no-octal.ts

import type { RegExpVisitor } from "@eslint-community/regexpp/visitor"
import type { RegExpContext } from "../utils"
import { createRule, defineRegexpVisitor } from "../utils"
import { isOctalEscape } from "../utils/regex-syntax"

export default createRule("no-octal", {
    meta: {
        docs: {
            description: "disallow octal escape sequence",
            category: "Best Practices",
            recommended: false, //  `regexp/strict` rule meets this rule.
        },
        schema: [],
        messages: {
            unexpected: "Unexpected octal escape sequence '{{expr}}'.",
            replaceHex:
                "Replace the octal escape sequence with a hexadecimal escape sequence.",
        },
        type: "suggestion", // "problem",
        hasSuggestions: true,
    },
    create(context) {
        function createVisitor({
            node,
            fixReplaceNode,
            getRegexpLocation,
        }: RegExpContext): RegExpVisitor.Handlers {
            return {
                onCharacterEnter(cNode) {
                    if (cNode.raw === "\\0") {
                        // \0 looks like a octal escape but is allowed
                        return
                    }
                    if (!isOctalEscape(cNode.raw)) {
                        // not an octal escape
                        return
                    }

                    const report =
                        // always report octal escapes that look like \0
                        cNode.raw.startsWith("\\0") ||
                        // don't report octal escapes inside character classes
                        // (e.g. [\4-\6]).
                        !(
                            cNode.parent.type === "CharacterClass" ||
                            cNode.parent.type === "CharacterClassRange"
                        )

                    if (report) {
                        context.report({
                            node,
                            loc: getRegexpLocation(cNode),
                            messageId: "unexpected",
                            data: {
                                expr: cNode.raw,
                            },
                            suggest: [
                                {
                                    messageId: "replaceHex",
                                    fix: fixReplaceNode(cNode, () => {
                                        return `\\x${cNode.value
                                            .toString(16)
                                            .padStart(2, "0")}`
                                    }),
                                },
                            ],
                        })
                    }
                },
            }
        }

        return defineRegexpVisitor(context, {
            createVisitor,
        })
    },
})