Add string-content rule (#496)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

docs/rules/string-content.md

@@ -0,0 +1,78 @@
+# Enforce better string content
+
+Enforce certain things about the contents of strings. For example, you can enforce using `’` instead of `'` to avoid escaping. Or you could block some words. The possibilities are endless.
+
+This rule is fixable.
+
+*It only reports one pattern per AST node at the time.*
+
+## Fail
+
+```js
+const foo = 'Someone\'s coming!';
+```
+
+## Pass
+
+```js
+const foo = 'Someone’s coming!';
+```
+
+## Options
+
+Type: `object`
+
+### patterns
+
+Type: `object`
+
+Extend [default patterns](#default-pattern).
+
+The example below:
+
+- Disables the default `'` → `’` replacement.
+- Adds a custom `unicorn` → `🦄` replacement.
+- Adds a custom `awesome` → `😎` replacement and a custom message.
+- Adds a custom `cool` → `😎` replacement, but disables auto fix.
+
+```json
+{
+	"unicorn/string-content": [
+		"error",
+		{
+			"patterns": {
+				"'": false,
+				"unicorn": "🦄",
+				"awesome": {
+					"suggest": "😎",
+					"message": "Please use `😎` instead of `awesome`."
+				},
+				"cool": {
+					"suggest": "😎",
+					"fix": false
+				}
+			}
+		}
+	]
+}
+```
+
+The key of `patterns` is treated as a regex, so you must escape special characters.
+
+For example, if you want to enforce `...` → `…`:
+
+```json
+{
+	"patterns": {
+		"\\.\\.\\.": "…"
+	}
+}
+```
+
+## Default Pattern
+
+```json
+{
+	"'": "’"
+}
+```

index.js

@@ -64,6 +64,7 @@ module.exports = {
 				'unicorn/prefer-trim-start-end': 'error',
 				'unicorn/prefer-type-error': 'error',
 				'unicorn/prevent-abbreviations': 'error',
+				'unicorn/string-content': 'off',
 				'unicorn/throw-new-error': 'error'
 			}
 		}

readme.md

@@ -79,6 +79,7 @@ Configure it in `package.json`.
 			"unicorn/prefer-trim-start-end": "error",
 			"unicorn/prefer-type-error": "error",
 			"unicorn/prevent-abbreviations": "error",
+			"unicorn/string-content": "off",
 			"unicorn/throw-new-error": "error"
 		}
 	}
@@ -132,6 +133,7 @@ Configure it in `package.json`.
 - [prefer-trim-start-end](docs/rules/prefer-trim-start-end.md) - Prefer `String#trimStart()` / `String#trimEnd()` over `String#trimLeft()` / `String#trimRight()`. *(fixable)*
 - [prefer-type-error](docs/rules/prefer-type-error.md) - Enforce throwing `TypeError` in type checking conditions. *(fixable)*
 - [prevent-abbreviations](docs/rules/prevent-abbreviations.md) - Prevent abbreviations. *(partly fixable)*
+- [string-content](docs/rules/string-content.md) - Enforce better string content. *(fixable)*
 - [throw-new-error](docs/rules/throw-new-error.md) - Require `new` when throwing an error. *(fixable)*
 
 ## Deprecated Rules

rules/better-regex.js

@@ -62,17 +62,17 @@ const create = context => {
 			const newPattern = cleanRegexp(oldPattern, flags);
 
 			if (oldPattern !== newPattern) {
-				// Escape backslash
-				const fixed = quoteString(newPattern.replace(/\\/g, '\\\\'));
-
 				context.report({
 					node,
 					message,
 					data: {
 						original: oldPattern,
 						optimized: newPattern
 					},
-					fix: fixer => fixer.replaceText(patternNode, fixed)
+					fix: fixer => fixer.replaceText(
+						patternNode,
+						quoteString(newPattern)
+					)
 				});
 			}
 		}

rules/string-content.js

@@ -0,0 +1,157 @@
+'use strict';
+const getDocumentationUrl = require('./utils/get-documentation-url');
+const quoteString = require('./utils/quote-string');
+const replaceTemplateElement = require('./utils/replace-template-element');
+const escapeTemplateElementRaw = require('./utils/escape-template-element-raw');
+
+const defaultPatterns = {
+	'\'': '’'
+};
+
+const defaultMessage = 'Prefer `{{suggest}}` over `{{match}}`.';
+
+function getReplacements(patterns) {
+	return Object.entries({
+		...defaultPatterns,
+		...patterns
+	})
+		.filter(([, options]) => options !== false)
+		.map(([match, options]) => {
+			if (typeof options === 'string') {
+				options = {
+					suggest: options
+				};
+			}
+
+			return {
+				match,
+				regex: new RegExp(match, 'gu'),
+				fix: true,
+				...options
+			};
+		});
+}
+
+const create = context => {
+	const {patterns} = {
+		patterns: {},
+		...context.options[0]
+	};
+	const replacements = getReplacements(patterns);
+
+	if (replacements.length === 0) {
+		return {};
+	}
+
+	return {
+		'Literal, TemplateElement': node => {
+			const {type} = node;
+
+			let string;
+			if (type === 'Literal') {
+				string = node.value;
+				if (typeof string !== 'string') {
+					return;
+				}
+			} else {
+				string = node.value.raw;
+			}
+
+			if (!string) {
+				return;
+			}
+
+			const replacement = replacements.find(({regex}) => regex.test(string));
+
+			if (!replacement) {
+				return;
+			}
+
+			const {fix, message = defaultMessage, match, suggest} = replacement;
+			const problem = {
+				node,
+				message,
+				data: {
+					match,
+					suggest
+				}
+			};
+
+			if (!fix) {
+				context.report(problem);
+				return;
+			}
+
+			const fixed = string.replace(replacement.regex, suggest);
+			if (type === 'Literal') {
+				problem.fix = fixer => fixer.replaceText(
+					node,
+					quoteString(fixed, node.raw[0])
+				);
+			} else {
+				problem.fix = fixer => replaceTemplateElement(
+					fixer,
+					node,
+					escapeTemplateElementRaw(fixed)
+				);
+			}
+
+			context.report(problem);
+		}
+	};
+};
+
+const schema = [
+	{
+		type: 'object',
+		properties: {
+			patterns: {
+				type: 'object',
+				additionalProperties: {
+					anyOf: [
+						{
+							enum: [
+								false
+							]
+						},
+						{
+							type: 'string'
+						},
+						{
+							type: 'object',
+							required: [
+								'suggest'
+							],
+							properties: {
+								suggest: {
+									type: 'string'
+								},
+								fix: {
+									type: 'boolean'
+									// Default: true
+								},
+								message: {
+									type: 'string'
+									// Default: ''
+								}
+							},
+							additionalProperties: false
+						}
+					]
+				}}
+		},
+		additionalProperties: false
+	}
+];
+
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			url: getDocumentationUrl(__filename)
+		},
+		fixable: 'code',
+		schema
+	}
+};

rules/utils/escape-template-element-raw.js

@@ -0,0 +1,6 @@
+'use strict';
+
+module.exports = string => string.replace(
+	/(?<=(?:^|[^\\])(?:\\\\)*)(?<symbol>(?:`|\$(?={)))/g,
+	'\\$<symbol>'
+);

rules/utils/quote-string.js

@@ -1,9 +1,17 @@
 'use strict';
 
 /**
-Escape apostrophe and wrap the result in single quotes.
+Escape string and wrap the result in quotes.
 
 @param {string} string - The string to be quoted.
-@returns {string} - The quoted string.
+@param {string} quote - The quote character.
+@returns {string} - The quoted and escaped string.
 */
-module.exports = string => `'${string.replace(/'/g, '\\\'')}'`;
+module.exports = (string, quote = '\'') => {
+	const escaped = string
+		.replace(/\\/g, '\\\\')
+		.replace(/\r/g, '\\r')
+		.replace(/\n/g, '\\n')
+		.replace(new RegExp(quote, 'g'), `\\${quote}`);
+	return quote + escaped + quote;
+};

test/prefer-replace-all.js

@@ -86,7 +86,7 @@ ruleTester.run('prefer-replace-all', rule, {
 		},
 		{
 			code: 'foo.replace(/\\\\\\./g, bar)',
-			output: 'foo.replaceAll(\'\\.\', bar)',
+			output: 'foo.replaceAll(\'\\\\.\', bar)',
 			errors: [error]
 		}
 	]