feat(eslint-plugin): [no-extra-non-null-assertion] flag optional chain after a non-null assertion

packages/eslint-plugin/docs/rules/no-extra-non-null-assertion.md

@@ -15,6 +15,12 @@ function foo(bar: number | undefined) {
 }
 ```
 
+```ts
+function foo(bar?: { n: number }) {
+  return bar!?.n;
+}
+```
+
 Examples of **correct** code for this rule:
 
 ```ts
@@ -28,6 +34,12 @@ function foo(bar: number | undefined) {
 }
 ```
 
+```ts
+function foo(bar?: { n: number }) {
+  return bar?.n;
+}
+```
+
 ## How to use
 
 ```json

packages/eslint-plugin/src/rules/no-extra-non-null-assertion.ts

@@ -1,4 +1,5 @@
 import * as util from '../util';
+import { TSESTree } from '@typescript-eslint/experimental-utils';
 
 export default util.createRule({
   name: 'no-extra-non-null-assertion',
@@ -16,10 +17,15 @@ export default util.createRule({
   },
   defaultOptions: [],
   create(context) {
+    function checkExtraNonNullAssertion(
+      node: TSESTree.TSNonNullExpression,
+    ): void {
+      context.report({ messageId: 'noExtraNonNullAssertion', node });
+    }
+
     return {
-      'TSNonNullExpression > TSNonNullExpression'(node): void {
-        context.report({ messageId: 'noExtraNonNullAssertion', node });
-      },
+      'TSNonNullExpression > TSNonNullExpression': checkExtraNonNullAssertion,
+      'OptionalMemberExpression > TSNonNullExpression': checkExtraNonNullAssertion,
     };
   },
 });

packages/eslint-plugin/tests/rules/no-extra-non-null-assertion.test.ts

@@ -19,6 +19,13 @@ function foo(bar: number | undefined) {
   const bar: number = bar!;
 }      `,
     },
+    {
+      code: `
+function foo(bar?: { n: number }) {
+  return bar?.n;
+}
+      `,
+    },
   ],
   invalid: [
     {
@@ -62,5 +69,47 @@ function foo(bar: number | undefined) {
         },
       ],
     },
+    {
+      code: `
+function foo(bar?: { n: number }) {
+  return bar!?.n;
+}
+      `,
+      errors: [
+        {
+          messageId: 'noExtraNonNullAssertion',
+          endColumn: 14,
+          column: 10,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: `
+function foo(bar?: { n: number }) {
+  return bar!!!?.n;
+}
+      `,
+      errors: [
+        {
+          messageId: 'noExtraNonNullAssertion',
+          endColumn: 16,
+          column: 10,
+          line: 3,
+        },
+        {
+          messageId: 'noExtraNonNullAssertion',
+          endColumn: 15,
+          column: 10,
+          line: 3,
+        },
+        {
+          messageId: 'noExtraNonNullAssertion',
+          endColumn: 14,
+          column: 10,
+          line: 3,
+        },
+      ],
+    },
   ],
 });