feat: add lowercase

docs/rules/lowercase.md

@@ -0,0 +1,62 @@
+---
+id: lowercase
+title: "lowercase"
+---
+
+# lowercase
+
+Enforce to use lowercase for tag and attribute names.
+
+## How to use
+
+.eslintrc.js
+
+```js
+module.exports = {
+  rules: {
+    "@html-eslint/lowercase": "error",
+  },
+};
+```
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+<!-- prettier-ignore -->
+```html
+<Div></Div>
+```
+
+<!-- prettier-ignore -->
+```html
+<div ID="foo"></div>
+```
+
+<!-- prettier-ignore -->
+```html
+<SCRIPT></SCRIPT>
+```
+
+<!-- prettier-ignore -->
+```html
+<sTyle></sTyle>
+```
+
+Examples of **correct** code for this rule:
+
+```html
+<div></div>
+```
+
+```html
+<div id="foo"></div>
+```
+
+```html
+<script></script>
+```
+
+```html
+<style></style>
+```

packages/eslint-plugin/lib/rules/index.js

@@ -32,6 +32,7 @@ const noTrailingSpaces = require("./no-trailing-spaces");
 const requireAttrs = require("./require-attrs");
 const noRestrictedAttrValues = require("./no-restricted-attr-values");
 const noScriptStyleType = require("./no-script-style-type");
+const lowercase = require("./lowercase");
 
 module.exports = {
   "require-lang": requireLang,
@@ -68,4 +69,5 @@ module.exports = {
   "no-trailing-spaces": noTrailingSpaces,
   "no-restricted-attr-values": noRestrictedAttrValues,
   "no-script-style-type": noScriptStyleType,
+  lowercase: lowercase,
 };

packages/eslint-plugin/lib/rules/lowercase.js

@@ -0,0 +1,93 @@
+const { NODE_TYPES } = require("@html-eslint/parser");
+const { RULE_CATEGORY } = require("../constants");
+
+const MESSAGE_IDS = {
+  UNEXPECTED: "unexpected",
+};
+
+/**
+ * @type {Rule}
+ */
+module.exports = {
+  meta: {
+    type: "suggestion",
+
+    docs: {
+      description: "Enforce to use lowercase for tag and attribute names.",
+      category: RULE_CATEGORY.STYLE,
+      recommended: false,
+    },
+
+    fixable: "code",
+    schema: [],
+    messages: {
+      [MESSAGE_IDS.UNEXPECTED]: "'{{name}}' is not in lowercase.",
+    },
+  },
+
+  create(context) {
+    /**
+     * @param {TagNode | StyleTagNode | ScriptTagNode} node
+     */
+    function nameOf(node) {
+      if (node.type === NODE_TYPES.ScriptTag) return "script";
+      if (node.type === NODE_TYPES.StyleTag) return "style";
+      return node.name;
+    }
+
+    /**
+     * @param {TagNode | StyleTagNode | ScriptTagNode} node
+     */
+    function check(node) {
+      const raw = node.openStart.value.slice(1);
+      if (nameOf(node) !== raw) {
+        context.report({
+          node: node.openStart,
+          messageId: MESSAGE_IDS.UNEXPECTED,
+          data: {
+            name: raw,
+          },
+          fix(fixer) {
+            const name = nameOf(node);
+            const fixes = [
+              fixer.replaceTextRange(node.openStart.range, `<${name}`),
+            ];
+
+            if (node.close) {
+              fixes.push(
+                fixer.replaceTextRange(node.close.range, `</${name}>`)
+              );
+            }
+
+            return fixes;
+          },
+        });
+      }
+      if (node.attributes && node.attributes.length) {
+        node.attributes.forEach((attribute) => {
+          if (attribute.key.value !== attribute.key.value.toLowerCase()) {
+            context.report({
+              node: attribute.key,
+              messageId: MESSAGE_IDS.UNEXPECTED,
+              data: {
+                name: attribute.key.value,
+              },
+              fix(fixer) {
+                return fixer.replaceText(
+                  attribute.key,
+                  attribute.key.value.toLowerCase()
+                );
+              },
+            });
+          }
+        });
+      }
+    }
+
+    return {
+      Tag: check,
+      StyleTag: check,
+      ScriptTag: check,
+    };
+  },
+};

packages/eslint-plugin/tests/rules/lowercase.test.js

@@ -0,0 +1,68 @@
+const createRuleTester = require("../rule-tester");
+const rule = require("../../lib/rules/lowercase");
+
+const ruleTester = createRuleTester();
+
+ruleTester.run("lowercase", rule, {
+  valid: [
+    {
+      code: "<div></div>",
+    },
+    {
+      code: "<div id='foo'></div>",
+    },
+    {
+      code: "<script></script>",
+    },
+    {
+      code: "<style></style>",
+    },
+  ],
+  invalid: [
+    {
+      code: '<IMG src="img.png">',
+      output: '<img src="img.png">',
+      errors: [
+        {
+          message: "'IMG' is not in lowercase.",
+        },
+      ],
+    },
+    {
+      code: "<Script></Script>",
+      output: "<script></script>",
+      errors: [
+        {
+          message: "'Script' is not in lowercase.",
+        },
+      ],
+    },
+    {
+      code: "<Style type='text/css'></Style>",
+      output: "<style type='text/css'></style>",
+      errors: [
+        {
+          message: "'Style' is not in lowercase.",
+        },
+      ],
+    },
+    {
+      code: "<sTyle type='text/css'></sTyle>",
+      output: "<style type='text/css'></style>",
+      errors: [
+        {
+          message: "'sTyle' is not in lowercase.",
+        },
+      ],
+    },
+    {
+      code: "<div ID='1'></div>",
+      output: "<div id='1'></div>",
+      errors: [
+        {
+          message: "'ID' is not in lowercase.",
+        },
+      ],
+    },
+  ],
+});