From fd185937f9c81c62ab7ee192c79bc819dcf24496 Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Fri, 6 Dec 2024 02:56:50 +0900
Subject: [PATCH 1/4] fix(eslint-plugin): handle string like index type

---
 .../src/rules/no-unnecessary-condition.ts     |  7 +++-
 .../rules/no-unnecessary-condition.test.ts    | 42 +++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
index c4bed147eb88..e6eaf77190f6 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
@@ -751,8 +751,13 @@ export default createRule<Options, MessageId>({
           if (propType) {
             return isNullableType(propType);
           }
+          const indexInfo = checker.getIndexInfosOfType(type);
 
-          return !!checker.getIndexInfoOfType(type, ts.IndexKind.String);
+          return indexInfo.some(
+            info =>
+              getTypeName(checker, info.keyType) === 'string' &&
+              isNullableType(info.type),
+          );
         });
         return !isOwnNullable && isNullableType(prevType);
       }
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 7aaed5539e21..18c39d21fc46 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -982,6 +982,11 @@ isString('falafel');
       `,
       options: [{ checkTypePredicates: true }],
     },
+    `
+type A = { [name in Lowercase<string>]?: A };
+declare const a: A;
+a.a?.a?.a;
+    `,
   ],
 
   invalid: [
@@ -2766,5 +2771,42 @@ isString('fa' + 'lafel');
       '((string & { __brandA: string }) | (number & { __brandB: string })) & ("foo" | 123)',
       'alwaysTruthy',
     ),
+    {
+      code: `
+type A = {
+  [name in Lowercase<string>]?: {
+    [name in Lowercase<string>]: {
+      a: 1;
+    };
+  };
+};
+
+declare const a: A;
+
+a.a?.a?.a;
+      `,
+      errors: [
+        {
+          column: 7,
+          endColumn: 9,
+          endLine: 12,
+          line: 12,
+          messageId: 'neverOptionalChain',
+        },
+      ],
+      output: `
+type A = {
+  [name in Lowercase<string>]?: {
+    [name in Lowercase<string>]: {
+      a: 1;
+    };
+  };
+};
+
+declare const a: A;
+
+a.a?.a.a;
+      `,
+    },
   ],
 });

From 70584e1baad470f1998295862b32b5c9f693608e Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Fri, 6 Dec 2024 03:36:24 +0900
Subject: [PATCH 2/4] Update no-unnecessary-condition.test.ts

---
 .../rules/no-unnecessary-condition.test.ts    | 70 +++++++++++++++++++
 1 file changed, 70 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 18c39d21fc46..38bf78313892 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -987,6 +987,29 @@ type A = { [name in Lowercase<string>]?: A };
 declare const a: A;
 a.a?.a?.a;
     `,
+    `
+interface T {
+  [name: Lowercase<string>]: {
+    [name: Lowercase<string>]: {
+      [name: Lowercase<string>]: {
+        value: 'value';
+      };
+    };
+  };
+  [name: Uppercase<string>]: null | {
+    [name: Uppercase<string>]: null | {
+      [name: Uppercase<string>]: null | {
+        VALUE: 'VALUE';
+      };
+    };
+  };
+}
+
+declare const t: T;
+
+t.a.a.a.value;
+t.A?.A?.A?.VALUE;
+    `,
   ],
 
   invalid: [
@@ -2808,5 +2831,52 @@ declare const a: A;
 a.a?.a.a;
       `,
     },
+    {
+      code: `
+interface T {
+  [name: Lowercase<string>]: {
+    [name: Lowercase<string>]: {
+      [name: Lowercase<string>]: {
+        vale: 'value';
+      };
+    };
+  };
+  [name: Uppercase<string>]: null | {
+    [name: Uppercase<string>]: null | {
+      [name: Uppercase<string>]: null | {
+        VALUE: 'VALUE';
+      };
+    };
+  };
+}
+
+declare const t: T;
+
+t.a?.a?.a?.value;
+      `,
+      errors: [
+        {
+          column: 4,
+          endColumn: 6,
+          endLine: 21,
+          line: 21,
+          messageId: 'neverOptionalChain',
+        },
+        {
+          column: 7,
+          endColumn: 9,
+          endLine: 21,
+          line: 21,
+          messageId: 'neverOptionalChain',
+        },
+        {
+          column: 10,
+          endColumn: 12,
+          endLine: 21,
+          line: 21,
+          messageId: 'neverOptionalChain',
+        },
+      ],
+    },
   ],
 });

From cd592ac0d1111a043e0357cf3bce8b2026022b37 Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Fri, 6 Dec 2024 03:37:58 +0900
Subject: [PATCH 3/4] Update no-unnecessary-condition.test.ts

---
 .../rules/no-unnecessary-condition.test.ts    | 22 +++++++++++++++++++
 1 file changed, 22 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 38bf78313892..bf9497dbce68 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -2877,6 +2877,28 @@ t.a?.a?.a?.value;
           messageId: 'neverOptionalChain',
         },
       ],
+      output: `
+interface T {
+  [name: Lowercase<string>]: {
+    [name: Lowercase<string>]: {
+      [name: Lowercase<string>]: {
+        vale: 'value';
+      };
+    };
+  };
+  [name: Uppercase<string>]: null | {
+    [name: Uppercase<string>]: null | {
+      [name: Uppercase<string>]: null | {
+        VALUE: 'VALUE';
+      };
+    };
+  };
+}
+
+declare const t: T;
+
+t.a.a.a.value;
+      `,
     },
   ],
 });

From 4fd032f9075acf0ec648acd82dee1833045e30a0 Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Sat, 7 Dec 2024 01:17:58 +0900
Subject: [PATCH 4/4] review

---
 .../tests/rules/no-unnecessary-condition.test.ts              | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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 bf9497dbce68..8c92e36dd8b0 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -2837,7 +2837,7 @@ interface T {
   [name: Lowercase<string>]: {
     [name: Lowercase<string>]: {
       [name: Lowercase<string>]: {
-        vale: 'value';
+        value: 'value';
       };
     };
   };
@@ -2882,7 +2882,7 @@ interface T {
   [name: Lowercase<string>]: {
     [name: Lowercase<string>]: {
       [name: Lowercase<string>]: {
-        vale: 'value';
+        value: 'value';
       };
     };
   };

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