fix(eslint-plugin): [no-unnecessary-condition] handle noUncheckedIndexedAccess true (typescript-eslint#10514)

* fix(eslint-plugin): [no-unnecessary-condition] handle index signature

* fix

* refactor

Author: yeonjuan

packages/eslint-plugin/src/rules/no-unnecessary-condition.ts

@@ -273,6 +273,10 @@ export default createRule<Options, MessageId>({
       compilerOptions,
       'strictNullChecks',
     );
+    const isNoUncheckedIndexedAccess = tsutils.isCompilerOptionEnabled(
+      compilerOptions,
+      'noUncheckedIndexedAccess',
+    );
 
     if (
       !isStrictNullChecks &&
@@ -787,11 +791,15 @@ export default createRule<Options, MessageId>({
           }
           const indexInfo = checker.getIndexInfosOfType(type);
 
-          return indexInfo.some(
-            info =>
-              getTypeName(checker, info.keyType) === 'string' &&
-              isNullableType(info.type),
-          );
+          return indexInfo.some(info => {
+            const isStringTypeName =
+              getTypeName(checker, info.keyType) === 'string';
+
+            return (
+              isStringTypeName &&
+              (isNoUncheckedIndexedAccess || isNullableType(info.type))
+            );
+          });
         });
         return !isOwnNullable && isNullableType(prevType);
       }

packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts

@@ -27,6 +27,12 @@ const optionsWithExactOptionalPropertyTypes = {
   tsconfigRootDir: rootPath,
 };
 
+const optionsWithNoUncheckedIndexedAccess = {
+  project: './tsconfig.noUncheckedIndexedAccess.json',
+  projectService: false,
+  tsconfigRootDir: getFixturesRootDir(),
+};
+
 const necessaryConditionTest = (condition: string): string => `
 declare const b1: ${condition};
 declare const b2: boolean;
@@ -607,11 +613,7 @@ const key = '1' as BrandedKey;
 foo?.[key]?.trim();
       `,
       languageOptions: {
-        parserOptions: {
-          project: './tsconfig.noUncheckedIndexedAccess.json',
-          projectService: false,
-          tsconfigRootDir: getFixturesRootDir(),
-        },
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
       },
     },
     {
@@ -665,11 +667,7 @@ function Foo(outer: Outer, key: Foo): number | undefined {
 }
       `,
       languageOptions: {
-        parserOptions: {
-          project: './tsconfig.noUncheckedIndexedAccess.json',
-          projectService: false,
-          tsconfigRootDir: getFixturesRootDir(),
-        },
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
       },
     },
     {
@@ -682,11 +680,51 @@ declare const key: Key;
 foo?.[key]?.trim();
       `,
       languageOptions: {
-        parserOptions: {
-          project: './tsconfig.noUncheckedIndexedAccess.json',
-          projectService: false,
-          tsconfigRootDir: getFixturesRootDir(),
-        },
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
+      },
+    },
+    {
+      code: `
+type Foo = {
+  key?: Record<string, { key: string }>;
+};
+declare const foo: Foo;
+foo.key?.someKey?.key;
+      `,
+      languageOptions: {
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
+      },
+    },
+    {
+      code: `
+type Foo = {
+  key?: {
+    [key: string]: () => void;
+  };
+};
+declare const foo: Foo;
+foo.key?.value?.();
+      `,
+      languageOptions: {
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
+      },
+    },
+    {
+      code: `
+type A = {
+  [name in Lowercase<string>]?: {
+    [name in Lowercase<string>]: {
+      a: 1;
+    };
+  };
+};
+
+declare const a: A;
+
+a.a?.a?.a;
+      `,
+      languageOptions: {
+        parserOptions: optionsWithNoUncheckedIndexedAccess,
       },
     },
     `