--- /dev/null
+/**
+ * @fileoverview Look for useless escapes in strings and regexes
+ * @author Onur Temizkan
+ */
+
+"use strict";
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/**
+ * Returns the union of two sets.
+ * @param {Set} setA The first set
+ * @param {Set} setB The second set
+ * @returns {Set} The union of the two sets
+ */
+function union(setA, setB) {
+ return new Set(function *() {
+ yield* setA;
+ yield* setB;
+ }());
+}
+
+const VALID_STRING_ESCAPES = union(new Set("\\nrvtbfux"), astUtils.LINEBREAKS);
+const REGEX_GENERAL_ESCAPES = new Set("\\bcdDfnpPrsStvwWxu0123456789]");
+const REGEX_NON_CHARCLASS_ESCAPES = union(REGEX_GENERAL_ESCAPES, new Set("^/.$*+?[{}|()Bk"));
+
+/**
+ * Parses a regular expression into a list of characters with character class info.
+ * @param {string} regExpText The raw text used to create the regular expression
+ * @returns {Object[]} A list of characters, each with info on escaping and whether they're in a character class.
+ * @example
+ *
+ * parseRegExp('a\\b[cd-]')
+ *
+ * returns:
+ * [
+ * {text: 'a', index: 0, escaped: false, inCharClass: false, startsCharClass: false, endsCharClass: false},
+ * {text: 'b', index: 2, escaped: true, inCharClass: false, startsCharClass: false, endsCharClass: false},
+ * {text: 'c', index: 4, escaped: false, inCharClass: true, startsCharClass: true, endsCharClass: false},
+ * {text: 'd', index: 5, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false},
+ * {text: '-', index: 6, escaped: false, inCharClass: true, startsCharClass: false, endsCharClass: false}
+ * ]
+ */
+function parseRegExp(regExpText) {
+ const charList = [];
+
+ regExpText.split("").reduce((state, char, index) => {
+ if (!state.escapeNextChar) {
+ if (char === "\\") {
+ return Object.assign(state, { escapeNextChar: true });
+ }
+ if (char === "[" && !state.inCharClass) {
+ return Object.assign(state, { inCharClass: true, startingCharClass: true });
+ }
+ if (char === "]" && state.inCharClass) {
+ if (charList.length && charList[charList.length - 1].inCharClass) {
+ charList[charList.length - 1].endsCharClass = true;
+ }
+ return Object.assign(state, { inCharClass: false, startingCharClass: false });
+ }
+ }
+ charList.push({
+ text: char,
+ index,
+ escaped: state.escapeNextChar,
+ inCharClass: state.inCharClass,
+ startsCharClass: state.startingCharClass,
+ endsCharClass: false
+ });
+ return Object.assign(state, { escapeNextChar: false, startingCharClass: false });
+ }, { escapeNextChar: false, inCharClass: false, startingCharClass: false });
+
+ return charList;
+}
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "disallow unnecessary escape characters",
+ category: "Best Practices",
+ recommended: true,
+ url: "https://eslint.org/docs/rules/no-useless-escape",
+ suggestion: true
+ },
+
+ messages: {
+ unnecessaryEscape: "Unnecessary escape character: \\{{character}}.",
+ removeEscape: "Remove the `\\`. This maintains the current functionality.",
+ escapeBackslash: "Replace the `\\` with `\\\\` to include the actual backslash character."
+ },
+
+ schema: []
+ },
+
+ create(context) {
+ const sourceCode = context.getSourceCode();
+
+ /**
+ * Reports a node
+ * @param {ASTNode} node The node to report
+ * @param {number} startOffset The backslash's offset from the start of the node
+ * @param {string} character The uselessly escaped character (not including the backslash)
+ * @returns {void}
+ */
+ function report(node, startOffset, character) {
+ const start = sourceCode.getLocFromIndex(sourceCode.getIndexFromLoc(node.loc.start) + startOffset);
+ const rangeStart = sourceCode.getIndexFromLoc(node.loc.start) + startOffset;
+ const range = [rangeStart, rangeStart + 1];
+
+ context.report({
+ node,
+ loc: {
+ start,
+ end: { line: start.line, column: start.column + 1 }
+ },
+ messageId: "unnecessaryEscape",
+ data: { character },
+ suggest: [
+ {
+ messageId: "removeEscape",
+ fix(fixer) {
+ return fixer.removeRange(range);
+ }
+ },
+ {
+ messageId: "escapeBackslash",
+ fix(fixer) {
+ return fixer.insertTextBeforeRange(range, "\\");
+ }
+ }
+ ]
+ });
+ }
+
+ /**
+ * Checks if the escape character in given string slice is unnecessary.
+ * @private
+ * @param {ASTNode} node node to validate.
+ * @param {string} match string slice to validate.
+ * @returns {void}
+ */
+ function validateString(node, match) {
+ const isTemplateElement = node.type === "TemplateElement";
+ const escapedChar = match[0][1];
+ let isUnnecessaryEscape = !VALID_STRING_ESCAPES.has(escapedChar);
+ let isQuoteEscape;
+
+ if (isTemplateElement) {
+ isQuoteEscape = escapedChar === "`";
+
+ if (escapedChar === "$") {
+
+ // Warn if `\$` is not followed by `{`
+ isUnnecessaryEscape = match.input[match.index + 2] !== "{";
+ } else if (escapedChar === "{") {
+
+ /*
+ * Warn if `\{` is not preceded by `$`. If preceded by `$`, escaping
+ * is necessary and the rule should not warn. If preceded by `/$`, the rule
+ * will warn for the `/$` instead, as it is the first unnecessarily escaped character.
+ */
+ isUnnecessaryEscape = match.input[match.index - 1] !== "$";
+ }
+ } else {
+ isQuoteEscape = escapedChar === node.raw[0];
+ }
+
+ if (isUnnecessaryEscape && !isQuoteEscape) {
+ report(node, match.index + 1, match[0].slice(1));
+ }
+ }
+
+ /**
+ * Checks if a node has an escape.
+ * @param {ASTNode} node node to check.
+ * @returns {void}
+ */
+ function check(node) {
+ const isTemplateElement = node.type === "TemplateElement";
+
+ if (
+ isTemplateElement &&
+ node.parent &&
+ node.parent.parent &&
+ node.parent.parent.type === "TaggedTemplateExpression" &&
+ node.parent === node.parent.parent.quasi
+ ) {
+
+ // Don't report tagged template literals, because the backslash character is accessible to the tag function.
+ return;
+ }
+
+ if (typeof node.value === "string" || isTemplateElement) {
+
+ /*
+ * JSXAttribute doesn't have any escape sequence: https://facebook.github.io/jsx/.
+ * In addition, backticks are not supported by JSX yet: https://github.com/facebook/jsx/issues/25.
+ */
+ if (node.parent.type === "JSXAttribute" || node.parent.type === "JSXElement" || node.parent.type === "JSXFragment") {
+ return;
+ }
+
+ const value = isTemplateElement ? node.value.raw : node.raw.slice(1, -1);
+ const pattern = /\\[^\d]/gu;
+ let match;
+
+ while ((match = pattern.exec(value))) {
+ validateString(node, match);
+ }
+ } else if (node.regex) {
+ parseRegExp(node.regex.pattern)
+
+ /*
+ * The '-' character is a special case, because it's only valid to escape it if it's in a character
+ * class, and is not at either edge of the character class. To account for this, don't consider '-'
+ * characters to be valid in general, and filter out '-' characters that appear in the middle of a
+ * character class.
+ */
+ .filter(charInfo => !(charInfo.text === "-" && charInfo.inCharClass && !charInfo.startsCharClass && !charInfo.endsCharClass))
+
+ /*
+ * The '^' character is also a special case; it must always be escaped outside of character classes, but
+ * it only needs to be escaped in character classes if it's at the beginning of the character class. To
+ * account for this, consider it to be a valid escape character outside of character classes, and filter
+ * out '^' characters that appear at the start of a character class.
+ */
+ .filter(charInfo => !(charInfo.text === "^" && charInfo.startsCharClass))
+
+ // Filter out characters that aren't escaped.
+ .filter(charInfo => charInfo.escaped)
+
+ // Filter out characters that are valid to escape, based on their position in the regular expression.
+ .filter(charInfo => !(charInfo.inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES).has(charInfo.text))
+
+ // Report all the remaining characters.
+ .forEach(charInfo => report(node, charInfo.index, charInfo.text));
+ }
+
+ }
+
+ return {
+ Literal: check,
+ TemplateElement: check
+ };
+ }
+};
projects / dotfiles / .git / blobdiff