module.ts

/**
 * This is a custom implementation for the module system for evaluating code,
 * used for resolving values for dependencies interpolated in `css` or `styled`.
 *
 * This serves 2 purposes:
 * - Avoid leakage from evaluated code to module cache in current context, e.g. `babel-register`
 * - Allow us to invalidate the module cache without affecting other stuff, necessary for rebuilds
 *
 * We also use it to transpile the code with Babel by default.
 * We also store source maps for it to provide correct error stacktraces.
 *
 */

import fs from 'fs';
import NativeModule from 'module';
import path from 'path';
import vm from 'vm';

import type { BabelFileResult } from '@babel/core';

import type { CustomDebug } from '@linaria/logger';
import { createCustomDebug } from '@linaria/logger';
import type { BaseProcessor } from '@linaria/tags';
import type { StrictOptions } from '@linaria/utils';
import { getFileIdx } from '@linaria/utils';

import { TransformCacheCollection } from './cache';
import * as process from './process';

type HiddenModuleMembers = {
  _extensions: { [key: string]: () => void };
  _nodeModulePaths(filename: string): string[];
  _resolveFilename: (
    id: string,
    options: { id: string; filename: string; paths: string[] }
  ) => string;
};

export const DefaultModuleImplementation = NativeModule as typeof NativeModule &
  HiddenModuleMembers;

// Supported node builtins based on the modules polyfilled by webpack
// `true` means module is polyfilled, `false` means module is empty
const builtins = {
  assert: true,
  buffer: true,
  child_process: false,
  cluster: false,
  console: true,
  constants: true,
  crypto: true,
  dgram: false,
  dns: false,
  domain: true,
  events: true,
  fs: false,
  http: true,
  https: true,
  module: false,
  net: false,
  os: true,
  path: true,
  punycode: true,
  process: true,
  querystring: true,
  readline: false,
  repl: false,
  stream: true,
  string_decoder: true,
  sys: true,
  timers: true,
  tls: false,
  tty: true,
  url: true,
  util: true,
  vm: true,
  zlib: true,
};

const VALUES = Symbol('values');

const isProxy = (
  obj: unknown
): obj is { [VALUES]: Record<string | symbol, unknown> } =>
  typeof obj === 'object' && obj !== null && VALUES in obj;

const NOOP = () => {};

const padStart = (num: number, len: number) =>
  num.toString(10).padStart(len, '0');

const hasKey = <TKey extends string | symbol>(
  obj: unknown,
  key: TKey
): obj is Record<TKey, unknown> =>
  (typeof obj === 'object' || typeof obj === 'function') &&
  obj !== null &&
  key in obj;

class Module {
  #isEvaluated = false;

  #exports: Record<string, unknown> | unknown;

  #lazyValues: Map<string | symbol, () => unknown>;

  readonly idx: number;

  id: string;

  filename: string;

  imports: Map<string, string[]> | null;

  // paths: string[];

  extensions: string[];

  dependencies: string[] | null;

  tagProcessors: BaseProcessor[] = [];

  transform: ((text: string) => BabelFileResult | null) | null;

  debug: CustomDebug;

  constructor(
    filename: string,
    public options: Pick<StrictOptions, 'extensions'>,
    private cache = new TransformCacheCollection(),
    private debuggerDepth = 0,
    private parentModule?: Module,
    private moduleImpl: HiddenModuleMembers = DefaultModuleImplementation
  ) {
    this.idx = getFileIdx(filename);
    this.id = filename;
    this.filename = filename;
    this.imports = null;
    this.dependencies = null;
    this.transform = null;
    this.debug = createCustomDebug('module', this.idx);

    this.#lazyValues = new Map();

    const exports: Record<string | symbol, unknown> = {};

    this.#exports = new Proxy(exports, {
      get: (target, key) => {
        if (key === VALUES) {
          const values: Record<string | symbol, unknown> = {};
          this.#lazyValues.forEach((v, k) => {
            values[k] = v();
          });

          return values;
        }
        let value: unknown;
        if (this.#lazyValues.has(key)) {
          value = this.#lazyValues.get(key)?.();
        } else {
          // Support Object.prototype methods on `exports`
          // e.g `exports.hasOwnProperty`
          value = Reflect.get(target, key);
        }

        if (value === undefined && this.#lazyValues.has('default')) {
          const defaultValue = this.#lazyValues.get('default')?.();
          if (hasKey(defaultValue, key)) {
            this.debug(
              'evaluated',
              '⚠️  %s has been found in `default`. It indicates that ESM to CJS conversion of %s went wrong.',
              key,
              filename
            );
            value = defaultValue[key];
          }
        }

        this.debug('evaluated', 'get %s: %o', key, value);
        return value;
      },
      has: (target, key) => {
        if (key === VALUES) return true;
        return this.#lazyValues.has(key);
      },
      ownKeys: () => {
        return Array.from(this.#lazyValues.keys());
      },
      set: (target, key, value) => {
        if (key !== '__esModule') {
          this.debug('evaluated', 'set %s: %o', key, value);
        }

        if (value !== undefined) {
          this.#lazyValues.set(key, () => value);
        }

        return true;
      },
      defineProperty: (target, key, descriptor) => {
        const { value } = descriptor;
        if (value !== undefined) {
          this.#lazyValues.set(key, () => value);

          if (key !== '__esModule') {
            this.debug(
              'evaluated',
              'defineProperty %s with value %o',
              key,
              value
            );
          }

          this.#lazyValues.set(key, () => value);

          return true;
        }

        if ('get' in descriptor) {
          this.#lazyValues.set(key, descriptor.get!);
          this.debug('evaluated', 'defineProperty %s with getter', key);
        }

        return true;
      },
      getOwnPropertyDescriptor: (target, key) => {
        if (this.#lazyValues.has(key))
          return {
            enumerable: true,
            configurable: true,
          };

        return undefined;
      },
    });

    this.extensions = options.extensions;
    this.debug('init', filename);
  }

  public get exports() {
    return this.#exports;
  }

  public set exports(value) {
    if (isProxy(value)) {
      this.#exports = value[VALUES];
    } else {
      this.#exports = value;
    }

    this.debug(
      'evaluated',
      'the whole exports was overridden with %O',
      this.#exports
    );
  }

  resolve = (id: string) => {
    const resolveCacheKey = `${this.filename} -> ${id}`;
    if (this.cache.resolveCache.has(resolveCacheKey)) {
      return this.cache.resolveCache.get(resolveCacheKey)!;
    }

    const extensions = this.moduleImpl._extensions;
    const added: string[] = [];

    try {
      // Check for supported extensions
      this.extensions.forEach((ext) => {
        if (ext in extensions) {
          return;
        }

        // When an extension is not supported, add it
        // And keep track of it to clean it up after resolving
        // Use noop for the transform function since we handle it
        extensions[ext] = NOOP;
        added.push(ext);
      });

      const { filename } = this;

      return this.moduleImpl._resolveFilename(id, {
        id: filename,
        filename,
        paths: this.moduleImpl._nodeModulePaths(path.dirname(filename)),
      });
    } finally {
      // Cleanup the extensions we added to restore previous behaviour
      added.forEach((ext) => delete extensions[ext]);
    }
  };

  require: {
    (id: string): unknown;
    resolve: (id: string) => string;
    ensure: () => void;
  } = Object.assign(
    (id: string) => {
      if (id in builtins) {
        // The module is in the allowed list of builtin node modules
        // Ideally we should prevent importing them, but webpack polyfills some
        // So we check for the list of polyfills to determine which ones to support
        if (builtins[id as keyof typeof builtins]) {
          this.debug('require', `builtin '${id}'`);
          return require(id);
        }

        return null;
      }

      // Resolve module id (and filename) relatively to parent module
      const resolved = this.resolve(id);
      const [filename, onlyList] = resolved.split('\0');
      if (filename === id && !path.isAbsolute(id)) {
        // The module is a builtin node modules, but not in the allowed list
        throw new Error(
          `Unable to import "${id}". Importing Node builtins is not supported in the sandbox.`
        );
      }

      this.dependencies?.push(id);

      let m: Module;

      this.debug('require', `${id} -> ${filename}`);

      if (this.cache.evalCache.has(filename)) {
        m = this.cache.evalCache.get(filename)!;
        this.debug('eval-cache', '✅ %r has been gotten from cache', {
          namespace: `module:${padStart(m.idx, 5)}`,
        });
      } else {
        this.debug('eval-cache', `➕ %r is going to be initialized`, {
          namespace: `module:${padStart(getFileIdx(filename), 5)}`,
        });
        // Create the module if cached module is not available
        m = new Module(
          filename,
          this.options,
          this.cache,
          this.debuggerDepth + 1,
          this
        );
        m.transform = this.transform;

        // Store it in cache at this point with, otherwise
        // we would end up in infinite loop with cyclic dependencies
        this.cache.evalCache.set(filename, m);
      }

      const extension = path.extname(filename);
      if (extension === '.json' || this.extensions.includes(extension)) {
        let code: string | undefined;
        // Requested file can be already prepared for evaluation on the stage 1
        if (onlyList && this.cache.codeCache.has(filename)) {
          const cached = this.cache.codeCache.get(filename);
          const only = onlyList
            .split(',')
            .filter((token) => !m.#lazyValues.has(token));
          const cachedOnly = new Set(cached?.only ?? []);
          const isMatched =
            cachedOnly.has('*') ||
            (only && only.every((token) => cachedOnly.has(token)));
          if (cached && isMatched) {
            m.debug('code-cache', '✅');
            code = cached.result.code;
          } else {
            m.debug(
              'code-cache',
              '%o is missing (%o were cached)',
              only?.filter((token) => !cachedOnly.has(token)) ?? [],
              [...cachedOnly.values()]
            );
          }
        } else if (m.#isEvaluated) {
          m.debug(
            'code-cache',
            '✅ not in the code cache, but is already evaluated'
          );
        } else {
          // If code wasn't extracted from cache, read it from the file system
          // TODO: transpile the file
          m.debug(
            'code-cache',
            '❌ file has not been processed during prepare stage'
          );
          code = fs.readFileSync(filename, 'utf-8');
        }

        if (code) {
          if (/\.json$/.test(filename)) {
            // For JSON files, parse it to a JS object similar to Node
            m.exports = JSON.parse(code);
            m.#isEvaluated = true;
          } else {
            // For JS/TS files, evaluate the module
            m.evaluate(code);
          }
        }
      } else {
        // For non JS/JSON requires, just export the id
        // This is to support importing assets in webpack
        // The module will be resolved by css-loader
        m.exports = filename;
        m.#isEvaluated = true;
      }

      return m.exports;
    },
    {
      ensure: NOOP,
      resolve: this.resolve,
    }
  );

  evaluate(source: string): void {
    if (!source) {
      this.debug(`evaluate`, 'there is nothing to evaluate');
    }

    if (this.#isEvaluated) {
      this.debug('evaluate', `is already evaluated`);
      return;
    }

    this.debug('evaluate', `\n${source}`);

    this.#isEvaluated = true;

    const { filename } = this;

    const context = vm.createContext({
      clearImmediate: NOOP,
      clearInterval: NOOP,
      clearTimeout: NOOP,
      setImmediate: NOOP,
      setInterval: NOOP,
      setTimeout: NOOP,
      global,
      process,
      module: this,
      exports: this.#exports,
      require: this.require,
      __filename: filename,
      __dirname: path.dirname(filename),
    });

    try {
      const script = new vm.Script(
        `(function (exports) { ${source}\n})(exports);`,
        {
          filename,
        }
      );

      script.runInContext(context);
      return;
    } catch (e) {
      if (e instanceof EvalError) {
        this.debug('evaluate:error', '%O', e);

        throw e;
      }

      const callstack: string[] = ['', filename];
      let module = this.parentModule;
      while (module) {
        callstack.push(module.filename);
        module = module.parentModule;
      }

      this.debug('evaluate:error', '%O\n%O', e, callstack);
      throw new EvalError(
        `${(e as Error).message} in${callstack.join('\n| ')}\n`
      );
    }
  }
}

export default Module;