From 64cb69e1e24d09fa23376b4b5335a2d55eb2fb55 Mon Sep 17 00:00:00 2001
From: dora <31735614+dora1998@users.noreply.github.com>
Date: Sat, 15 Apr 2023 17:24:50 +0900
Subject: [PATCH 1/2] fix(eslint-plugin): [no-unnecessary-condition] allow
 nullish coalescing for naked type parameter

---
 .../src/rules/no-unnecessary-condition.ts              | 10 ++++++++--
 .../tests/rules/no-unnecessary-condition.test.ts       |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
index 6af9bc0e9e0..1d0ae09a49b 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
@@ -263,8 +263,14 @@ export default createRule<Options, MessageId>({
 
     function checkNodeForNullish(node: TSESTree.Expression): void {
       const type = getNodeType(node);
-      // Conditional is always necessary if it involves `any` or `unknown`
-      if (isTypeAnyType(type) || isTypeUnknownType(type)) {
+
+      // Conditional is always necessary if it involves `any`, `unknown` or a naked type parameter
+      if (
+        isTypeFlagSet(
+          type,
+          ts.TypeFlags.Any | ts.TypeFlags.Unknown | ts.TypeFlags.TypeParameter,
+        )
+      ) {
         return;
       }
 
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
index e3647102305..5418fa198a1 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -280,6 +280,11 @@ function test(a: string | null | undefined) {
     `
 function test(a: unknown) {
   return a ?? 'default';
+}
+    `,
+    `
+function test<T>(a: T) {
+  return a ?? 'default';
 }
     `,
     // Indexing cases

From a1c766c4d1d3fa76100de1c4aab3865adb59a30a Mon Sep 17 00:00:00 2001
From: dora <31735614+dora1998@users.noreply.github.com>
Date: Mon, 17 Apr 2023 15:11:57 +0900
Subject: [PATCH 2/2] add tests

---
 .../rules/no-unnecessary-condition.test.ts    | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
index 5418fa198a1..4cb0e1604b7 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -285,6 +285,11 @@ function test(a: unknown) {
     `
 function test<T>(a: T) {
   return a ?? 'default';
+}
+    `,
+    `
+function test<T extends string | null>(a: T) {
+  return a ?? 'default';
 }
     `,
     // Indexing cases
@@ -832,6 +837,14 @@ function test(a: string) {
       code: `
 function test(a: string | false) {
   return a ?? 'default';
+}
+      `,
+      errors: [ruleError(3, 10, 'neverNullish')],
+    },
+    {
+      code: `
+function test<T extends string>(a: T) {
+  return a ?? 'default';
 }
       `,
       errors: [ruleError(3, 10, 'neverNullish')],
@@ -863,6 +876,14 @@ function test(a: null[]) {
     },
     {
       code: `
+function test<T extends null>(a: T) {
+  return a ?? 'default';
+}
+      `,
+      errors: [ruleError(3, 10, 'alwaysNullish')],
+    },
+    {
+      code: `
 function test(a: never) {
   return a ?? 'default';
 }