[New] Add jsx-embed-condition rule

Fixes #1979

Author: Anees Iqbal

README.md

@@ -162,6 +162,7 @@ Enable the rules that you would like to use.
 * [react/jsx-curly-brace-presence](docs/rules/jsx-curly-brace-presence.md): Disallow unnecessary JSX expressions when literals alone are sufficient or enfore JSX expressions on literals in JSX children or attributes (fixable)
 * [react/jsx-curly-newline](docs/rules/jsx-curly-newline.md): Enforce consistent line breaks inside jsx curly (fixable)
 * [react/jsx-curly-spacing](docs/rules/jsx-curly-spacing.md): Enforce or disallow spaces inside of curly braces in JSX attributes (fixable)
+* [react/jsx-embed-condition](docs/rules/jsx-embed-condition.md): Disallows use of `&&` inside JSX Embeds to avoid conditional numbers from being rendered
 * [react/jsx-equals-spacing](docs/rules/jsx-equals-spacing.md): Disallow or enforce spaces around equal signs in JSX attributes (fixable)
 * [react/jsx-filename-extension](docs/rules/jsx-filename-extension.md): Restrict file extensions that may contain JSX
 * [react/jsx-first-prop-new-line](docs/rules/jsx-first-prop-new-line.md): Ensure proper position of the first property in JSX (fixable)

docs/rules/jsx-embed-condition.md

@@ -0,0 +1,34 @@
+# Disallow && condition inside JSX Embed. (react/jsx-embed-condition)
+
+This rule disallows use of `&&` inside JSX Embeds to avoid conditional numbers from being rendered.
+
+## Why?
+
+The Official React docs warns against using `&&` in inline JSX embed expressions. The reason behind this is explained well in the [Official React docs](https://reactjs.org/docs/conditional-rendering.html#inline-if-with-logical--operator).
+Imagine having a var `x` with a possible value of `1` or `0`. If you write `{x && <div />}`, it'll render `<div />` when `x` is `1` but instead of rendering
+nothing when `x` is `0`, it'll render `0` literal. This can lead to hard to figure out bugs, especially in React Native.
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```jsx
+<div>
+  {x && <MyProfile />}
+</div>
+<div>
+  {x || y && <strong>Hello</strong>}
+</div>
+```
+
+Examples of **correct** code for this rule:
+
+```jsx
+<div>
+  {x ? <MyProfile /> : null}
+</div>
+// --
+<div>
+  {x || y ? <strong>Hello</strong> : null}
+</div>
+```

index.js

@@ -22,6 +22,7 @@ const allRules = {
   'jsx-closing-tag-location': require('./lib/rules/jsx-closing-tag-location'),
   'jsx-curly-spacing': require('./lib/rules/jsx-curly-spacing'),
   'jsx-curly-newline': require('./lib/rules/jsx-curly-newline'),
+  'jsx-embed-condition': require('./lib/rules/jsx-embed-condition'),
   'jsx-equals-spacing': require('./lib/rules/jsx-equals-spacing'),
   'jsx-filename-extension': require('./lib/rules/jsx-filename-extension'),
   'jsx-first-prop-new-line': require('./lib/rules/jsx-first-prop-new-line'),

lib/rules/jsx-embed-condition.js

@@ -0,0 +1,45 @@
+/**
+ * @fileoverview Prevents usage of && condition in JSX Embeds.
+ * @author Anees Iqbal <[email protected]>
+ */
+
+'use strict';
+
+const docsUrl = require('../util/docsUrl');
+
+// -----------------------------------------------------------------------------
+// Rule Definition
+// -----------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Prevents usage of && condition in JSX embed',
+      category: 'Best Practices',
+      recommended: false,
+      url: docsUrl('jsx-embed-condition')
+    },
+
+    schema: []
+  },
+
+  create(context) {
+    return {
+      JSXExpressionContainer(node) {
+        if (
+          node.parent == null
+          || node.parent.type !== 'JSXElement'
+          || node.expression == null
+          || node.expression.type !== 'LogicalExpression'
+          || node.expression.operator === '??'
+        ) {
+          return;
+        }
+        context.report({
+          node,
+          message: 'Using && to condition JSX embeds is forbidden. Convert it to a ternary operation instead'
+        });
+      }
+    };
+  }
+};

tests/lib/rules/jsx-embed-condition.js

@@ -0,0 +1,70 @@
+/**
+ * @fileoverview Prevents usage of && condition in JSX Embeds.
+ * @author Anees Iqbal <[email protected]>
+ */
+
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const RuleTester = require('eslint').RuleTester;
+const rule = require('../../../lib/rules/jsx-embed-condition');
+const parsers = require('../../helpers/parsers');
+
+const parserOptions = {
+  ecmaVersion: 2018,
+  sourceType: 'module',
+  ecmaFeatures: {
+    jsx: true
+  }
+};
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({parserOptions});
+ruleTester.run('jsx-embed-condition', rule, {
+  valid: [].concat({
+    code: '<App>Test</App>'
+  }, {
+    code: '<App test>Another</App>'
+  }, {
+    code: '<App foo={e => bar(e)}>Hello World</App>'
+  }, {
+    code: '<App>{x ? <div></div> : null}</App>'
+  }, {
+    code: '<App>{x ? <div>Hello</div> : null}</App>'
+  }, {
+    code: '<App>{x ? <div>{y ? <y /> : <z />}</div> : null}</App>'
+  }, {
+    code: '<App x={x && y}>{x ? <div>{y ? <y /> : <z />}</div> : null}</App>'
+  }, parsers.TS({
+    code: '<App test>{x ?? <div />}</App>',
+    parserOptions: {
+      ecmaVersion: 2020
+    }
+  }, {
+    code: '<App test>{x ?? <div />}</App>',
+    parser: parsers.TYPESCRIPT_ESLINT
+  }, {
+    code: '<App test>{x ?? <div />}</App>',
+    parser: parsers['@TYPEDCRIPT_ESLINT']
+  })),
+
+  invalid: [{
+    code: '<div>{x && <div />}</div>',
+    output: '<div>{x && <div />}</div>',
+    errors: [
+      {message: 'Using && to condition JSX embeds is forbidden. Convert it to a ternary operation instead'}
+    ]
+  }, {
+    code: '<div>{x ? <div>{y && <div />}</div> : null}</div>',
+    output: '<div>{x ? <div>{y && <div />}</div> : null}</div>',
+    errors: [
+      {message: 'Using && to condition JSX embeds is forbidden. Convert it to a ternary operation instead'}
+    ]
+  }]
+});