From e82018cb485c1acc133537a2df702f5704f83f8c Mon Sep 17 00:00:00 2001
From: Sean Hayes <gasphynx@gmail.com>
Date: Wed, 19 Apr 2017 13:13:13 -0700
Subject: [PATCH] Prevent adjacent inline elements not separated by whitespace.

---
 index.js                                      |   3 +-
 lib/rules/no-adjacent-inline-elements.js      | 118 ++++++++++++++++++
 .../lib/rules/no-adjacent-inline-elements.js  | 102 +++++++++++++++
 3 files changed, 222 insertions(+), 1 deletion(-)
 create mode 100644 lib/rules/no-adjacent-inline-elements.js
 create mode 100644 tests/lib/rules/no-adjacent-inline-elements.js

diff --git a/index.js b/index.js
index 9fd15e15bf..3074bbc5fa 100644
--- a/index.js
+++ b/index.js
@@ -64,7 +64,8 @@ var allRules = {
   'no-comment-textnodes': require('./lib/rules/no-comment-textnodes'),
   'require-extension': require('./lib/rules/require-extension'),
   'wrap-multilines': require('./lib/rules/wrap-multilines'),
-  'jsx-tag-spacing': require('./lib/rules/jsx-tag-spacing')
+  'jsx-tag-spacing': require('./lib/rules/jsx-tag-spacing'),
+  'no-adjacent-inline-elements': require('./lib/rules/no-adjacent-inline-elements')
 };
 
 function filterRules(rules, predicate) {
diff --git a/lib/rules/no-adjacent-inline-elements.js b/lib/rules/no-adjacent-inline-elements.js
new file mode 100644
index 0000000000..27afeb73b4
--- /dev/null
+++ b/lib/rules/no-adjacent-inline-elements.js
@@ -0,0 +1,118 @@
+/**
+ * @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
+var 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 &nbsp; will be transformed into \u00a0.
+var whitespaceStart = /^\s/;
+var whitespaceEnd = /\s$/;
+
+function isInline(node) {
+  if (node.type === 'Literal') {
+    // Regular whitespace will be removed.
+    var value = node.value;
+    // To properly separate inline elements, each end of the literal will need
+    // whitespace.
+    return !whitespaceStart.test(value) || !whitespaceEnd.test(value);
+  } else if (node.type === 'JSXElement') {
+    if (inlineNames.indexOf(node.openingElement.name.name) > -1) {
+      return true;
+    }
+  } else if (node.type === 'CallExpression') {
+    if (inlineNames.indexOf(node.arguments[0].value) > -1) {
+      return true;
+    }
+  }
+  return false;
+}
+
+var 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: ERROR,
+  meta: {
+    docs: {
+      description: 'Prevent adjacent inline elements not separated by whitespace.',
+      category: 'Best Practices',
+      recommended: false
+    },
+    schema: []
+  },
+  create: function(context) {
+    function validate(node, children) {
+      var currentIsInline = false;
+      var previousIsInline = false;
+      for (var i = 0; i < children.length; i++) {
+        currentIsInline = isInline(children[i]);
+        if (previousIsInline && currentIsInline) {
+          context.report({
+            node: node,
+            message: ERROR
+          });
+          return;
+        }
+        previousIsInline = currentIsInline;
+      }
+    }
+    return {
+      JSXElement: function(node) {
+        validate(node, node.children);
+      },
+      CallExpression: function(node) {
+        if (!node.callee || node.callee.type !== 'MemberExpression' || node.callee.property.name !== 'createElement') {
+          return;
+        }
+        if (node.arguments.length < 2) {
+          return;
+        }
+        var children = node.arguments[2].elements;
+        validate(node, children);
+      }
+    };
+  }
+};
diff --git a/tests/lib/rules/no-adjacent-inline-elements.js b/tests/lib/rules/no-adjacent-inline-elements.js
new file mode 100644
index 0000000000..07f4d0abab
--- /dev/null
+++ b/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
+// -----------------------------------------------------------------------------
+
+var rule = require('../../../lib/rules/no-adjacent-inline-elements');
+var RuleTester = require('eslint').RuleTester;
+
+var ERROR = rule.ERROR;
+
+var parserOptions = {
+  ecmaVersion: 6,
+  ecmaFeatures: {
+    experimentalObjectRestSpread: true,
+    jsx: true
+  }
+};
+
+// -----------------------------------------------------------------------------
+// Tests
+// -----------------------------------------------------------------------------
+
+var ruleTester = new RuleTester();
+ruleTester.run('no-adjacent-inline-elements', rule, {
+  valid: [
+    {
+      code: '<div />;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><div></div><div></div></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><p></p><div></div></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><p></p><a></a></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;<a></a></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;some text &nbsp; <a></a></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a>&nbsp;some text <a></a></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a> <a></a></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><ul><li><a></a></li><li><a></a></li></ul></div>;',
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a> some text <a></a></div>;',
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    },
+    {
+      code: ('React.createElement("div", undefined, [React.createElement("a"), ' +
+        '" some text ", React.createElement("a")]);'),
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    },
+    {
+      code: 'React.createElement("div", undefined, [React.createElement("a"), " ", React.createElement("a")]);',
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    }
+  ],
+  invalid: [
+    {
+      code: '<div><a></a><a></a></div>;',
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    },
+    {
+      code: '<div><a></a><span></span></div>;',
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    },
+    {
+      code: 'React.createElement("div", undefined, [React.createElement("a"), React.createElement("span")]);',
+      errors: [{message: ERROR}],
+      parserOptions: parserOptions
+    }
+  ]
+});