prefer-named-capture-group.js

/**
 * @fileoverview Rule to enforce requiring named capture groups in regular expression.
 * @author Pig Fang <https://github.com/g-plane>
 */

"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const {
    CALL,
    CONSTRUCT,
    ReferenceTracker,
    getStringIfConstant
} = require("@eslint-community/eslint-utils");
const regexpp = require("@eslint-community/regexpp");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

const parser = new regexpp.RegExpParser();

/**
 * Creates fixer suggestions for the regex, if statically determinable.
 * @param {number} groupStart Starting index of the regex group.
 * @param {string} pattern The regular expression pattern to be checked.
 * @param {string} rawText Source text of the regexNode.
 * @param {ASTNode} regexNode AST node which contains the regular expression.
 * @returns {Array<SuggestionResult>} Fixer suggestions for the regex, if statically determinable.
 */
function suggestIfPossible(groupStart, pattern, rawText, regexNode) {
    switch (regexNode.type) {
        case "Literal":
            if (typeof regexNode.value === "string" && rawText.includes("\\")) {
                return null;
            }
            break;
        case "TemplateLiteral":
            if (regexNode.expressions.length || rawText.slice(1, -1) !== pattern) {
                return null;
            }
            break;
        default:
            return null;
    }

    const start = regexNode.range[0] + groupStart + 2;

    return [
        {
            fix(fixer) {
                const existingTemps = pattern.match(/temp\d+/gu) || [];
                const highestTempCount = existingTemps.reduce(
                    (previous, next) =>
                        Math.max(previous, Number(next.slice("temp".length))),
                    0
                );

                return fixer.insertTextBeforeRange(
                    [start, start],
                    `?<temp${highestTempCount + 1}>`
                );
            },
            messageId: "addGroupName"
        },
        {
            fix(fixer) {
                return fixer.insertTextBeforeRange(
                    [start, start],
                    "?:"
                );
            },
            messageId: "addNonCapture"
        }
    ];
}

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

/** @type {import('../shared/types').Rule} */
module.exports = {
    meta: {
        type: "suggestion",

        docs: {
            description: "Enforce using named capture group in regular expression",
            recommended: false,
            url: "https://eslint.org/docs/rules/prefer-named-capture-group"
        },

        hasSuggestions: true,

        schema: [],

        messages: {
            addGroupName: "Add name to capture group.",
            addNonCapture: "Convert group to non-capturing.",
            required: "Capture group '{{group}}' should be converted to a named or non-capturing group."
        }
    },

    create(context) {
        const sourceCode = context.getSourceCode();

        /**
         * Function to check regular expression.
         * @param {string} pattern The regular expression pattern to be checked.
         * @param {ASTNode} node AST node which contains the regular expression or a call/new expression.
         * @param {ASTNode} regexNode AST node which contains the regular expression.
         * @param {boolean} uFlag Flag indicates whether unicode mode is enabled or not.
         * @returns {void}
         */
        function checkRegex(pattern, node, regexNode, uFlag) {
            let ast;

            try {
                ast = parser.parsePattern(pattern, 0, pattern.length, uFlag);
            } catch {

                // ignore regex syntax errors
                return;
            }

            regexpp.visitRegExpAST(ast, {
                onCapturingGroupEnter(group) {
                    if (!group.name) {
                        const rawText = sourceCode.getText(regexNode);
                        const suggest = suggestIfPossible(group.start, pattern, rawText, regexNode);

                        context.report({
                            node,
                            messageId: "required",
                            data: {
                                group: group.raw
                            },
                            suggest
                        });
                    }
                }
            });
        }

        return {
            Literal(node) {
                if (node.regex) {
                    checkRegex(node.regex.pattern, node, node, node.regex.flags.includes("u"));
                }
            },
            Program() {
                const scope = context.getScope();
                const tracker = new ReferenceTracker(scope);
                const traceMap = {
                    RegExp: {
                        [CALL]: true,
                        [CONSTRUCT]: true
                    }
                };

                for (const { node } of tracker.iterateGlobalReferences(traceMap)) {
                    const regex = getStringIfConstant(node.arguments[0]);
                    const flags = getStringIfConstant(node.arguments[1]);

                    if (regex) {
                        checkRegex(regex, node, node.arguments[0], flags && flags.includes("u"));
                    }
                }
            }
        };
    }
};