Prevent adjacent inline elements not separated by whitespace.

CHANGELOG.md

@@ -2808,3 +2808,4 @@ If you're still not using React 15 you can keep the old behavior by setting the
 [`jsx-curly-newline`]: docs/rules/jsx-curly-newline.md
 [`jsx-no-useless-fragment`]: docs/rules/jsx-no-useless-fragment.md
 [`jsx-no-script-url`]: docs/rules/jsx-no-script-url.md
+[`no-adjacent-inline-elements`]: docs/rules/no-adjacent-inline-elements.md

docs/rules/no-adjacent-inline-elements.md

@@ -0,0 +1,24 @@
+# Prevent adjacent inline elements not separated by whitespace. (no-adjacent-inline-elements)
+
+Adjacent inline elements not separated by whitespace will bump up against each
+other when viewed in an unstyled manner, which usually isn't desirable.
+
+## Rule Details
+
+The following patterns are considered warnings:
+
+```jsx
+<div><a></a><a></a></div>
+<div><a></a><span></span></div>
+
+React.createElement("div", undefined, [React.createElement("a"), React.createElement("span")]);
+```
+
+The following patterns are not considered warnings:
+
+```jsx
+<div><div></div><div></div></div>
+<div><a></a> <a></a></div>
+
+React.createElement("div", undefined, [React.createElement("a"), " ", React.createElement("a")]);
+```

index.js

@@ -52,6 +52,7 @@ const allRules = {
   'jsx-uses-vars': require('./lib/rules/jsx-uses-vars'),
   'jsx-wrap-multilines': require('./lib/rules/jsx-wrap-multilines'),
   'no-access-state-in-setstate': require('./lib/rules/no-access-state-in-setstate'),
+  'no-adjacent-inline-elements': require('./lib/rules/no-adjacent-inline-elements'),
   'no-array-index-key': require('./lib/rules/no-array-index-key'),
   'no-children-prop': require('./lib/rules/no-children-prop'),
   'no-danger': require('./lib/rules/no-danger'),

lib/rules/no-adjacent-inline-elements.js

@@ -0,0 +1,115 @@
+/**
+ * @fileoverview Prevent adjacent inline elements not separated by whitespace.
+ * @author Sean Hayes
+ */
+
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Helpers
+// ------------------------------------------------------------------------------
+
+// https://developer.mozilla.org/en-US/docs/Web/HTML/Inline_elements
+const inlineNames = [
+  'a',
+  'b',
+  'big',
+  'i',
+  'small',
+  'tt',
+  'abbr',
+  'acronym',
+  'cite',
+  'code',
+  'dfn',
+  'em',
+  'kbd',
+  'strong',
+  'samp',
+  'time',
+  'var',
+  'bdo',
+  'br',
+  'img',
+  'map',
+  'object',
+  'q',
+  'script',
+  'span',
+  'sub',
+  'sup',
+  'button',
+  'input',
+  'label',
+  'select',
+  'textarea'
+];
+// Note: raw   will be transformed into \u00a0.
+const whitespaceRegex = /(?:^\s|\s$)/;
+
+function isInline(node) {
+  if (node.type === 'Literal') {
+    // Regular whitespace will be removed.
+    const value = node.value;
+    // To properly separate inline elements, each end of the literal will need
+    // whitespace.
+    return !whitespaceRegex.test(value);
+  }
+  if (node.type === 'JSXElement' && inlineNames.indexOf(node.openingElement.name.name) > -1) {
+    return true;
+  }
+  if (node.type === 'CallExpression' && inlineNames.indexOf(node.arguments[0].value) > -1) {
+    return true;
+  }
+  return false;
+}
+
+const ERROR = 'Child elements which render as inline HTML elements should be separated by a space or wrapped in block level elements.';
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  ERROR,
+  meta: {
+    docs: {
+      description: 'Prevent adjacent inline elements not separated by whitespace.',
+      category: 'Best Practices',
+      recommended: false
+    },
+    schema: []
+  },
+  create(context) {
+    function validate(node, children) {
+      let currentIsInline = false;
+      let previousIsInline = false;
+      for (let i = 0; i < children.length; i++) {
+        currentIsInline = isInline(children[i]);
+        if (previousIsInline && currentIsInline) {
+          context.report({
+            node,
+            message: ERROR
+          });
+          return;
+        }
+        previousIsInline = currentIsInline;
+      }
+    }
+    return {
+      JSXElement(node) {
+        validate(node, node.children);
+      },
+      CallExpression(node) {
+        if (!node.callee || node.callee.type !== 'MemberExpression' || node.callee.property.name !== 'createElement') {
+          return;
+        }
+        if (node.arguments.length < 2) {
+          return;
+        }
+        const children = node.arguments[2].elements;
+        validate(node, children);
+      }
+    };
+  }
+};

tests/lib/rules/no-adjacent-inline-elements.js

@@ -0,0 +1,102 @@
+/**
+ * @fileoverview Tests for no-adjacent-inline-elements
+ * @author Sean Hayes
+ */
+
+'use strict';
+
+// -----------------------------------------------------------------------------
+// Requirements
+// -----------------------------------------------------------------------------
+
+const RuleTester = require('eslint').RuleTester;
+const rule = require('../../../lib/rules/no-adjacent-inline-elements');
+
+const ERROR = rule.ERROR;
+
+const parserOptions = {
+  ecmaVersion: 6,
+  ecmaFeatures: {
+    experimentalObjectRestSpread: true,
+    jsx: true
+  }
+};
+
+// -----------------------------------------------------------------------------
+// Tests
+// -----------------------------------------------------------------------------
+
+const ruleTester = new RuleTester();
+ruleTester.run('no-adjacent-inline-elements', rule, {
+  valid: [
+    {
+      code: '<div />;',
+      parserOptions
+    },
+    {
+      code: '<div><div></div><div></div></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><p></p><div></div></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><p></p><a></a></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;<a></a></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;some text &nbsp; <a></a></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;some text <a></a></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><a></a> <a></a></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><ul><li><a></a></li><li><a></a></li></ul></div>;',
+      parserOptions
+    },
+    {
+      code: '<div><a></a> some text <a></a></div>;',
+      errors: [{message: ERROR}],
+      parserOptions
+    },
+    {
+      code: ('React.createElement("div", undefined, [React.createElement("a"), ' +
+        '" some text ", React.createElement("a")]);'),
+      errors: [{message: ERROR}],
+      parserOptions
+    },
+    {
+      code: 'React.createElement("div", undefined, [React.createElement("a"), " ", React.createElement("a")]);',
+      errors: [{message: ERROR}],
+      parserOptions
+    }
+  ],
+  invalid: [
+    {
+      code: '<div><a></a><a></a></div>;',
+      errors: [{message: ERROR}],
+      parserOptions
+    },
+    {
+      code: '<div><a></a><span></span></div>;',
+      errors: [{message: ERROR}],
+      parserOptions
+    },
+    {
+      code: 'React.createElement("div", undefined, [React.createElement("a"), React.createElement("span")]);',
+      errors: [{message: ERROR}],
+      parserOptions
+    }
+  ]
+});