fix(eslint-plugin): recognize native privacy (#5947)

Treat PrivateIdentifier class keys like TypeScript private members so no-new-null does not report private API types.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 8ebd5bf2-c44b-42d5-be25-e7936d4b0a14

Author: bmiddha

common/changes/@rushstack/eslint-plugin/native-private-null_2026-08-19-22-58-08.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/eslint-plugin",
+      "comment": "Fix no-new-null false positives for ECMAScript private class members.",
+      "type": "patch"
+    }
+  ]
+}

eslint/eslint-plugin/src/no-new-null.ts

@@ -9,6 +9,7 @@ type Options = [];
 
 interface IAccessible {
   accessibility?: TSESTree.Accessibility;
+  key?: TSESTree.Node;
 }
 
 const noNewNullRule: TSESLint.RuleModule<MessageIds, Options> = {
@@ -37,11 +38,15 @@ const noNewNullRule: TSESLint.RuleModule<MessageIds, Options> = {
 
   create: (context: TSESLint.RuleContext<MessageIds, Options>) => {
     /**
-     * Returns true if the accessibility is not explicitly set to private or protected, e.g. class properties, methods.
+     * Returns true unless a class member uses protected, TypeScript-private, or ECMAScript-private syntax.
      */
     function isPubliclyAccessible(node?: IAccessible): boolean {
       const accessibility: TSESTree.Accessibility | undefined = node?.accessibility;
-      return !(accessibility === 'private' || accessibility === 'protected');
+      return (
+        accessibility !== 'private' &&
+        accessibility !== 'protected' &&
+        node?.key?.type !== AST_NODE_TYPES.PrivateIdentifier
+      );
     }
 
     /**

eslint/eslint-plugin/src/test/no-new-null.test.ts

@@ -104,6 +104,17 @@ ruleTester.run('no-new-null', noNewNullRule, {
         '  }',
         '}'
       ].join('\n')
+    },
+    {
+      code: [
+        'class NativePrivateNulls {',
+        '  #field: string | null;',
+        '  #propertyFunc: (value: string | null) => void;',
+        '  #method(value: string | null): string | null { return value; }',
+        '  get #value(): string | null { return this.#field; }',
+        '  set #value(value: string | null) { this.#field = value; }',
+        '}'
+      ].join('\n')
     }
   ]
 });