[Fix] jsx-key: include duplicate-keyed jsx children in warnDuplicates option

See #2614 (comment); fixes #2614.

Author: ljharb

lib/rules/jsx-key.js

@@ -104,9 +104,11 @@ module.exports = {
       });
     }
 
+    const seen = new WeakSet();
+
     return {
-      ArrayExpression(node) {
-        const jsx = node.elements.filter((x) => x.type === 'JSXElement');
+      'ArrayExpression, JSXElement > JSXElement'(node) {
+        const jsx = (node.type === 'ArrayExpression' ? node.elements : node.parent.children).filter((x) => x.type === 'JSXElement');
         if (jsx.length === 0) {
           return;
         }
@@ -128,7 +130,7 @@ module.exports = {
 
               if (checkKeyMustBeforeSpread && isKeyAfterSpread(attrs)) {
                 report(context, messages.keyBeforeSpread, 'keyBeforeSpread', {
-                  node,
+                  node: node.type === 'ArrayExpression' ? node : node.parent,
                 });
               }
             });
@@ -138,9 +140,12 @@ module.exports = {
         if (warnOnDuplicates) {
           values(map).filter((v) => v.length > 1).forEach((v) => {
             v.forEach((n) => {
-              report(context, messages.nonUniqueKeys, 'nonUniqueKeys', {
-                node: n,
-              });
+              if (!seen.has(n)) {
+                seen.add(n);
+                report(context, messages.nonUniqueKeys, 'nonUniqueKeys', {
+                  node: n,
+                });
+              }
             });
           });
         }

tests/lib/rules/jsx-key.js

@@ -165,5 +165,20 @@ ruleTester.run('jsx-key', rule, {
         { messageId: 'nonUniqueKeys', line: 4 },
       ],
     },
+    {
+      code: `
+        const div = (
+          <div>
+            <span key="notunique"/>
+            <span key="notunique"/>
+          </div>
+        );
+      `,
+      options: [{ warnOnDuplicates: true }],
+      errors: [
+        { messageId: 'nonUniqueKeys', line: 4 },
+        { messageId: 'nonUniqueKeys', line: 5 },
+      ],
+    },
   ]),
 });