Add new dom-elements-style-is-object rule (Fixes jsx-eslint#715)

Author: petersendidit

README.md

@@ -79,6 +79,7 @@ Finally, enable all of the rules that you would like to use.  Use [our preset](#
 
 # List of supported rules
 
+* [react/dom-elements-style-is-object](docs/rules/dom-elements-style-is-object.md): Enforce style prop value being an object
 * [react/display-name](docs/rules/display-name.md): Prevent missing `displayName` in a React component definition
 * [react/forbid-prop-types](docs/rules/forbid-prop-types.md): Forbid certain propTypes
 * [react/no-danger](docs/rules/no-danger.md): Prevent usage of dangerous JSX properties
@@ -155,6 +156,7 @@ See [ESLint documentation](http://eslint.org/docs/user-guide/configuring#extendi
 
 The rules enabled in this configuration are:
 
+* [react/dom-elements-style-is-object](docs/rules/dom-elements-style-is-object.md)
 * [react/display-name](docs/rules/display-name.md)
 * [react/jsx-no-duplicate-props](docs/rules/jsx-no-duplicate-props.md)
 * [react/jsx-no-undef](docs/rules/jsx-no-undef.md)

docs/rules/dom-elements-style-is-object.md

@@ -0,0 +1,59 @@
+# Enforce style prop value being an object (dom-elements-style-is-object)
+
+Require that the value of the prop `style` be an object or a variable that is
+an object.
+
+## Rule Details
+
+The property values of an object passed to the style prop must be strings.
+
+The following patterns are considered warnings:
+
+```jsx
+<div style="color: 'red'" />
+
+<div style={true} />
+
+<Hello style={true} />
+
+const styles = true;
+<div style={styles} />
+
+const styles = { height: 100 };
+<div style={styles} />
+```
+
+```js
+React.createElement("div", { style: "color: 'red'" });
+
+React.createElement("div", { style: true });
+
+React.createElement("Hello", { style: true });
+
+const styles = true;
+React.createElement("div", { style: styles });
+
+const styles = { height: 100 };
+React.createElement("div", { style: styles });
+```
+
+
+The following patterns are not considered warnings:
+
+```jsx
+<div style={{ color: "red" }} />
+
+<Hello style={{ color: "red" }} />
+
+const styles = { color: "red" };
+<div style={styles} />
+```
+
+```js
+React.createElement("div", { style: { color: 'red' }});
+
+React.createElement("Hello", { style: { color: 'red' }});
+
+const styles = { height: '100px' };
+React.createElement("div", { style: styles });
+```

index.js

@@ -52,7 +52,8 @@ var rules = {
   'jsx-no-target-blank': require('./lib/rules/jsx-no-target-blank'),
   'jsx-filename-extension': require('./lib/rules/jsx-filename-extension'),
   'require-optimization': require('./lib/rules/require-optimization'),
-  'no-find-dom-node': require('./lib/rules/no-find-dom-node')
+  'no-find-dom-node': require('./lib/rules/no-find-dom-node'),
+  'dom-elements-style-is-object': require('./lib/rules/dom-elements-style-is-object')
 };
 
 var ruleNames = Object.keys(rules);
@@ -72,6 +73,7 @@ module.exports = {
         }
       },
       rules: {
+        'react/dom-elements-style-is-object': 2,
         'react/display-name': 2,
         'react/jsx-no-duplicate-props': 2,
         'react/jsx-no-undef': 2,

lib/rules/dom-elements-style-is-object.js

@@ -0,0 +1,100 @@
+/**
+ * @fileoverview Enforce style prop value being an object and havng sting values
+ * @author David Petersen
+ */
+'use strict';
+
+var variableUtil = require('../util/variable');
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Enforce style prop value being an object and havng sting values',
+      category: '',
+      recommended: true
+    },
+    schema: []
+  },
+
+  create: function(context) {
+    /**
+     * @param {object} node A ObjectExpression node
+     */
+    function checkValuesAreStrings(node) {
+      node.properties.forEach(function(property) {
+        if (
+          property.value.type !== 'Literal'
+          || typeof property.value.value !== 'string'
+        ) {
+          context.report(property.value, 'Style object values must be strings');
+        }
+      });
+    }
+
+    /**
+     * @param {object} node A Identifier node
+     */
+    function checkIdentifiers(node) {
+      var variable = variableUtil.variablesInScope(context).find(function (item) {
+        return item.name === node.name;
+      });
+
+      if (!variable || !variable.defs[0].node.init) {
+        return;
+      }
+
+      if (variable.defs[0].node.init.type === 'Literal') {
+        context.report(node, 'Style prop value must be an object');
+      } else if (variable.defs[0].node.init.type === 'ObjectExpression') {
+        checkValuesAreStrings(variable.defs[0].node.init);
+      }
+    }
+
+    return {
+      CallExpression: function(node) {
+        if (
+          node.callee
+          && node.callee.type === 'MemberExpression'
+          && node.callee.property.name === 'createElement'
+          && node.arguments.length > 1
+        ) {
+          if (node.arguments[1].type === 'ObjectExpression') {
+            var style = node.arguments[1].properties.find(function(property) {
+              return property.key.name === 'style';
+            });
+            if (style) {
+              if (style.value.type === 'Identifier') {
+                checkIdentifiers(style.value);
+              } else if (style.value.type === 'Literal') {
+                context.report(style.value, 'Style prop value must be an object');
+              } else if (style.value.type === 'ObjectExpression') {
+                checkValuesAreStrings(style.value);
+              }
+            }
+          }
+        }
+      },
+
+      JSXAttribute: function(node) {
+        if (node.name.name !== 'style') {
+          return;
+        }
+
+        if (
+          node.value.type !== 'JSXExpressionContainer'
+          || node.value.expression.type === 'Literal'
+        ) {
+          context.report(node, 'Style prop value must be an object');
+        } else if (node.value.expression.type === 'ObjectExpression') {
+          checkValuesAreStrings(node.value.expression);
+        } else if (node.value.expression.type === 'Identifier') {
+          checkIdentifiers(node.value.expression);
+        }
+      }
+    };
+  }
+};