Add no-irregular-whitespace

docs/user-guide/rules/list.md

@@ -395,3 +395,4 @@ Grouped first by the following categories and then by the [_thing_](http://apps.
 - [`no-missing-end-of-source-newline`](../../../lib/rules/no-missing-end-of-source-newline/README.md): Disallow missing end-of-source newlines (Autofixable).
 - [`no-empty-first-line`](../../../lib/rules/no-empty-first-line/README.md): Disallow empty first lines (Autofixable).
 - [`unicode-bom`](../../../lib/rules/unicode-bom/README.md): Require or disallow Unicode BOM.
+- [`no-irregular-whitespace`](../../../lib/rules/no-irregular-whitespace/README.md): Disallow irregular whitespace.

lib/rules/index.js

@@ -245,6 +245,7 @@ const rules = {
 	'no-invalid-position-at-import-rule': importLazy(() =>
 		require('./no-invalid-position-at-import-rule'),
 	)(),
+	'no-irregular-whitespace': importLazy(() => require('./no-irregular-whitespace'))(),
 	'no-missing-end-of-source-newline': importLazy(() =>
 		require('./no-missing-end-of-source-newline'),
 	)(),

lib/rules/no-irregular-whitespace/README.md

@@ -0,0 +1,57 @@
+# no-irregular-whitespace
+
+Disallow irregular whitespaces.
+
+<!-- prettier-ignore -->
+```css
+    .firstClass .secondClass {}
+/**            ↑
+ * Irregular whitespace. Selector would fail to match '.firstClass' */
+```
+
+## Options
+
+### `true`
+
+The following patterns are considered violations:
+
+<!-- prettier-ignore -->
+```css
+.firstClass .secondClass {}
+```
+
+The following patterns are _not_ considered violations:
+
+<!-- prettier-ignore -->
+```css
+.firstClass .secondClass { /* Writing comments with irregular whitespaces */ }
+```
+
+## Unicode reference of irregular whitespaces
+
+```
+\u000B - Line Tabulation (\v) - <VT>
+\u000C - Form Feed (\f) - <FF>
+\u00A0 - No-Break Space - <NBSP>
+\u0085 - Next Line
+\u1680 - Ogham Space Mark
+\u180E - Mongolian Vowel Separator - <MVS>
+\uFEFF - Zero Width No-Break Space - <BOM>
+\u2000 - En Quad
+\u2001 - Em Quad
+\u2002 - En Space - <ENSP>
+\u2003 - Em Space - <EMSP>
+\u2004 - Tree-Per-Em
+\u2005 - Four-Per-Em
+\u2006 - Six-Per-Em
+\u2007 - Figure Space
+\u2008 - Punctuation Space - <PUNCSP>
+\u2009 - Thin Space
+\u200A - Hair Space
+\u200B - Zero Width Space - <ZWSP>
+\u2028 - Line Separator
+\u2029 - Paragraph Separator
+\u202F - Narrow No-Break Space
+\u205F - Medium Mathematical Space
+\u3000 - Ideographic Space
+```

lib/rules/no-irregular-whitespace/__tests__/index.js

@@ -0,0 +1,98 @@
+'use strict';
+
+const { messages, ruleName } = require('..');
+
+const IRREGULAR_WHITESPACES = [
+	'\u000B', // Line Tabulation (\v) - <VT>
+	'\u000C', // Form Feed (\f) - <FF>
+	'\u00A0', // No-Break Space - <NBSP>
+	'\u0085', // Next Line
+	'\u1680', // Ogham Space Mark
+	'\u180E', // Mongolian Vowel Separator - <MVS>
+	'\uFEFF', // Zero Width No-Break Space - <BOM>
+	'\u2000', // En Quad
+	'\u2001', // Em Quad
+	'\u2002', // En Space - <ENSP>
+	'\u2003', // Em Space - <EMSP>
+	'\u2004', // Tree-Per-Em
+	'\u2005', // Four-Per-Em
+	'\u2006', // Six-Per-Em
+	'\u2007', // Figure Space
+	'\u2008', // Punctuation Space - <PUNCSP>
+	'\u2009', // Thin Space
+	'\u200A', // Hair Space
+	'\u200B', // Zero Width Space - <ZWSP>
+	'\u2028', // Line Separator
+	'\u2029', // Paragraph Separator
+	'\u202F', // Narrow No-Break Space
+	'\u205F', // Medium Mathematical Space
+	'\u3000', // Ideographic Space
+];
+
+const characterToUnicodeString = (str) =>
+	`\\u${str.charCodeAt(0).toString(16).toUpperCase().padStart(4, '0')}`;
+
+testRule({
+	ruleName,
+	config: true,
+	accept: [
+		{
+			code: ' ',
+			description: 'regular whitespace',
+		},
+		{
+			code: '\n',
+			description: 'new line',
+		},
+		{
+			code: '/* Irregular whitespace\nin multi line comments\nare allowed */',
+			description: 'irregular whitespace in multi line comments',
+		},
+	],
+
+	reject: [
+		{
+			code: '.firstClass .secondClass { color: pink; }',
+			description: 'irregular whitespace in selector',
+			message: messages.unexpected,
+			line: 1,
+			column: 12,
+		},
+		{
+			code: '.firstClass .secondClass  { color: pink; }',
+			description: 'irregular whitespace after selector',
+			message: messages.unexpected,
+			line: 1,
+			column: 26,
+		},
+		{
+			code: 'margin: 1rem 2rem;',
+			description: 'irregular whitespace in declaration value',
+			message: messages.unexpected,
+			line: 1,
+			column: 13,
+		},
+		{
+			code: 'margin: 1rem 2rem ;',
+			description: 'irregular whitespace after value',
+			message: messages.unexpected,
+			line: 1,
+			column: 18,
+		},
+		{
+			code: '$variable : 5rem;',
+			description: 'irregular whitespace in variable name',
+			message: messages.unexpected,
+			line: 1,
+			column: 10,
+		},
+		// Generic test for all types of irregular whitespaces.
+		...IRREGULAR_WHITESPACES.map((ws) => ({
+			code: `a[title="irregular${ws}whitespace"] { color: pink; }`,
+			description: `irregular whitespace in attribute selector: ${characterToUnicodeString(ws)}`,
+			message: messages.unexpected,
+			line: 1,
+			column: 19,
+		})),
+	],
+});

lib/rules/no-irregular-whitespace/index.js

@@ -0,0 +1,134 @@
+// @ts-nocheck
+
+'use strict';
+
+const report = require('../../utils/report');
+const ruleMessages = require('../../utils/ruleMessages');
+const validateOptions = require('../../utils/validateOptions');
+
+const ruleName = 'no-irregular-whitespace';
+const messages = ruleMessages(ruleName, {
+	unexpected: 'Unexpected irregular whitespace',
+});
+
+const IRREGULAR_WHITESPACES = [
+	'\u000B', // Line Tabulation (\v) - <VT>
+	'\u000C', // Form Feed (\f) - <FF>
+	'\u00A0', // No-Break Space - <NBSP>
+	'\u0085', // Next Line
+	'\u1680', // Ogham Space Mark
+	'\u180E', // Mongolian Vowel Separator - <MVS>
+	'\uFEFF', // Zero Width No-Break Space - <BOM>
+	'\u2000', // En Quad
+	'\u2001', // Em Quad
+	'\u2002', // En Space - <ENSP>
+	'\u2003', // Em Space - <EMSP>
+	'\u2004', // Tree-Per-Em
+	'\u2005', // Four-Per-Em
+	'\u2006', // Six-Per-Em
+	'\u2007', // Figure Space
+	'\u2008', // Punctuation Space - <PUNCSP>
+	'\u2009', // Thin Space
+	'\u200A', // Hair Space
+	'\u200B', // Zero Width Space - <ZWSP>
+	'\u2028', // Line Separator
+	'\u2029', // Paragraph Separator
+	'\u202F', // Narrow No-Break Space
+	'\u205F', // Medium Mathematical Space
+	'\u3000', // Ideographic Space
+];
+
+const IRREGULAR_WHITESPACES_PATTERN = new RegExp(`([${IRREGULAR_WHITESPACES.join('')}])`);
+
+const generateInvalidWhitespaceValidator = () => {
+	return (str) => typeof str === 'string' && IRREGULAR_WHITESPACES_PATTERN.exec(str);
+};
+
+const declarationSchema = {
+	prop: 'string',
+	value: 'string',
+	raws: {
+		before: 'string',
+		between: 'string',
+	},
+};
+
+const atRuleSchema = {
+	name: 'string',
+	params: 'string',
+	raws: {
+		before: 'string',
+		between: 'string',
+		afterName: 'string',
+		after: 'string',
+	},
+};
+
+const ruleSchema = {
+	selector: 'string',
+	raws: {
+		before: 'string',
+		between: 'string',
+		after: 'string',
+	},
+};
+
+const generateNodeValidator = (nodeSchema, validator) => {
+	const allKeys = Object.keys(nodeSchema);
+	const validatorForKey = {};
+
+	allKeys.forEach((key) => {
+		if (typeof nodeSchema[key] === 'string') validatorForKey[key] = validator;
+
+		if (typeof nodeSchema[key] === 'object')
+			validatorForKey[key] = generateNodeValidator(nodeSchema[key], validator);
+	});
+
+	// This will be called many times, so it's optimized for performance and not readibility.
+	// Surprisingly, this seem to be slightly faster then concatenating the params and running the validator once.
+	return (node) => {
+		for (const currentKey of allKeys) {
+			if (validatorForKey[currentKey](node[currentKey])) {
+				return validatorForKey[currentKey](node[currentKey]);
+			}
+		}
+	};
+};
+
+function rule(on) {
+	return (root, result) => {
+		const validOptions = validateOptions(result, ruleName, { actual: on });
+
+		if (!validOptions) {
+			return;
+		}
+
+		const genericValidator = generateInvalidWhitespaceValidator();
+
+		const validate = (node, validator) => {
+			const issue = validator(node);
+
+			if (issue) {
+				report({
+					ruleName,
+					result,
+					message: messages.unexpected,
+					node,
+					word: issue[1],
+				});
+			}
+		};
+
+		const atRuleValidator = generateNodeValidator(atRuleSchema, genericValidator);
+		const ruleValidator = generateNodeValidator(ruleSchema, genericValidator);
+		const declValidator = generateNodeValidator(declarationSchema, genericValidator);
+
+		root.walkAtRules((atRule) => validate(atRule, atRuleValidator));
+		root.walkRules((selector) => validate(selector, ruleValidator));
+		root.walkDecls((declaration) => validate(declaration, declValidator));
+	};
+}
+
+rule.ruleName = ruleName;
+rule.messages = messages;
+module.exports = rule;