oxc/crates/oxc_traverse/scripts/lib/parse.mjs

import {readFile} from 'fs/promises';
import {join as pathJoin} from 'path';
import {fileURLToPath} from 'url';
import {typeAndWrappers} from './utils.mjs';

const FILENAMES = ['js.rs', 'jsx.rs', 'literal.rs', 'ts.rs'];

/**
 * Parse type defs from Rust files.
 */
export default async function getTypesFromCode() {
    const codeDirPath = pathJoin(fileURLToPath(import.meta.url), '../../../../oxc_ast/src/ast/');

    const types = Object.create(null);
    for (const filename of FILENAMES) {
        const code = await readFile(`${codeDirPath}${filename}`, 'utf8');
        parseFile(code, filename, types);
    }
    return types;
}

class Position {
    constructor(filename, index) {
        this.filename = filename;
        this.index = index;
    }

    assert(condition, message) {
        if (!condition) this.throw(message);
    }
    throw(message) {
        throw new Error(`${message || 'Unknown error'} (at ${this.filename}:${this.index + 1})`);
    }
}

class Lines {
    constructor(lines, filename, offset = 0) {
        this.lines = lines;
        this.filename = filename;
        this.offset = offset;
        this.index = 0;
    }

    static fromCode(code, filename) {
        const lines = code.split(/\r?\n/)
            .map(line => line.replace(/\s+/g, ' ').replace(/ ?\/\/.*$/, '').replace(/ $/, ''));
        return new Lines(lines, filename, 0);
    }

    child() {
        return new Lines([], this.filename, this.index);
    }

    current() {
        return this.lines[this.index];
    }
    next() {
        return this.lines[this.index++];
    }
    isEnd() {
        return this.index === this.lines.length;
    }

    position() {
        return new Position(this.filename, this.index + this.offset);
    }
    positionPrevious() {
        return new Position(this.filename, this.index + this.offset - 1);
    }
}

function parseFile(code, filename, types) {
    const lines = Lines.fromCode(code, filename);
    while (!lines.isEnd()) {
        if (lines.current() !== '#[visited_node]') {
            lines.next();
            continue;
        }

        // Consume attrs and comments, parse `#[scope]` attr
        let match, scopeArgs = null;
        while (!lines.isEnd()) {
            if (/^#\[scope[(\]]/.test(lines.current())) {
                scopeArgs = parseScopeArgs(lines, scopeArgs);
                continue;
            }
            match = lines.next().match(/^pub (enum|struct) ((.+?)(?:<'a>)?) \{/);
            if (match) break;
        }
        lines.position().assert(match, `Could not find enum or struct after #[visited_node]`);
        const [, kind, rawName, name] = match;

        // Find end of struct / enum
        const itemLines = lines.child();
        while (!lines.isEnd()) {
            const line = lines.next();
            if (line === '}') break;
            itemLines.lines.push(line.trim());
        }

        if (kind === 'struct') {
            types[name] = parseStruct(name, rawName, itemLines, scopeArgs);
        } else {
            types[name] = parseEnum(name, rawName, itemLines);
        }
    }
}

function parseStruct(name, rawName, lines, scopeArgs) {
    const fields = [];
    while (!lines.isEnd()) {
        let isScopeEntry = false, line;
        while (!lines.isEnd()) {
            line = lines.next();
            if (line === '') continue;
            if (line === '#[scope(enter_before)]') {
                isScopeEntry = true;
            } else if (line.startsWith('#[')) {
                while (!line.endsWith(']')) {
                    line = lines.next();
                }
            } else {
                break;
            }
        }

        const match = line.match(/^pub ((?:r#)?([a-z_]+)): (.+),$/);
        lines.positionPrevious().assert(match, `Cannot parse line as struct field: '${line}'`);
        const [, rawName, name, rawTypeName] = match,
            typeName = rawTypeName.replace(/<'a>/g, '').replace(/<'a, ?/g, '<'),
            {name: innerTypeName, wrappers} = typeAndWrappers(typeName);

        fields.push({name, typeName, rawName, rawTypeName, innerTypeName, wrappers});

        if (isScopeEntry) scopeArgs.enterScopeBefore = name;
    }
    return {kind: 'struct', name, rawName, fields, scopeArgs};
}

function parseEnum(name, rawName, lines) {
    const variants = [],
        inherits = [];
    while (!lines.isEnd()) {
        let line = lines.next();
        if (line === '') continue;
        if (line.startsWith('#[')) {
            while (!line.endsWith(']')) {
                line = lines.next();
            }
            continue;
        }

        const match = line.match(/^(.+?)\((.+?)\)(?: ?= ?(\d+))?,$/);
        if (match) {
            const [, name, rawTypeName, discriminantStr] = match,
                typeName = rawTypeName.replace(/<'a>/g, '').replace(/<'a, ?/g, '<'),
                {name: innerTypeName, wrappers} = typeAndWrappers(typeName),
                discriminant = discriminantStr ? +discriminantStr : null;
            variants.push({name, typeName, rawTypeName, innerTypeName, wrappers, discriminant});
        } else {
            const match2 = line.match(/^@inherit ([A-Za-z]+)$/);
            lines.positionPrevious().assert(match2, `Cannot parse line as enum variant: '${line}'`);
            inherits.push(match2[1]);
        }
    }
    return {kind: 'enum', name, rawName, variants, inherits};
}

function parseScopeArgs(lines, scopeArgs) {
    const position = lines.position();

    // Get whole of `#[scope]` attr text as a single line string
    let scopeArgsStr = '';
    let line = lines.next();
    if (line !== '#[scope]') {
        line = line.slice('#[scope('.length);
        while (!line.endsWith(')]')) {
            scopeArgsStr += ` ${line}`;
            line = lines.next();
        }
        scopeArgsStr += ` ${line.slice(0, -2)}`;
        scopeArgsStr = scopeArgsStr.trim().replace(/  +/g, ' ').replace(/,$/, '');
    }

    // Parse attr
    return parseScopeArgsStr(scopeArgsStr, scopeArgs, position);
}

function parseScopeArgsStr(argsStr, args, position) {
    if (!args) args = {flags: 'ScopeFlags::empty()', if: null, strictIf: null};

    if (!argsStr) return args;

    const matchAndConsume = (regex) => {
        const match = argsStr.match(regex);
        position.assert(match);
        argsStr = argsStr.slice(match[0].length);
        return match.slice(1);
    };

    try {
        while (true) {
            let [key] = matchAndConsume(/^([a-z_]+)\(/);
            key = key.replace(/_([a-z])/g, (_, c) => c.toUpperCase());
            position.assert(Object.hasOwn(args, key), `Unexpected scope macro arg: ${key}`);

            let bracketCount = 1,
                index = 0;
            for (; index < argsStr.length; index++) {
                const char = argsStr[index];
                if (char === '(') {
                    bracketCount++;
                } else if (char === ')') {
                    bracketCount--;
                    if (bracketCount === 0) break;
                }
            }
            position.assert(bracketCount === 0);

            args[key] = argsStr.slice(0, index).trim();
            argsStr = argsStr.slice(index + 1);
            if (argsStr === '') break;

            matchAndConsume(/^ ?, ?/);
        }
    } catch (err) {
        position.throw(`Cannot parse scope args: '${argsStr}': ${err?.message || 'Unknown error'}`);
    }

    return args;
}