├── .gitignore
├── src
    ├── tests
    │   ├── isCompName.test.js
    │   ├── tester.js
    │   └── validation.test.js
    └── index.js
├── package.json
└── readme.md


/.gitignore:
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1 | node_modules
2 | .DS_Store


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/src/tests/isCompName.test.js:
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1 | const { isCompName } = require('../index');
2 | 
3 | test('isCompName', () => {
4 | 	expect(isCompName('Foo')).toBe(true);
5 | 	expect(isCompName('foo')).toBe(false);
6 | });
7 | 


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/src/tests/tester.js:
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 1 | const { transform } = require('@babel/core');
 2 | const syntaxJSX = require('@babel/plugin-syntax-jsx');
 3 | const plugin = require('../index');
 4 | 
 5 | /**
 6 |  * @param {string} inputCode
 7 |  * @returns
 8 |  */
 9 | function testPlugin(inputCode) {
10 | 	return transform(inputCode, {
11 | 		plugins: [syntaxJSX, plugin],
12 | 	}).code;
13 | }
14 | 
15 | /**
16 |  * @param {string} inputCode
17 |  * @returns
18 |  */
19 | function testPluginWarnOnly(inputCode) {
20 | 	return transform(inputCode, {
21 | 		plugins: [syntaxJSX, [plugin, { warnOnly: true }]],
22 | 	}).code;
23 | }
24 | 
25 | module.exports = {
26 | 	testPlugin,
27 | 	testPluginWarnOnly,
28 | };
29 | 


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/package.json:
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 1 | {
 2 |   "name": "babel-plugin-validate-jsx-nesting",
 3 |   "version": "1.0.2",
 4 |   "description": "compile time JSX nesting validation",
 5 |   "main": "src/index.js",
 6 |   "scripts": {
 7 |     "test": "jest"
 8 |   },
 9 |   "keywords": [
10 |     "jsx validator",
11 |     "dom validator",
12 |     "html validator"
13 |   ],
14 |   "author": "Manan Tank",
15 |   "repository": {
16 |     "type": "git",
17 |     "url": "https://github.com/MananTank/validate-jsx-nesting.git"
18 |   },
19 |   "license": "ISC",
20 |   "devDependencies": {
21 |     "@babel/plugin-syntax-jsx": "^7.16.7",
22 |     "@types/jest": "^27.5.1",
23 |     "jest": "^28.1.0"
24 |   },
25 |   "dependencies": {
26 |     "@babel/core": "^7.17.10",
27 |     "validate-html-nesting": "^1.2.2"
28 |   },
29 |   "peerDependencies": {
30 |     "@babel/plugin-syntax-jsx": "latest"
31 |   }
32 | }


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/src/tests/validation.test.js:
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 1 | const { testPlugin, testPluginWarnOnly } = require('./tester');
 2 | 
 3 | // validation logic is tested in `validate-html-nesting` package
 4 | 
 5 | test('elements are tested', () => {
 6 | 	expect(() => testPlugin('<form> <form> </form> </form>')).toThrowError(
 7 | 		'<form> can not be child of <form>'
 8 | 	);
 9 | 
10 | 	expect(() => testPlugin('<p> <hr/> </p>')).toThrowError('<hr> can not be child of <p>');
11 | 	expect(() => testPlugin('<p> <a> </a> </p>')).not.toThrow();
12 | });
13 | 
14 | test('components are ignored', () => {
15 | 	expect(() => testPlugin('<Form> <form> </form> </Form>')).not.toThrow();
16 | 	expect(() => testPlugin('<Foo.bar> <form> </form> </Foo.bar>')).not.toThrow();
17 | });
18 | 
19 | test('warn only mode', () => {
20 | 	jest.spyOn(console, 'warn').mockImplementation();
21 | 
22 | 	expect(() => testPluginWarnOnly('<form> <form> </form> </form>')).not.toThrow();
23 | 
24 | 	expect(console.warn).toHaveBeenCalledWith(
25 | 		expect.stringContaining('<form> can not be child of <form>')
26 | 	);
27 | });
28 | 


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/readme.md:
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 1 | # babel-plugin-validate-jsx-nesting
 2 | 
 3 | ### Compile time JSX nesting validation
 4 | 
 5 | Example
 6 | 
 7 | ```html
 8 | Failed to Compile.
 9 | 
10 | Error: Invalid HTML nesting: <hr> can not be child of <p>
11 |   1 | <p>
12 |   2 |   <span> Hello </span>
13 | > 3 |   <hr />
14 |     |   ^^^^^^
15 |   4 |   <span> World </span>
16 |   5 | </p>
17 |   6 |
18 | ```
19 | 
20 | <br />
21 | 
22 | ### Why this validation is important?
23 | 
24 | without such validation, when JSX is converted to HTML and rendered in the DOM, the Browser will try to fix the invalid nestings ( such as `<hr>` inside `<p>` ) and thus the rendered DOM will have a different structure than JSX structure.
25 | 
26 | This is a big issue for frameworks that rely on JSX rendering the exact same elements in DOM. This can lead to unexpected behaviors.
27 | 
28 | <br />
29 | 
30 | ### Validation library
31 | 
32 | This babel plugin uses the [validate-html-nesting](https://github.com/MananTank/validate-html-nesting) library for validating HTML element nesting
33 | 
34 | <br />
35 | 
36 | ## Install
37 | 
38 | ```
39 | npm i -D babel-plugin-validate-jsx-nesting
40 | ```
41 | 
42 | <br />
43 | 
44 | ## babel config
45 | 
46 | Refer to the [babel config](https://babeljs.io/docs/en/configuration) guide to learn about configuring babel
47 | 
48 | ## no options
49 | 
50 | with this config, the plugin throws an error when invalid JSX nesting is found
51 | 
52 | ```json
53 | {
54 | 	"plugins": ["validate-jsx-nesting"]
55 | }
56 | ```
57 | 
58 | <br />
59 | 
60 | ### with `warnOnly: true` option
61 | 
62 | With this config, the plugin logs a warning when invalid JSX nesting is found
63 | 
64 | ```json
65 | {
66 | 	"plugins": [["validate-jsx-nesting", { "warnOnly": true }]]
67 | }
68 | ```
69 | 


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/src/index.js:
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 1 | const { isValidHTMLNesting } = require('validate-html-nesting');
 2 | 
 3 | /** @typedef {{ warnOnly: boolean} | undefined} PluginOptions */
 4 | 
 5 | /**
 6 |  * returns true if the tag is component's name
 7 |  * @param {string} tag
 8 |  * @returns
 9 |  */
10 | 
11 | function isCompName(tag) {
12 | 	return tag[0] === tag[0].toUpperCase();
13 | }
14 | 
15 | /**
16 |  * jsx nesting validator plugin
17 |  * @param {import('@babel/core')} babel
18 |  */
19 | module.exports = function (babel) {
20 | 	const { types: t } = babel;
21 | 
22 | 	/**
23 | 	 * @type {import('@babel/core').Visitor<{}>} path
24 | 	 */
25 | 	const domValidator = {
26 | 		JSXElement(path, state) {
27 | 			const elName = path.node.openingElement.name;
28 | 			if (t.isJSXIdentifier(elName)) {
29 | 				const elTagName = elName.name;
30 | 				// if not a component
31 | 				if (!isCompName(elTagName)) {
32 | 					const parent = path.parent;
33 | 					if (t.isJSXElement(parent)) {
34 | 						const parentElName = parent.openingElement.name;
35 | 						if (t.isJSXIdentifier(parentElName)) {
36 | 							const parentElTagName = parentElName.name;
37 | 							// if parent is not a component
38 | 							if (!isCompName(parentElTagName)) {
39 | 								if (!isValidHTMLNesting(parentElName.name, elName.name)) {
40 | 									// @ts-ignore
41 | 									const pluginOptions = /** @type {PluginOptions} */ (state && state.opts);
42 | 
43 | 									const error = path.buildCodeFrameError(
44 | 										`Invalid HTML nesting: <${elName.name}> can not be child of <${parentElName.name}>`
45 | 									);
46 | 
47 | 									if (pluginOptions && pluginOptions.warnOnly) {
48 | 										console.warn(error.message);
49 | 									} else {
50 | 										throw error;
51 | 									}
52 | 								}
53 | 							}
54 | 						}
55 | 					}
56 | 				}
57 | 			}
58 | 		},
59 | 	};
60 | 
61 | 	return {
62 | 		name: 'validate-jsx-nesting', // not required
63 | 		visitor: domValidator,
64 | 	};
65 | };
66 | 
67 | module.exports.isCompName = isCompName;
68 | 


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