/src/rules/explicit-function-return-type.ts

@@ -2,7 +2,8 @@ import { AST_NODE_TYPES, TSESTree } from '@typescript-eslint/utils';
 import * as util from '../util';
 import {
   checkFunctionReturnType,
-  checkFunctionExpressionReturnType,
+  isValidFunctionExpressionReturnType,
+  ancestorHasReturnType,
 } from '../util/explicitReturnTypeUtils';
 
 type Options = [
@@ -78,7 +79,15 @@ export default util.createRule<Options, MessageIds>({
           return;
         }
 
-        checkFunctionExpressionReturnType(node, options, sourceCode, loc =>
+        if (
+          options.allowTypedFunctionExpressions &&
+          (isValidFunctionExpressionReturnType(node, options) ||
+            ancestorHasReturnType(node))
+        ) {
+          return;
+        }
+
+        checkFunctionReturnType(node, options, sourceCode, loc =>
           context.report({
             node,
             loc,
@@ -87,6 +96,10 @@ export default util.createRule<Options, MessageIds>({
         );
       },
       FunctionDeclaration(node): void {
+        if (options.allowTypedFunctionExpressions && node.returnType) {
+          return;
+        }
+
         checkFunctionReturnType(node, options, sourceCode, loc =>
           context.report({
             node,

packages/eslint-plugin/src/rules/explicit-module-boundary-types.ts

@@ -8,6 +8,7 @@ import {
   FunctionExpression,
   FunctionNode,
   isTypedFunctionExpression,
+  ancestorHasReturnType,
 } from '../util/explicitReturnTypeUtils';
 
 type Options = [
@@ -387,55 +388,6 @@ export default util.createRule<Options, MessageIds>({
       }
     }
 
-    /**
-     * Check whether any ancestor of the provided function has a valid return type.
-     * This function assumes that the function either:
-     * - belongs to an exported function chain validated by isExportedHigherOrderFunction
-     * - is directly exported itself
-     */
-    function ancestorHasReturnType(node: FunctionNode): boolean {
-      let ancestor = node.parent;
-
-      if (ancestor?.type === AST_NODE_TYPES.Property) {
-        ancestor = ancestor.value;
-      }
-
-      // if the ancestor is not a return, then this function was not returned at all, so we can exit early
-      const isReturnStatement =
-        ancestor?.type === AST_NODE_TYPES.ReturnStatement;
-      const isBodylessArrow =
-        ancestor?.type === AST_NODE_TYPES.ArrowFunctionExpression &&
-        ancestor.body.type !== AST_NODE_TYPES.BlockStatement;
-      if (!isReturnStatement && !isBodylessArrow) {
-        return false;
-      }
-
-      while (ancestor) {
-        switch (ancestor.type) {
-          case AST_NODE_TYPES.ArrowFunctionExpression:
-          case AST_NODE_TYPES.FunctionExpression:
-          case AST_NODE_TYPES.FunctionDeclaration:
-            if (ancestor.returnType) {
-              return true;
-            }
-            // assume
-            break;
-
-          // const x: Foo = () => {};
-          // Assume that a typed variable types the function expression
-          case AST_NODE_TYPES.VariableDeclarator:
-            if (ancestor.id.typeAnnotation) {
-              return true;
-            }
-            break;
-        }
-
-        ancestor = ancestor.parent;
-      }
-
-      return false;
-    }
-
     function checkEmptyBodyFunctionExpression(
       node: TSESTree.TSEmptyBodyFunctionExpression,
     ): void {

packages/eslint-plugin/src/util/explicitReturnTypeUtils.ts

@@ -293,11 +293,57 @@ function checkFunctionExpressionReturnType(
   checkFunctionReturnType(node, options, sourceCode, report);
 }
 
+/**
+ * Check whether any ancestor of the provided function has a valid return type.
+ */
+function ancestorHasReturnType(node: FunctionNode): boolean {
+  let ancestor = node.parent;
+
+  if (ancestor?.type === AST_NODE_TYPES.Property) {
+    ancestor = ancestor.value;
+  }
+
+  // if the ancestor is not a return, then this function was not returned at all, so we can exit early
+  const isReturnStatement = ancestor?.type === AST_NODE_TYPES.ReturnStatement;
+  const isBodylessArrow =
+    ancestor?.type === AST_NODE_TYPES.ArrowFunctionExpression &&
+    ancestor.body.type !== AST_NODE_TYPES.BlockStatement;
+  if (!isReturnStatement && !isBodylessArrow) {
+    return false;
+  }
+
+  while (ancestor) {
+    switch (ancestor.type) {
+      case AST_NODE_TYPES.ArrowFunctionExpression:
+      case AST_NODE_TYPES.FunctionExpression:
+      case AST_NODE_TYPES.FunctionDeclaration:
+        if (ancestor.returnType) {
+          return true;
+        }
+        break;
+
+      // const x: Foo = () => {};
+      // Assume that a typed variable types the function expression
+      case AST_NODE_TYPES.VariableDeclarator:
+        if (ancestor.id.typeAnnotation) {
+          return true;
+        }
+        break;
+    }
+
+    ancestor = ancestor.parent;
+  }
+
+  return false;
+}
+
 export {
   checkFunctionExpressionReturnType,
   checkFunctionReturnType,
   doesImmediatelyReturnFunctionExpression,
   FunctionExpression,
   FunctionNode,
   isTypedFunctionExpression,
+  isValidFunctionExpressionReturnType,
+  ancestorHasReturnType,
 };

packages/eslint-plugin/tests/rules/explicit-function-return-type.test.ts

@@ -400,6 +400,68 @@ new Foo(1, () => {});
       code: 'const log = (message: string) => void console.log(message);',
       options: [{ allowConciseArrowFunctionExpressionsStartingWithVoid: true }],
     },
+    {
+      filename: 'test.ts',
+      code: `
+type HigherOrderType = () => (arg1: string) => (arg2: number) => string;
+const x: HigherOrderType = () => arg1 => arg2 => 'foo';
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: true,
+          allowHigherOrderFunctions: true,
+        },
+      ],
+    },
+    {
+      filename: 'test.ts',
+      code: `
+type HigherOrderType = () => (arg1: string) => (arg2: number) => string;
+const x: HigherOrderType = () => arg1 => arg2 => 'foo';
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: true,
+          allowHigherOrderFunctions: false,
+        },
+      ],
+    },
+    {
+      filename: 'test.ts',
+      code: `
+interface Foo {
+  foo: string;
+  arrowFn: () => string;
+}
+
+function foo(): Foo {
+  return {
+    foo: 'foo',
+    arrowFn: () => 'test',
+  };
+}
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: true,
+          allowHigherOrderFunctions: true,
+        },
+      ],
+    },
+    {
+      filename: 'test.ts',
+      code: `
+type Foo = (arg1: string) => string;
+type Bar<T> = (arg2: string) => T;
+const x: Bar<Foo> = arg1 => arg2 => arg1 + arg2;
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: true,
+          allowHigherOrderFunctions: true,
+        },
+      ],
+    },
   ],
   invalid: [
     {
@@ -1027,6 +1089,64 @@ foo({
     {
       filename: 'test.ts',
       code: `
+type HigherOrderType = () => (arg1: string) => (arg2: number) => string;
+const x: HigherOrderType = () => arg1 => arg2 => 'foo';
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: false,
+          allowHigherOrderFunctions: true,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'missingReturnType',
+          line: 3,
+          endLine: 3,
+          column: 42,
+          endColumn: 49,
+        },
+      ],
+    },
+    {
+      filename: 'test.ts',
+      code: `
+type HigherOrderType = () => (arg1: string) => (arg2: number) => string;
+const x: HigherOrderType = () => arg1 => arg2 => 'foo';
+      `,
+      options: [
+        {
+          allowTypedFunctionExpressions: false,
+          allowHigherOrderFunctions: false,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'missingReturnType',
+          line: 3,
+          endLine: 3,
+          column: 28,
+          endColumn: 33,
+        },
+        {
+          messageId: 'missingReturnType',
+          line: 3,
+          endLine: 3,
+          column: 34,
+          endColumn: 41,
+        },
+        {
+          messageId: 'missingReturnType',
+          line: 3,
+          endLine: 3,
+          column: 42,
+          endColumn: 49,
+        },
+      ],
+    },
+    {
+      filename: 'test.ts',
+      code: `
 const func = (value: number) => ({ type: 'X', value } as any);
 const func = (value: number) => ({ type: 'X', value } as Action);
       `,

packages/type-utils/tests/isTypeReadonly.test.ts

@@ -1,5 +1,5 @@
 import * as ts from 'typescript';
-import { TSESTree } from '@typescript-eslint/experimental-utils';
+import { TSESTree } from '@typescript-eslint/utils';
 import { parseForESLint } from '@typescript-eslint/parser';
 import {
   isTypeReadonly,

yarn.lock

@@ -4006,9 +4006,9 @@
   integrity sha512-kUNnecmtkunAoQ3CnjmMkzNU/gtxG8guhi+Fk2U/kOpIKjIMKnXGp4IJCgQJrXSgMsWYimYG4TGjz/UzbGEBTw==
 
 "@types/prettier@*", "@types/prettier@^2.1.5", "@types/prettier@^2.4.2":
-  version "2.4.2"
-  resolved "https://registry.yarnpkg.com/@types/prettier/-/prettier-2.4.2.tgz#4c62fae93eb479660c3bd93f9d24d561597a8281"
-  integrity sha512-ekoj4qOQYp7CvjX8ZDBgN86w3MqQhLE1hczEJbEIjgFEumDy+na/4AJAbLXfgEWFNB2pKadM5rPFtuSGMWK7xA==
+  version "2.4.3"
+  resolved "https://registry.yarnpkg.com/@types/prettier/-/prettier-2.4.3.tgz#a3c65525b91fca7da00ab1a3ac2b5a2a4afbffbf"
+  integrity sha512-QzSuZMBuG5u8HqYz01qtMdg/Jfctlnvj1z/lYnIDXs/golxw0fxtRAHd9KrzjR7Yxz1qVeI00o0kiO3PmVdJ9w==
 
 "@types/prop-types@*":
   version "15.7.4"
@@ -6588,10 +6588,10 @@ dotenv@~10.0.0:
   resolved "https://registry.yarnpkg.com/dotenv/-/dotenv-10.0.0.tgz#3d4227b8fb95f81096cdd2b66653fb2c7085ba81"
   integrity sha512-rlBi9d8jpv9Sf1klPjNfFAuWDjKLwTIJJ/VxtoTwIR6hnZxcEOQCZg2oIL3MWBYw5GpUDKOEnND7LXTbIpQ03Q==
 
-downlevel-dts@^0.7.0:
-  version "0.7.0"
-  resolved "https://registry.yarnpkg.com/downlevel-dts/-/downlevel-dts-0.7.0.tgz#155c24310dad8a4820ad077e64b15a8c461aa932"
-  integrity sha512-tcjGqElN0/oad/LJBlaxmZ3zOYEQOBbGuirKzif8s1jeRiWBdNX9H6OBFlRjOQkosXgV+qSjs4osuGCivyZ4Jw==
+downlevel-dts@^0.8.0:
+  version "0.8.0"
+  resolved "https://registry.yarnpkg.com/downlevel-dts/-/downlevel-dts-0.8.0.tgz#bed86768357824b1a04f60df79d8b0867b83a382"
+  integrity sha512-wBy+Q0Ya/1XRz9MMaj3BXH95E8aSckY3lppmUnf8Qv7dUg0wbWm3szDiVL4PdAvwcS7JbBBDPhCXeAGNT3ttFQ==
   dependencies:
     semver "^7.3.2"
     shelljs "^0.8.3"
@@ -6967,9 +6967,9 @@ eslint-visitor-keys@^2.0.0:
   integrity sha512-0rSmRBzXgDzIsD6mGdJgevzgezI534Cer5L/vyMX0kHzT/jiB43jRhd9YUlMGYLQy2zprNmoT8qasCGtY+QaKw==
 
 eslint-visitor-keys@^3.0.0:
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/eslint-visitor-keys/-/eslint-visitor-keys-3.1.0.tgz#eee4acea891814cda67a7d8812d9647dd0179af2"
-  integrity sha512-yWJFpu4DtjsWKkt5GeNBBuZMlNcYVs6vRCLoCVEJrTjaSB6LC98gFipNK/erM2Heg/E8mIK+hXG/pJMLK+eRZA==
+  version "3.2.0"
+  resolved "https://registry.yarnpkg.com/eslint-visitor-keys/-/eslint-visitor-keys-3.2.0.tgz#6fbb166a6798ee5991358bc2daa1ba76cc1254a1"
+  integrity sha512-IOzT0X126zn7ALX0dwFiUQEdsfzrm4+ISsQS8nukaJXwEyYKRSnEIIDULYg1mCtGp7UUXgfGl7BIolXREQK+XQ==
 
 eslint@*, eslint@^8.1.0:
   version "8.1.0"
@@ -13136,9 +13136,9 @@ rimraf@^2.6.3:
     glob "^7.1.3"
 
 rollup@^2.59.0:
-  version "2.63.0"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.63.0.tgz#fe2f7fec2133f3fab9e022b9ac245628d817c6bb"
-  integrity sha512-nps0idjmD+NXl6OREfyYXMn/dar3WGcyKn+KBzPdaLecub3x/LrId0wUcthcr8oZUAcZAR8NKcfGGFlNgGL1kQ==
+  version "2.64.0"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.64.0.tgz#f0f59774e21fbb56de438a37d06a2189632b207a"
+  integrity sha512-+c+lbw1lexBKSMb1yxGDVfJ+vchJH3qLbmavR+awDinTDA2C5Ug9u7lkOzj62SCu0PKUExsW36tpgW7Fmpn3yQ==
   optionalDependencies:
     fsevents "~2.3.2"