Update: no-unused-expression flags unused JSX

React's createElement call is side-effect free, as are most JSX pragmas.
An unused JSX element indicates a logic error in the same way any unused, side-effect free expression is.
This extension the no-unused-expression rule flags unused JSX elements unless the (new) allowJsx configuration option is set

lib/rules/no-unused-expressions.js

@@ -39,6 +39,10 @@ module.exports = {
             {
                 type: "object",
                 properties: {
+                    allowJsx: {
+                        type: "boolean",
+                        default: false
+                    },
                     allowShortCircuit: {
                         type: "boolean",
                         default: false
@@ -63,6 +67,7 @@ module.exports = {
 
     create(context) {
         const config = context.options[0] || {},
+            allowJsx = config.allowJsx || false,
             allowShortCircuit = config.allowShortCircuit || false,
             allowTernary = config.allowTernary || false,
             allowTaggedTemplates = config.allowTaggedTemplates || false;
@@ -140,6 +145,9 @@ module.exports = {
             },
             FunctionExpression: alwaysTrue,
             Identifier: alwaysTrue,
+            JSXElement() {
+                return !allowJsx;
+            },
             Literal: alwaysTrue,
             LogicalExpression(node) {
                 if (allowShortCircuit) {

tests/lib/rules/no-unused-expressions.js

@@ -82,6 +82,17 @@ ruleTester.run("no-unused-expressions", rule, {
         {
             code: "obj?.foo(\"bar\")",
             parserOptions: { ecmaVersion: 11 }
+        },
+
+        // JSX
+        {
+            code: "<div />",
+            options: [{ allowJsx: true }],
+            parserOptions: { ecmaFeatures: { jsx: true } }
+        },
+        {
+            code: "var partial = <div />",
+            parserOptions: { ecmaFeatures: { jsx: true } }
         }
     ],
     invalid: [
@@ -152,6 +163,13 @@ ruleTester.run("no-unused-expressions", rule, {
             code: "obj?.foo().bar",
             parserOptions: { ecmaVersion: 2020 },
             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
+        },
+
+        // JSX
+        {
+            code: "<div />",
+            parserOptions: { ecmaFeatures: { jsx: true } },
+            errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
         }
     ]
 });