From bb46ef0817fe03ef71f8e0f3df0cf96bc355e068 Mon Sep 17 00:00:00 2001
From: kazizi <50566849+kazizi55@users.noreply.github.com>
Date: Sun, 2 Oct 2022 13:28:37 +0900
Subject: [PATCH] feat(eslint-plugin): allow using void as a default type for a
 generic argument if allowInGenericTypeArguments is specified (#5671)

* feat: allow using void as a default type for a generic argument

* test: allow using void as a default type for a generic argument

* fix: build error

* fix: replace any

* test: remove duplicate error

* fix: report invalidVoidNotReturnOrGeneric only one time

* Update packages/eslint-plugin/src/rules/no-invalid-void-type.ts

Co-authored-by: Josh Goldberg <git@joshuakgoldberg.com>

* Update packages/eslint-plugin/src/rules/no-invalid-void-type.ts

Co-authored-by: Josh Goldberg <git@joshuakgoldberg.com>

* fix: rename function name

* refactor: delete isTSTypeParameter and inline

* refactor: checkDefaultVoid

Co-authored-by: Josh Goldberg <git@joshuakgoldberg.com>
---
 .../src/rules/no-invalid-void-type.ts         | 25 ++++++++++
 .../tests/rules/no-invalid-void-type.test.ts  | 47 +------------------
 2 files changed, 27 insertions(+), 45 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-invalid-void-type.ts b/packages/eslint-plugin/src/rules/no-invalid-void-type.ts
index 6b9960e9d16..7cda184e4fd 100644
--- a/packages/eslint-plugin/src/rules/no-invalid-void-type.ts
+++ b/packages/eslint-plugin/src/rules/no-invalid-void-type.ts
@@ -127,6 +127,21 @@ export default util.createRule<[Options], MessageIds>({
       }
     }
 
+    /**
+     * @brief checks if the generic type parameter defaults to void
+     */
+    function checkDefaultVoid(
+      node: TSESTree.TSVoidKeyword,
+      parentNode: TSESTree.TSTypeParameter,
+    ): void {
+      if (parentNode.default !== node) {
+        context.report({
+          messageId: 'invalidVoidNotReturnOrGeneric',
+          node,
+        });
+      }
+    }
+
     /**
      * @brief checks that a union containing void is valid
      * @return true if every member of the union is specified as a valid type in
@@ -162,6 +177,16 @@ export default util.createRule<[Options], MessageIds>({
           return;
         }
 
+        // allow <T = void> if allowInGenericTypeArguments is specified, and report if the generic type parameter extends void
+        if (
+          allowInGenericTypeArguments &&
+          node.parent.type === AST_NODE_TYPES.TSTypeParameter &&
+          node.parent.default?.type === AST_NODE_TYPES.TSVoidKeyword
+        ) {
+          checkDefaultVoid(node, node.parent);
+          return;
+        }
+
         // union w/ void must contain types from validUnionMembers, or a valid generic void type
         if (
           node.parent.type === AST_NODE_TYPES.TSUnionType &&
diff --git a/packages/eslint-plugin/tests/rules/no-invalid-void-type.test.ts b/packages/eslint-plugin/tests/rules/no-invalid-void-type.test.ts
index 0141da093b5..8164e85b2bd 100644
--- a/packages/eslint-plugin/tests/rules/no-invalid-void-type.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-invalid-void-type.test.ts
@@ -119,6 +119,8 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
     'type Generic<T> = [T];',
     'type voidPromiseUnion = void | Promise<void>;',
     'type promiseNeverUnion = Promise<void> | never;',
+    'const arrowGeneric1 = <T = void>(arg: T) => {};',
+    'declare function functionDeclaration1<T = void>(arg: T): void;',
   ],
   invalid: [
     {
@@ -141,16 +143,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
         },
       ],
     },
-    {
-      code: 'const arrowGeneric1 = <T = void>(arg: T) => {};',
-      errors: [
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 28,
-        },
-      ],
-    },
     {
       code: 'const arrowGeneric2 = <T extends void = void>(arg: T) => {};',
       errors: [
@@ -159,11 +151,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
           line: 1,
           column: 34,
         },
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 41,
-        },
       ],
     },
     {
@@ -176,16 +163,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
         },
       ],
     },
-    {
-      code: 'function functionGeneric1<T = void>(arg: T) {}',
-      errors: [
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 31,
-        },
-      ],
-    },
     {
       code: 'function functionGeneric2<T extends void = void>(arg: T) {}',
       errors: [
@@ -194,11 +171,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
           line: 1,
           column: 37,
         },
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 44,
-        },
       ],
     },
     {
@@ -211,16 +183,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
         },
       ],
     },
-    {
-      code: 'declare function functionDeclaration1<T = void>(arg: T): void;',
-      errors: [
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 43,
-        },
-      ],
-    },
     {
       code: 'declare function functionDeclaration2<T extends void = void>(arg: T): void;',
       errors: [
@@ -229,11 +191,6 @@ ruleTester.run('allowInGenericTypeArguments: true', rule, {
           line: 1,
           column: 49,
         },
-        {
-          messageId: 'invalidVoidNotReturnOrGeneric',
-          line: 1,
-          column: 56,
-        },
       ],
     },
     {