feat(std/node) add CommonJS require (#3380)

11 files changed, 1409 insertions, 0 deletions

diff --git a/std/node/require.ts b/std/node/require.ts
new file mode 100644
index 000000000..22393a418
--- /dev/null
+++ b/std/node/require.ts
@@ -0,0 +1,1189 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+import * as path from "../path/mod.ts";
+import { assert } from "../testing/asserts.ts";
+
+const CHAR_FORWARD_SLASH = "/".charCodeAt(0);
+const CHAR_BACKWARD_SLASH = "\\".charCodeAt(0);
+const CHAR_COLON = ":".charCodeAt(0);
+
+const isWindows = path.isWindows;
+
+const relativeResolveCache = Object.create(null);
+
+let requireDepth = 0;
+let statCache = null;
+
+type StatResult = -1 | 0 | 1;
+// Returns 0 if the path refers to
+// a file, 1 when it's a directory or < 0 on error.
+function stat(filename: string): StatResult {
+  filename = path.toNamespacedPath(filename);
+  if (statCache !== null) {
+    const result = statCache.get(filename);
+    if (result !== undefined) return result;
+  }
+  try {
+    const info = Deno.statSync(filename);
+    const result = info.isFile() ? 0 : 1;
+    if (statCache !== null) statCache.set(filename, result);
+    return result;
+  } catch (e) {
+    return -1;
+  }
+}
+
+function updateChildren(parent: Module, child: Module, scan: boolean): void {
+  const children = parent && parent.children;
+  if (children && !(scan && children.includes(child))) {
+    children.push(child);
+  }
+}
+
+class Module {
+  id: string;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  exports: any;
+  parent?: Module;
+  filename: string;
+  loaded: boolean;
+  children: Module[];
+  paths: string[];
+  path: string;
+  constructor(id = "", parent?: Module) {
+    this.id = id;
+    this.exports = {};
+    this.parent = parent;
+    updateChildren(parent, this, false);
+    this.filename = null;
+    this.loaded = false;
+    this.children = [];
+    this.paths = [];
+    this.path = path.dirname(id);
+  }
+  // TODO: populate this with polyfills!
+  static builtinModules: Module[] = [];
+  static _extensions: {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    [key: string]: (module: Module, filename: string) => any;
+  } = Object.create(null);
+  static _cache: { [key: string]: Module } = Object.create(null);
+  static _pathCache = Object.create(null);
+  static globalPaths: string[] = [];
+  // Proxy related code removed.
+  static wrapper = [
+    "(function (exports, require, module, __filename, __dirname) { ",
+    "\n});"
+  ];
+
+  // Loads a module at the given file path. Returns that module's
+  // `exports` property.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  require(id: string): any {
+    if (id === "") {
+      throw new Error(`id '${id}' must be a non-empty string`);
+    }
+    requireDepth++;
+    try {
+      return Module._load(id, this, /* isMain */ false);
+    } finally {
+      requireDepth--;
+    }
+  }
+
+  // Given a file name, pass it to the proper extension handler.
+  load(filename: string): void {
+    assert(!this.loaded);
+    this.filename = filename;
+    this.paths = Module._nodeModulePaths(path.dirname(filename));
+
+    const extension = findLongestRegisteredExtension(filename);
+    // Removed ESM code
+    Module._extensions[extension](this, filename);
+    this.loaded = true;
+    // Removed ESM code
+  }
+
+  // Run the file contents in the correct scope or sandbox. Expose
+  // the correct helper variables (require, module, exports) to
+  // the file.
+  // Returns exception, if any.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  _compile(content: string, filename: string): any {
+    // manifest code removed
+    const compiledWrapper = wrapSafe(filename, content);
+    // inspector code remove
+    const dirname = path.dirname(filename);
+    const require = makeRequireFunction(this);
+    const exports = this.exports;
+    const thisValue = exports;
+    if (requireDepth === 0) {
+      statCache = new Map();
+    }
+    const result = compiledWrapper.call(
+      thisValue,
+      exports,
+      require,
+      this,
+      filename,
+      dirname
+    );
+    if (requireDepth === 0) {
+      statCache = null;
+    }
+    return result;
+  }
+
+  static _resolveLookupPaths(
+    request: string,
+    parent: Module | null
+  ): string[] | null {
+    // Check for node modules paths.
+    if (
+      request.charAt(0) !== "." ||
+      (request.length > 1 &&
+        request.charAt(1) !== "." &&
+        request.charAt(1) !== "/" &&
+        (!isWindows || request.charAt(1) !== "\\"))
+    ) {
+      let paths = modulePaths;
+      if (parent !== null && parent.paths && parent.paths.length) {
+        paths = parent.paths.concat(paths);
+      }
+
+      return paths.length > 0 ? paths : null;
+    }
+
+    // With --eval, parent.id is not set and parent.filename is null.
+    if (!parent || !parent.id || !parent.filename) {
+      // Make require('./path/to/foo') work - normally the path is taken
+      // from realpath(__filename) but with eval there is no filename
+      const mainPaths = ["."].concat(Module._nodeModulePaths("."), modulePaths);
+      return mainPaths;
+    }
+
+    const parentDir = [path.dirname(parent.filename)];
+    return parentDir;
+  }
+
+  static _resolveFilename(
+    request: string,
+    parent: Module,
+    isMain: boolean,
+    options?: { paths: string[] }
+  ): string {
+    // Native module code removed
+    let paths: string[];
+
+    if (typeof options === "object" && options !== null) {
+      if (Array.isArray(options.paths)) {
+        const isRelative =
+          request.startsWith("./") ||
+          request.startsWith("../") ||
+          (isWindows && request.startsWith(".\\")) ||
+          request.startsWith("..\\");
+
+        if (isRelative) {
+          paths = options.paths;
+        } else {
+          const fakeParent = new Module("", null);
+
+          paths = [];
+
+          for (let i = 0; i < options.paths.length; i++) {
+            const path = options.paths[i];
+            fakeParent.paths = Module._nodeModulePaths(path);
+            const lookupPaths = Module._resolveLookupPaths(request, fakeParent);
+
+            for (let j = 0; j < lookupPaths.length; j++) {
+              if (!paths.includes(lookupPaths[j])) paths.push(lookupPaths[j]);
+            }
+          }
+        }
+      } else if (options.paths === undefined) {
+        paths = Module._resolveLookupPaths(request, parent);
+      } else {
+        throw new Error("options.paths is invalid");
+      }
+    } else {
+      paths = Module._resolveLookupPaths(request, parent);
+    }
+
+    // Look up the filename first, since that's the cache key.
+    const filename = Module._findPath(request, paths, isMain);
+    if (!filename) {
+      const requireStack = [];
+      for (let cursor = parent; cursor; cursor = cursor.parent) {
+        requireStack.push(cursor.filename || cursor.id);
+      }
+      let message = `Cannot find module '${request}'`;
+      if (requireStack.length > 0) {
+        message = message + "\nRequire stack:\n- " + requireStack.join("\n- ");
+      }
+      const err = new Error(message);
+      // @ts-ignore
+      err.code = "MODULE_NOT_FOUND";
+      // @ts-ignore
+      err.requireStack = requireStack;
+      throw err;
+    }
+    return filename as string;
+  }
+
+  static _findPath(
+    request: string,
+    paths: string[],
+    isMain: boolean
+  ): string | boolean {
+    const absoluteRequest = path.isAbsolute(request);
+    if (absoluteRequest) {
+      paths = [""];
+    } else if (!paths || paths.length === 0) {
+      return false;
+    }
+
+    const cacheKey =
+      request + "\x00" + (paths.length === 1 ? paths[0] : paths.join("\x00"));
+    const entry = Module._pathCache[cacheKey];
+    if (entry) {
+      return entry;
+    }
+
+    let exts;
+    let trailingSlash =
+      request.length > 0 &&
+      request.charCodeAt(request.length - 1) === CHAR_FORWARD_SLASH;
+    if (!trailingSlash) {
+      trailingSlash = /(?:^|\/)\.?\.$/.test(request);
+    }
+
+    // For each path
+    for (let i = 0; i < paths.length; i++) {
+      // Don't search further if path doesn't exist
+      const curPath = paths[i];
+
+      if (curPath && stat(curPath) < 1) continue;
+      const basePath = resolveExports(curPath, request, absoluteRequest);
+      let filename;
+
+      const rc = stat(basePath);
+      if (!trailingSlash) {
+        if (rc === 0) {
+          // File.
+          // preserveSymlinks removed
+          filename = toRealPath(basePath);
+        }
+
+        if (!filename) {
+          // Try it with each of the extensions
+          if (exts === undefined) exts = Object.keys(Module._extensions);
+          filename = tryExtensions(basePath, exts, isMain);
+        }
+      }
+
+      if (!filename && rc === 1) {
+        // Directory.
+        // try it with each of the extensions at "index"
+        if (exts === undefined) exts = Object.keys(Module._extensions);
+        filename = tryPackage(basePath, exts, isMain, request);
+      }
+
+      if (filename) {
+        Module._pathCache[cacheKey] = filename;
+        return filename;
+      }
+    }
+    // trySelf removed.
+
+    return false;
+  }
+
+  // Check the cache for the requested file.
+  // 1. If a module already exists in the cache: return its exports object.
+  // 2. If the module is native: call
+  //    `NativeModule.prototype.compileForPublicLoader()` and return the exports.
+  // 3. Otherwise, create a new module for the file and save it to the cache.
+  //    Then have it load  the file contents before returning its exports
+  //    object.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  static _load(request: string, parent: Module, isMain: boolean): any {
+    let relResolveCacheIdentifier;
+    if (parent) {
+      // Fast path for (lazy loaded) modules in the same directory. The indirect
+      // caching is required to allow cache invalidation without changing the old
+      // cache key names.
+      relResolveCacheIdentifier = `${parent.path}\x00${request}`;
+      const filename = relativeResolveCache[relResolveCacheIdentifier];
+      if (filename !== undefined) {
+        const cachedModule = Module._cache[filename];
+        if (cachedModule !== undefined) {
+          updateChildren(parent, cachedModule, true);
+          if (!cachedModule.loaded)
+            return getExportsForCircularRequire(cachedModule);
+          return cachedModule.exports;
+        }
+        delete relativeResolveCache[relResolveCacheIdentifier];
+      }
+    }
+
+    const filename = Module._resolveFilename(request, parent, isMain);
+
+    const cachedModule = Module._cache[filename];
+    if (cachedModule !== undefined) {
+      updateChildren(parent, cachedModule, true);
+      if (!cachedModule.loaded)
+        return getExportsForCircularRequire(cachedModule);
+      return cachedModule.exports;
+    }
+
+    // Native module NOT supported.
+
+    // Don't call updateChildren(), Module constructor already does.
+    const module = new Module(filename, parent);
+
+    if (isMain) {
+      // TODO: set process info
+      // process.mainModule = module;
+      module.id = ".";
+    }
+
+    Module._cache[filename] = module;
+    if (parent !== undefined) {
+      relativeResolveCache[relResolveCacheIdentifier] = filename;
+    }
+
+    let threw = true;
+    try {
+      // Source map code removed
+      module.load(filename);
+      threw = false;
+    } finally {
+      if (threw) {
+        delete Module._cache[filename];
+        if (parent !== undefined) {
+          delete relativeResolveCache[relResolveCacheIdentifier];
+        }
+      } else if (
+        module.exports &&
+        Object.getPrototypeOf(module.exports) ===
+          CircularRequirePrototypeWarningProxy
+      ) {
+        Object.setPrototypeOf(module.exports, PublicObjectPrototype);
+      }
+    }
+
+    return module.exports;
+  }
+
+  static wrap(script: string): string {
+    return `${Module.wrapper[0]}${script}${Module.wrapper[1]}`;
+  }
+
+  static _nodeModulePaths(from: string): string[] {
+    if (isWindows) {
+      // Guarantee that 'from' is absolute.
+      from = path.resolve(from);
+
+      // note: this approach *only* works when the path is guaranteed
+      // to be absolute.  Doing a fully-edge-case-correct path.split
+      // that works on both Windows and Posix is non-trivial.
+
+      // return root node_modules when path is 'D:\\'.
+      // path.resolve will make sure from.length >=3 in Windows.
+      if (
+        from.charCodeAt(from.length - 1) === CHAR_BACKWARD_SLASH &&
+        from.charCodeAt(from.length - 2) === CHAR_COLON
+      )
+        return [from + "node_modules"];
+
+      const paths = [];
+      for (let i = from.length - 1, p = 0, last = from.length; i >= 0; --i) {
+        const code = from.charCodeAt(i);
+        // The path segment separator check ('\' and '/') was used to get
+        // node_modules path for every path segment.
+        // Use colon as an extra condition since we can get node_modules
+        // path for drive root like 'C:\node_modules' and don't need to
+        // parse drive name.
+        if (
+          code === CHAR_BACKWARD_SLASH ||
+          code === CHAR_FORWARD_SLASH ||
+          code === CHAR_COLON
+        ) {
+          if (p !== nmLen) paths.push(from.slice(0, last) + "\\node_modules");
+          last = i;
+          p = 0;
+        } else if (p !== -1) {
+          if (nmChars[p] === code) {
+            ++p;
+          } else {
+            p = -1;
+          }
+        }
+      }
+
+      return paths;
+    } else {
+      // posix
+      // Guarantee that 'from' is absolute.
+      from = path.resolve(from);
+      // Return early not only to avoid unnecessary work, but to *avoid* returning
+      // an array of two items for a root: [ '//node_modules', '/node_modules' ]
+      if (from === "/") return ["/node_modules"];
+
+      // note: this approach *only* works when the path is guaranteed
+      // to be absolute.  Doing a fully-edge-case-correct path.split
+      // that works on both Windows and Posix is non-trivial.
+      const paths = [];
+      for (let i = from.length - 1, p = 0, last = from.length; i >= 0; --i) {
+        const code = from.charCodeAt(i);
+        if (code === CHAR_FORWARD_SLASH) {
+          if (p !== nmLen) paths.push(from.slice(0, last) + "/node_modules");
+          last = i;
+          p = 0;
+        } else if (p !== -1) {
+          if (nmChars[p] === code) {
+            ++p;
+          } else {
+            p = -1;
+          }
+        }
+      }
+
+      // Append /node_modules to handle root paths.
+      paths.push("/node_modules");
+
+      return paths;
+    }
+  }
+
+  static createRequire(filename: string | URL): RequireFunction {
+    let filepath: string;
+    if (
+      filename instanceof URL ||
+      (typeof filename === "string" && !path.isAbsolute(filename))
+    ) {
+      filepath = fileURLToPath(filename);
+    } else if (typeof filename !== "string") {
+      throw new Error("filename should be a string");
+    } else {
+      filepath = filename;
+    }
+    return createRequireFromPath(filepath);
+  }
+
+  static _initPaths(): void {
+    const homeDir = Deno.env("HOME");
+    const nodePath = Deno.env("NODE_PATH");
+
+    // Removed $PREFIX/bin/node case
+
+    let paths = [];
+
+    if (homeDir) {
+      paths.unshift(path.resolve(homeDir, ".node_libraries"));
+      paths.unshift(path.resolve(homeDir, ".node_modules"));
+    }
+
+    if (nodePath) {
+      paths = nodePath
+        .split(path.delimiter)
+        .filter(function pathsFilterCB(path) {
+          return !!path;
+        })
+        .concat(paths);
+    }
+
+    modulePaths = paths;
+
+    // Clone as a shallow copy, for introspection.
+    Module.globalPaths = modulePaths.slice(0);
+  }
+
+  static _preloadModules(requests: string[]): void {
+    if (!Array.isArray(requests)) {
+      return;
+    }
+
+    // Preloaded modules have a dummy parent module which is deemed to exist
+    // in the current working directory. This seeds the search path for
+    // preloaded modules.
+    const parent = new Module("internal/preload", null);
+    try {
+      parent.paths = Module._nodeModulePaths(Deno.cwd());
+    } catch (e) {
+      if (e.code !== "ENOENT") {
+        throw e;
+      }
+    }
+    for (let n = 0; n < requests.length; n++) {
+      parent.require(requests[n]);
+    }
+  }
+}
+
+let modulePaths = [];
+
+// Given a module name, and a list of paths to test, returns the first
+// matching file in the following precedence.
+//
+// require("a.<ext>")
+//   -> a.<ext>
+//
+// require("a")
+//   -> a
+//   -> a.<ext>
+//   -> a/index.<ext>
+
+const packageJsonCache = new Map<string, PackageInfo | null>();
+
+interface PackageInfo {
+  name?: string;
+  main?: string;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  exports?: any;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  type?: any;
+}
+
+function readPackage(requestPath: string): PackageInfo | null {
+  const jsonPath = path.resolve(requestPath, "package.json");
+
+  const existing = packageJsonCache.get(jsonPath);
+  if (existing !== undefined) {
+    return existing;
+  }
+
+  let json: string | undefined;
+  try {
+    json = new TextDecoder().decode(
+      Deno.readFileSync(path.toNamespacedPath(jsonPath))
+    );
+  } catch {}
+
+  if (json === undefined) {
+    packageJsonCache.set(jsonPath, null);
+    return null;
+  }
+
+  try {
+    const parsed = JSON.parse(json);
+    const filtered = {
+      name: parsed.name,
+      main: parsed.main,
+      exports: parsed.exports,
+      type: parsed.type
+    };
+    packageJsonCache.set(jsonPath, filtered);
+    return filtered;
+  } catch (e) {
+    e.path = jsonPath;
+    e.message = "Error parsing " + jsonPath + ": " + e.message;
+    throw e;
+  }
+}
+
+function readPackageScope(
+  checkPath
+): { path: string; data: PackageInfo } | false {
+  const rootSeparatorIndex = checkPath.indexOf(path.sep);
+  let separatorIndex;
+  while (
+    (separatorIndex = checkPath.lastIndexOf(path.sep)) > rootSeparatorIndex
+  ) {
+    checkPath = checkPath.slice(0, separatorIndex);
+    if (checkPath.endsWith(path.sep + "node_modules")) return false;
+    const pjson = readPackage(checkPath);
+    if (pjson)
+      return {
+        path: checkPath,
+        data: pjson
+      };
+  }
+  return false;
+}
+
+function readPackageMain(requestPath: string): string | undefined {
+  const pkg = readPackage(requestPath);
+  return pkg ? pkg.main : undefined;
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function readPackageExports(requestPath: string): any | undefined {
+  const pkg = readPackage(requestPath);
+  return pkg ? pkg.exports : undefined;
+}
+
+function tryPackage(
+  requestPath: string,
+  exts: string[],
+  isMain: boolean,
+  _originalPath: string
+): string | false {
+  const pkg = readPackageMain(requestPath);
+
+  if (!pkg) {
+    return tryExtensions(path.resolve(requestPath, "index"), exts, isMain);
+  }
+
+  const filename = path.resolve(requestPath, pkg);
+  let actual =
+    tryFile(filename, isMain) ||
+    tryExtensions(filename, exts, isMain) ||
+    tryExtensions(path.resolve(filename, "index"), exts, isMain);
+  if (actual === false) {
+    actual = tryExtensions(path.resolve(requestPath, "index"), exts, isMain);
+    if (!actual) {
+      // eslint-disable-next-line no-restricted-syntax
+      const err = new Error(
+        `Cannot find module '${filename}'. ` +
+          'Please verify that the package.json has a valid "main" entry'
+      );
+      // @ts-ignore
+      err.code = "MODULE_NOT_FOUND";
+      throw err;
+    }
+  }
+  return actual;
+}
+
+// Check if the file exists and is not a directory
+// if using --preserve-symlinks and isMain is false,
+// keep symlinks intact, otherwise resolve to the
+// absolute realpath.
+function tryFile(requestPath: string, _isMain: boolean): string | false {
+  const rc = stat(requestPath);
+  return rc === 0 && toRealPath(requestPath);
+}
+
+function toRealPath(requestPath: string): string {
+  // Deno does not have realpath implemented yet.
+  let fullPath = requestPath;
+  while (true) {
+    try {
+      fullPath = Deno.readlinkSync(fullPath);
+    } catch {
+      break;
+    }
+  }
+  return path.resolve(requestPath);
+}
+
+// Given a path, check if the file exists with any of the set extensions
+function tryExtensions(
+  p: string,
+  exts: string[],
+  isMain: boolean
+): string | false {
+  for (let i = 0; i < exts.length; i++) {
+    const filename = tryFile(p + exts[i], isMain);
+
+    if (filename) {
+      return filename;
+    }
+  }
+  return false;
+}
+
+// Find the longest (possibly multi-dot) extension registered in
+// Module._extensions
+function findLongestRegisteredExtension(filename: string): string {
+  const name = path.basename(filename);
+  let currentExtension;
+  let index;
+  let startIndex = 0;
+  while ((index = name.indexOf(".", startIndex)) !== -1) {
+    startIndex = index + 1;
+    if (index === 0) continue; // Skip dotfiles like .gitignore
+    currentExtension = name.slice(index);
+    if (Module._extensions[currentExtension]) return currentExtension;
+  }
+  return ".js";
+}
+
+// --experimental-resolve-self trySelf() support removed.
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function isConditionalDotExportSugar(exports: any, _basePath: string): boolean {
+  if (typeof exports === "string") return true;
+  if (Array.isArray(exports)) return true;
+  if (typeof exports !== "object") return false;
+  let isConditional = false;
+  let firstCheck = true;
+  for (const key of Object.keys(exports)) {
+    const curIsConditional = key[0] !== ".";
+    if (firstCheck) {
+      firstCheck = false;
+      isConditional = curIsConditional;
+    } else if (isConditional !== curIsConditional) {
+      throw new Error(
+        '"exports" cannot ' +
+          "contain some keys starting with '.' and some not. The exports " +
+          "object must either be an object of package subpath keys or an " +
+          "object of main entry condition name keys only."
+      );
+    }
+  }
+  return isConditional;
+}
+
+function applyExports(basePath: string, expansion: string): string {
+  const mappingKey = `.${expansion}`;
+
+  let pkgExports = readPackageExports(basePath);
+  if (pkgExports === undefined || pkgExports === null)
+    return path.resolve(basePath, mappingKey);
+
+  if (isConditionalDotExportSugar(pkgExports, basePath))
+    pkgExports = { ".": pkgExports };
+
+  if (typeof pkgExports === "object") {
+    if (pkgExports.hasOwnProperty(mappingKey)) {
+      const mapping = pkgExports[mappingKey];
+      return resolveExportsTarget(
+        pathToFileURL(basePath + "/"),
+        mapping,
+        "",
+        basePath,
+        mappingKey
+      );
+    }
+
+    // Fallback to CJS main lookup when no main export is defined
+    if (mappingKey === ".") return basePath;
+
+    let dirMatch = "";
+    for (const candidateKey of Object.keys(pkgExports)) {
+      if (candidateKey[candidateKey.length - 1] !== "/") continue;
+      if (
+        candidateKey.length > dirMatch.length &&
+        mappingKey.startsWith(candidateKey)
+      ) {
+        dirMatch = candidateKey;
+      }
+    }
+
+    if (dirMatch !== "") {
+      const mapping = pkgExports[dirMatch];
+      const subpath = mappingKey.slice(dirMatch.length);
+      return resolveExportsTarget(
+        pathToFileURL(basePath + "/"),
+        mapping,
+        subpath,
+        basePath,
+        mappingKey
+      );
+    }
+  }
+  // Fallback to CJS main lookup when no main export is defined
+  if (mappingKey === ".") return basePath;
+
+  const e = new Error(
+    `Package exports for '${basePath}' do not define ` +
+      `a '${mappingKey}' subpath`
+  );
+  // @ts-ignore
+  e.code = "MODULE_NOT_FOUND";
+  throw e;
+}
+
+// This only applies to requests of a specific form:
+// 1. name/.*
+// 2. @scope/name/.*
+const EXPORTS_PATTERN = /^((?:@[^/\\%]+\/)?[^./\\%][^/\\%]*)(\/.*)?$/;
+function resolveExports(
+  nmPath: string,
+  request: string,
+  absoluteRequest: boolean
+): string {
+  // The implementation's behavior is meant to mirror resolution in ESM.
+  if (!absoluteRequest) {
+    const [, name, expansion = ""] = request.match(EXPORTS_PATTERN) || [];
+    if (!name) {
+      return path.resolve(nmPath, request);
+    }
+
+    const basePath = path.resolve(nmPath, name);
+    return applyExports(basePath, expansion);
+  }
+
+  return path.resolve(nmPath, request);
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function resolveExportsTarget(
+  pkgPath: URL,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  target: any,
+  subpath: string,
+  basePath: string,
+  mappingKey: string
+): string {
+  if (typeof target === "string") {
+    if (
+      target.startsWith("./") &&
+      (subpath.length === 0 || target.endsWith("/"))
+    ) {
+      const resolvedTarget = new URL(target, pkgPath);
+      const pkgPathPath = pkgPath.pathname;
+      const resolvedTargetPath = resolvedTarget.pathname;
+      if (
+        resolvedTargetPath.startsWith(pkgPathPath) &&
+        resolvedTargetPath.indexOf("/node_modules/", pkgPathPath.length - 1) ===
+          -1
+      ) {
+        const resolved = new URL(subpath, resolvedTarget);
+        const resolvedPath = resolved.pathname;
+        if (
+          resolvedPath.startsWith(resolvedTargetPath) &&
+          resolvedPath.indexOf("/node_modules/", pkgPathPath.length - 1) === -1
+        ) {
+          return fileURLToPath(resolved);
+        }
+      }
+    }
+  } else if (Array.isArray(target)) {
+    for (const targetValue of target) {
+      if (Array.isArray(targetValue)) continue;
+      try {
+        return resolveExportsTarget(
+          pkgPath,
+          targetValue,
+          subpath,
+          basePath,
+          mappingKey
+        );
+      } catch (e) {
+        if (e.code !== "MODULE_NOT_FOUND") throw e;
+      }
+    }
+  } else if (typeof target === "object" && target !== null) {
+    // removed experimentalConditionalExports
+    if (target.hasOwnProperty("default")) {
+      try {
+        return resolveExportsTarget(
+          pkgPath,
+          target.default,
+          subpath,
+          basePath,
+          mappingKey
+        );
+      } catch (e) {
+        if (e.code !== "MODULE_NOT_FOUND") throw e;
+      }
+    }
+  }
+  let e: Error;
+  if (mappingKey !== ".") {
+    e = new Error(
+      `Package exports for '${basePath}' do not define a ` +
+        `valid '${mappingKey}' target${subpath ? " for " + subpath : ""}`
+    );
+  } else {
+    e = new Error(`No valid exports main found for '${basePath}'`);
+  }
+  // @ts-ignore
+  e.code = "MODULE_NOT_FOUND";
+  throw e;
+}
+
+// 'node_modules' character codes reversed
+const nmChars = [115, 101, 108, 117, 100, 111, 109, 95, 101, 100, 111, 110];
+const nmLen = nmChars.length;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function emitCircularRequireWarning(prop: any): void {
+  console.error(
+    `Accessing non-existent property '${String(
+      prop
+    )}' of module exports inside circular dependency`
+  );
+}
+
+// A Proxy that can be used as the prototype of a module.exports object and
+// warns when non-existend properties are accessed.
+const CircularRequirePrototypeWarningProxy = new Proxy(
+  {},
+  {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    get(target, prop): any {
+      if (prop in target) return target[prop];
+      emitCircularRequireWarning(prop);
+      return undefined;
+    },
+
+    getOwnPropertyDescriptor(target, prop): PropertyDescriptor | undefined {
+      if (target.hasOwnProperty(prop))
+        return Object.getOwnPropertyDescriptor(target, prop);
+      emitCircularRequireWarning(prop);
+      return undefined;
+    }
+  }
+);
+
+// Object.prototype and ObjectProtoype refer to our 'primordials' versions
+// and are not identical to the versions on the global object.
+const PublicObjectPrototype = window.Object.prototype;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function getExportsForCircularRequire(module: Module): any {
+  if (
+    module.exports &&
+    Object.getPrototypeOf(module.exports) === PublicObjectPrototype &&
+    // Exclude transpiled ES6 modules / TypeScript code because those may
+    // employ unusual patterns for accessing 'module.exports'. That should be
+    // okay because ES6 modules have a different approach to circular
+    // dependencies anyway.
+    !module.exports.__esModule
+  ) {
+    // This is later unset once the module is done loading.
+    Object.setPrototypeOf(module.exports, CircularRequirePrototypeWarningProxy);
+  }
+
+  return module.exports;
+}
+
+type RequireWrapper = (
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  exports: any,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  require: any,
+  module: Module,
+  __filename: string,
+  __dirname: string
+) => void;
+
+function wrapSafe(filename_: string, content: string): RequireWrapper {
+  // TODO: fix this
+  const wrapper = Module.wrap(content);
+  // @ts-ignore
+  const [f, err] = Deno.core.evalContext(wrapper);
+  if (err) {
+    throw err;
+  }
+  return f;
+  // ESM code removed.
+}
+
+// Native extension for .js
+Module._extensions[".js"] = (module: Module, filename: string): void => {
+  if (filename.endsWith(".js")) {
+    const pkg = readPackageScope(filename);
+    if (pkg !== false && pkg.data && pkg.data.type === "module") {
+      throw new Error("Importing ESM module");
+    }
+  }
+  const content = new TextDecoder().decode(Deno.readFileSync(filename));
+  module._compile(content, filename);
+};
+
+// Native extension for .json
+Module._extensions[".json"] = (module: Module, filename: string): void => {
+  const content = new TextDecoder().decode(Deno.readFileSync(filename));
+  // manifest code removed
+  try {
+    module.exports = JSON.parse(stripBOM(content));
+  } catch (err) {
+    err.message = filename + ": " + err.message;
+    throw err;
+  }
+};
+
+// .node extension is not supported
+
+function createRequireFromPath(filename: string): RequireFunction {
+  // Allow a directory to be passed as the filename
+  const trailingSlash =
+    filename.endsWith("/") || (isWindows && filename.endsWith("\\"));
+
+  const proxyPath = trailingSlash ? path.join(filename, "noop.js") : filename;
+
+  const m = new Module(proxyPath);
+  m.filename = proxyPath;
+
+  m.paths = Module._nodeModulePaths(m.path);
+  return makeRequireFunction(m);
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type Require = (id: string) => any;
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type RequireResolve = (request: string, options: any) => string;
+interface RequireResolveFunction extends RequireResolve {
+  paths: (request: string) => string[] | null;
+}
+
+interface RequireFunction extends Require {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  resolve: RequireResolveFunction;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  extensions: { [key: string]: (module: Module, filename: string) => any };
+  cache: { [key: string]: Module };
+}
+
+function makeRequireFunction(mod: Module): RequireFunction {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const require = function require(path: string): any {
+    return mod.require(path);
+  };
+
+  function resolve(request: string, options?: { paths: string[] }): string {
+    return Module._resolveFilename(request, mod, false, options);
+  }
+
+  require.resolve = resolve;
+
+  function paths(request: string): string[] | null {
+    return Module._resolveLookupPaths(request, mod);
+  }
+
+  resolve.paths = paths;
+  // TODO: set main
+  // require.main = process.mainModule;
+
+  // Enable support to add extra extension types.
+  require.extensions = Module._extensions;
+
+  require.cache = Module._cache;
+
+  return require;
+}
+
+/**
+ * Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
+ * because the buffer-to-string conversion in `fs.readFileSync()`
+ * translates it to FEFF, the UTF-16 BOM.
+ */
+function stripBOM(content: string): string {
+  if (content.charCodeAt(0) === 0xfeff) {
+    content = content.slice(1);
+  }
+  return content;
+}
+
+const forwardSlashRegEx = /\//g;
+const CHAR_LOWERCASE_A = "a".charCodeAt(0);
+const CHAR_LOWERCASE_Z = "z".charCodeAt(0);
+
+function getPathFromURLWin32(url: URL): string {
+  // const hostname = url.hostname;
+  let pathname = url.pathname;
+  for (let n = 0; n < pathname.length; n++) {
+    if (pathname[n] === "%") {
+      const third = pathname.codePointAt(n + 2) | 0x20;
+      if (
+        (pathname[n + 1] === "2" && third === 102) || // 2f 2F /
+        (pathname[n + 1] === "5" && third === 99)
+      ) {
+        // 5c 5C \
+        throw new Error(
+          "Invalid file url path: must not include encoded \\ or / characters"
+        );
+      }
+    }
+  }
+  pathname = pathname.replace(forwardSlashRegEx, "\\");
+  pathname = decodeURIComponent(pathname);
+  // TODO: handle windows hostname case (needs bindings)
+  const letter = pathname.codePointAt(1) | 0x20;
+  const sep = pathname[2];
+  if (
+    letter < CHAR_LOWERCASE_A ||
+    letter > CHAR_LOWERCASE_Z || // a..z A..Z
+    sep !== ":"
+  ) {
+    throw new Error("Invalid file URL path: must be absolute");
+  }
+  return pathname.slice(1);
+}
+
+function getPathFromURLPosix(url: URL): string {
+  if (url.hostname !== "") {
+    throw new Error("Invalid file URL host");
+  }
+  const pathname = url.pathname;
+  for (let n = 0; n < pathname.length; n++) {
+    if (pathname[n] === "%") {
+      const third = pathname.codePointAt(n + 2) | 0x20;
+      if (pathname[n + 1] === "2" && third === 102) {
+        throw new Error(
+          "Invalid file URL path: must not include encoded / characters"
+        );
+      }
+    }
+  }
+  return decodeURIComponent(pathname);
+}
+
+function fileURLToPath(path: string | URL): string {
+  if (typeof path === "string") {
+    path = new URL(path);
+  }
+  if (path.protocol !== "file:") {
+    throw new Error("Protocol has to be file://");
+  }
+  return isWindows ? getPathFromURLWin32(path) : getPathFromURLPosix(path);
+}
+
+const percentRegEx = /%/g;
+const backslashRegEx = /\\/g;
+const newlineRegEx = /\n/g;
+const carriageReturnRegEx = /\r/g;
+const tabRegEx = /\t/g;
+function pathToFileURL(filepath: string): URL {
+  let resolved = path.resolve(filepath);
+  // path.resolve strips trailing slashes so we must add them back
+  const filePathLast = filepath.charCodeAt(filepath.length - 1);
+  if (
+    (filePathLast === CHAR_FORWARD_SLASH ||
+      (isWindows && filePathLast === CHAR_BACKWARD_SLASH)) &&
+    resolved[resolved.length - 1] !== path.sep
+  )
+    resolved += "/";
+  const outURL = new URL("file://");
+  if (resolved.includes("%")) resolved = resolved.replace(percentRegEx, "%25");
+  // In posix, "/" is a valid character in paths
+  if (!isWindows && resolved.includes("\\"))
+    resolved = resolved.replace(backslashRegEx, "%5C");
+  if (resolved.includes("\n")) resolved = resolved.replace(newlineRegEx, "%0A");
+  if (resolved.includes("\r"))
+    resolved = resolved.replace(carriageReturnRegEx, "%0D");
+  if (resolved.includes("\t")) resolved = resolved.replace(tabRegEx, "%09");
+  outURL.pathname = resolved;
+  return outURL;
+}
+
+/**
+ * Create a `require` function that can be used to import CJS modules
+ * @param path path of this module
+ */
+function makeRequire(filePath: string): RequireFunction {
+  let mod: Module;
+  const fullPath = path.resolve(filePath);
+  if (fullPath in Module._cache) {
+    mod = Module._cache[fullPath];
+  } else {
+    mod = new Module(fullPath);
+  }
+  return makeRequireFunction(mod);
+}
+
+export { makeRequire };
diff --git a/std/node/require_test.ts b/std/node/require_test.ts
new file mode 100644
index 000000000..7cac6d6b2
--- /dev/null
+++ b/std/node/require_test.ts
@@ -0,0 +1,27 @@
+import { test } from "../testing/mod.ts";
+import { assertEquals, assert } from "../testing/asserts.ts";
+import { makeRequire } from "./require.ts";
+
+const selfPath = window.unescape(import.meta.url.substring(7));
+// TS compiler would try to resolve if function named "require"
+// Thus suffixing it with require_ to fix this...
+const require_ = makeRequire(selfPath);
+
+test(function requireSuccess() {
+  const result = require_("./node/tests/cjs/cjs_a.js");
+  assert("helloA" in result);
+  assert("helloB" in result);
+  assert("C" in result);
+  assert("leftPad" in result);
+  assertEquals(result.helloA(), "A");
+  assertEquals(result.helloB(), "B");
+  assertEquals(result.C, "C");
+  assertEquals(result.leftPad("pad", 4), " pad");
+});
+
+test(function requireCycle() {
+  const resultA = require_("./node/tests/cjs/cjs_cycle_a");
+  const resultB = require_("./node/tests/cjs/cjs_cycle_b");
+  assert(resultA);
+  assert(resultB);
+});
diff --git a/std/node/tests/cjs/cjs_a.js b/std/node/tests/cjs/cjs_a.js
new file mode 100644
index 000000000..b8f69c857
--- /dev/null
+++ b/std/node/tests/cjs/cjs_a.js
@@ -0,0 +1,10 @@
+/* eslint-disable */
+const { helloB } = require("./cjs_b.js");
+const C = require("./subdir/cjs_c");
+const leftPad = require("left-pad");
+
+function helloA() {
+  return "A";
+}
+
+module.exports = { helloA, helloB, C, leftPad };
diff --git a/std/node/tests/cjs/cjs_b.js b/std/node/tests/cjs/cjs_b.js
new file mode 100644
index 000000000..17499012c
--- /dev/null
+++ b/std/node/tests/cjs/cjs_b.js
@@ -0,0 +1,5 @@
+function helloB() {
+  return "B";
+}
+
+module.exports = { helloB };
diff --git a/std/node/tests/cjs/cjs_cycle_a.js b/std/node/tests/cjs/cjs_cycle_a.js
new file mode 100644
index 000000000..7a4e5a5f6
--- /dev/null
+++ b/std/node/tests/cjs/cjs_cycle_a.js
@@ -0,0 +1,3 @@
+module.exports = false;
+require("./cjs_cycle_a");
+module.exports = true;
diff --git a/std/node/tests/cjs/cjs_cycle_b.js b/std/node/tests/cjs/cjs_cycle_b.js
new file mode 100644
index 000000000..d85a1fc84
--- /dev/null
+++ b/std/node/tests/cjs/cjs_cycle_b.js
@@ -0,0 +1,3 @@
+module.exports = false;
+require("./cjs_cycle_b");
+module.exports = true;
diff --git a/std/node/tests/cjs/subdir/cjs_c.js b/std/node/tests/cjs/subdir/cjs_c.js
new file mode 100644
index 000000000..4e7d7ebe5
--- /dev/null
+++ b/std/node/tests/cjs/subdir/cjs_c.js
@@ -0,0 +1 @@
+module.exports = "C";
diff --git a/std/node/tests/node_modules/left-pad/README.md b/std/node/tests/node_modules/left-pad/README.md
new file mode 100644
index 000000000..e86ca7cc5
--- /dev/null
+++ b/std/node/tests/node_modules/left-pad/README.md
@@ -0,0 +1,36 @@
+## left-pad
+
+String left pad
+
+[![Build Status][travis-image]][travis-url]
+
+## Install
+
+```bash
+$ npm install left-pad
+```
+
+## Usage
+
+```js
+const leftPad = require('left-pad')
+
+leftPad('foo', 5)
+// => "  foo"
+
+leftPad('foobar', 6)
+// => "foobar"
+
+leftPad(1, 2, '0')
+// => "01"
+
+leftPad(17, 5, 0)
+// => "00017"
+```
+
+**NOTE:** The third argument should be a single `char`. However the module doesn't throw an error if you supply more than one `char`s. See [#28](https://github.com/stevemao/left-pad/pull/28).
+
+**NOTE:** Characters having code points outside of [BMP plan](https://en.wikipedia.org/wiki/Plane_(Unicode)#Basic_Multilingual_Plane) are considered a two distinct characters. See [#58](https://github.com/stevemao/left-pad/issues/58).
+
+[travis-image]: https://travis-ci.org/stevemao/left-pad.svg?branch=master
+[travis-url]: https://travis-ci.org/stevemao/left-pad
diff --git a/std/node/tests/node_modules/left-pad/index.js b/std/node/tests/node_modules/left-pad/index.js
new file mode 100644
index 000000000..e90aec35d
--- /dev/null
+++ b/std/node/tests/node_modules/left-pad/index.js
@@ -0,0 +1,52 @@
+/* This program is free software. It comes without any warranty, to
+     * the extent permitted by applicable law. You can redistribute it
+     * and/or modify it under the terms of the Do What The Fuck You Want
+     * To Public License, Version 2, as published by Sam Hocevar. See
+     * http://www.wtfpl.net/ for more details. */
+'use strict';
+module.exports = leftPad;
+
+var cache = [
+  '',
+  ' ',
+  '  ',
+  '   ',
+  '    ',
+  '     ',
+  '      ',
+  '       ',
+  '        ',
+  '         '
+];
+
+function leftPad (str, len, ch) {
+  // convert `str` to a `string`
+  str = str + '';
+  // `len` is the `pad`'s length now
+  len = len - str.length;
+  // doesn't need to pad
+  if (len <= 0) return str;
+  // `ch` defaults to `' '`
+  if (!ch && ch !== 0) ch = ' ';
+  // convert `ch` to a `string` cuz it could be a number
+  ch = ch + '';
+  // cache common use cases
+  if (ch === ' ' && len < 10) return cache[len] + str;
+  // `pad` starts with an empty string
+  var pad = '';
+  // loop
+  while (true) {
+    // add `ch` to `pad` if `len` is odd
+    if (len & 1) pad += ch;
+    // divide `len` by 2, ditch the remainder
+    len >>= 1;
+    // "double" the `ch` so this operation count grows logarithmically on `len`
+    // each time `ch` is "doubled", the `len` would need to be "doubled" too
+    // similar to finding a value in binary search tree, hence O(log(n))
+    if (len) ch += ch;
+    // `len` is 0, exit the loop
+    else break;
+  }
+  // pad `str`!
+  return pad + str;
+}
diff --git a/std/node/tests/node_modules/left-pad/package.json b/std/node/tests/node_modules/left-pad/package.json
new file mode 100644
index 000000000..57be04271
--- /dev/null
+++ b/std/node/tests/node_modules/left-pad/package.json
@@ -0,0 +1,68 @@
+{
+  "_from": "left-pad",
+  "_id": "left-pad@1.3.0",
+  "_inBundle": false,
+  "_integrity": "sha512-XI5MPzVNApjAyhQzphX8BkmKsKUxD4LdyK24iZeQGinBN9yTQT3bFlCBy/aVx2HrNcqQGsdot8ghrjyrvMCoEA==",
+  "_location": "/left-pad",
+  "_phantomChildren": {},
+  "_requested": {
+    "type": "tag",
+    "registry": true,
+    "raw": "left-pad",
+    "name": "left-pad",
+    "escapedName": "left-pad",
+    "rawSpec": "",
+    "saveSpec": null,
+    "fetchSpec": "latest"
+  },
+  "_requiredBy": [
+    "#USER",
+    "/"
+  ],
+  "_resolved": "https://registry.npmjs.org/left-pad/-/left-pad-1.3.0.tgz",
+  "_shasum": "5b8a3a7765dfe001261dde915589e782f8c94d1e",
+  "_spec": "left-pad",
+  "_where": "/Users/kun/Projects/Deno/deno/std/node/tests",
+  "author": {
+    "name": "azer"
+  },
+  "bugs": {
+    "url": "https://github.com/stevemao/left-pad/issues"
+  },
+  "bundleDependencies": false,
+  "deprecated": "use String.prototype.padStart()",
+  "description": "String left pad",
+  "devDependencies": {
+    "benchmark": "^2.1.0",
+    "fast-check": "0.0.8",
+    "tape": "*"
+  },
+  "homepage": "https://github.com/stevemao/left-pad#readme",
+  "keywords": [
+    "leftpad",
+    "left",
+    "pad",
+    "padding",
+    "string",
+    "repeat"
+  ],
+  "license": "WTFPL",
+  "main": "index.js",
+  "maintainers": [
+    {
+      "name": "Cameron Westland",
+      "email": "camwest@gmail.com"
+    }
+  ],
+  "name": "left-pad",
+  "repository": {
+    "url": "git+ssh://git@github.com/stevemao/left-pad.git",
+    "type": "git"
+  },
+  "scripts": {
+    "bench": "node perf/perf.js",
+    "test": "node test"
+  },
+  "types": "index.d.ts",
+  "version": "1.3.0"
+}
diff --git a/std/node/tests/package.json b/std/node/tests/package.json
new file mode 100644
index 000000000..08c54d588
--- /dev/null
+++ b/std/node/tests/package.json
@@ -0,0 +1,15 @@
+{
+  "name": "deno_std_node",
+  "version": "0.0.1",
+  "description": "",
+  "main": "index.js",
+  "dependencies": {
+    "left-pad": "^1.3.0"
+  },
+  "devDependencies": {},
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC"
+}