Add support for Node.js v16.3.0+

lib/binding.js

@@ -6,7 +6,7 @@ const File = require('./file');
 const FileDescriptor = require('./descriptor');
 const Directory = require('./directory');
 const SymbolicLink = require('./symlink');
-const FSError = require('./error');
+const {FSError} = require('./error');
 const constants = require('constants');
 const getPathParts = require('./filesystem').getPathParts;
 

lib/error.js

@@ -41,6 +41,21 @@ FSError.prototype = new Error();
 FSError.codes = codes;
 
 /**
- * Error constructor.
+ * Create an abort error for when an asynchronous task was aborted.
+ * @constructor
+ */
+function AbortError() {
+  Error.call(this);
+  this.code = 'ABORT_ERR';
+  this.name = 'AbortError';
+  Error.captureStackTrace(this, AbortError);
+}
+
+/**
+ * FSError constructor.
+ */
+exports.FSError = FSError;
+/**
+ * AbortError constructor.
  */
-exports = module.exports = FSError;
+exports.AbortError = AbortError;

lib/filesystem.js

@@ -5,7 +5,7 @@ const path = require('path');
 
 const Directory = require('./directory');
 const File = require('./file');
-const FSError = require('./error');
+const {FSError} = require('./error');
 const SymbolicLink = require('./symlink');
 
 const isWindows = process.platform === 'win32';

lib/index.js

@@ -1,12 +1,16 @@
 'use strict';
 
 const Binding = require('./binding');
-const FSError = require('./error');
+const {FSError} = require('./error');
 const FileSystem = require('./filesystem');
 const realBinding = process.binding('fs');
 const path = require('path');
 const loader = require('./loader');
 const bypass = require('./bypass');
+const {
+  getReadFileContextPrototype,
+  patchReadFileContext
+} = require('./readfilecontext');
 const fs = require('fs');
 
 const toNamespacedPath = FileSystem.toNamespacedPath;
@@ -50,6 +54,10 @@ for (const key in Binding.prototype) {
   }
 }
 
+const readFileContextPrototype = getReadFileContextPrototype();
+
+patchReadFileContext(readFileContextPrototype);
+
 function overrideBinding(binding) {
   realBinding._mockedBinding = binding;
 }
@@ -94,6 +102,10 @@ function overrideCreateWriteStream() {
   };
 }
 
+function overrideReadFileContext(binding) {
+  readFileContextPrototype._mockedBinding = binding;
+}
+
 function restoreBinding() {
   delete realBinding._mockedBinding;
   realBinding.Stats = realStats;
@@ -110,6 +122,10 @@ function restoreCreateWriteStream() {
   fs.createWriteStream = realCreateWriteStream;
 }
 
+function restoreReadFileContext(binding) {
+  delete readFileContextPrototype._mockedBinding;
+}
+
 /**
  * Swap out the fs bindings for a mock file system.
  * @param {Object} config Mock file system configuration.
@@ -125,6 +141,8 @@ exports = module.exports = function mock(config, options) {
 
   overrideBinding(binding);
 
+  overrideReadFileContext(binding);
+
   let currentPath = process.cwd();
   overrideProcess(
     function cwd() {
@@ -167,6 +185,7 @@ exports.restore = function() {
   restoreBinding();
   restoreProcess();
   restoreCreateWriteStream();
+  restoreReadFileContext();
 };
 
 /**

lib/readfilecontext.js

@@ -0,0 +1,152 @@
+'use strict';
+
+const {AbortError} = require('./error');
+const {FSReqCallback} = process.binding('fs');
+
+/**
+ * This is a workaround for getting access to the ReadFileContext
+ * prototype, which we need to be able to patch its methods.
+ * @returns {object}
+ */
+exports.getReadFileContextPrototype = function() {
+  const fs = require('fs');
+  const fsBinding = process.binding('fs');
+
+  const originalOpen = fsBinding.open;
+
+  let proto;
+  fsBinding.open = (_path, _flags, _mode, req) => {
+    proto = Object.getPrototypeOf(req.context);
+  };
+
+  fs.readFile('/ignored.txt', () => {});
+
+  fsBinding.open = originalOpen;
+
+  return proto;
+};
+
+/**
+ * This patches the ReadFileContext prototype to use mocked bindings
+ * when available. This entire implementation is more or less fully
+ * copied over from Node.js's /lib/internal/fs/read_file_context.js
+ *
+ * This patch is required to support Node.js v16+, where the ReadFileContext
+ * closes directly over the internal fs bindings, and is also eagerly loader.
+ *
+ * See https://github.com/tschaub/mock-fs/issues/332 for more information.
+ *
+ * @param {object} prototype The ReadFileContext prototype object to patch.
+ */
+exports.patchReadFileContext = function(prototype) {
+  const origRead = prototype.read;
+  const origClose = prototype.close;
+
+  const kReadFileUnknownBufferLength = 64 * 1024;
+  const kReadFileBufferLength = 512 * 1024;
+
+  function readFileAfterRead(err, bytesRead) {
+    const context = this.context;
+
+    if (err) {
+      return context.close(err);
+    }
+    context.pos += bytesRead;
+
+    if (context.pos === context.size || bytesRead === 0) {
+      context.close();
+    } else {
+      if (context.size === 0) {
+        // Unknown size, just read until we don't get bytes.
+        const buffer =
+          bytesRead === kReadFileUnknownBufferLength
+            ? context.buffer
+            : context.buffer.slice(0, bytesRead);
+        Array.prototype.push.apply(context.buffers, buffer);
+      }
+      context.read();
+    }
+  }
+
+  function readFileAfterClose(err) {
+    const context = this.context;
+    const callback = context.callback;
+    let buffer = null;
+
+    if (context.err || err) {
+      // This is a simplification from Node.js, where we don't bother merging the errors
+      return callback(context.err || err);
+    }
+
+    try {
+      if (context.size === 0) {
+        buffer = Buffer.concat(context.buffers, context.pos);
+      } else if (context.pos < context.size) {
+        buffer = context.buffer.slice(0, context.pos);
+      } else {
+        buffer = context.buffer;
+      }
+
+      if (context.encoding) {
+        buffer = buffer.toString(context.encoding);
+      }
+    } catch (err) {
+      return callback(err);
+    }
+
+    callback(null, buffer);
+  }
+
+  prototype.read = function read() {
+    if (!prototype._mockedBinding) {
+      return origRead.apply(this, arguments);
+    }
+
+    let buffer;
+    let offset;
+    let length;
+
+    if (this.signal && this.signal.aborted) {
+      return this.close(new AbortError());
+    }
+    if (this.size === 0) {
+      buffer = Buffer.allocUnsafeSlow(kReadFileUnknownBufferLength);
+      offset = 0;
+      length = kReadFileUnknownBufferLength;
+      this.buffer = buffer;
+    } else {
+      buffer = this.buffer;
+      offset = this.pos;
+      length = Math.min(kReadFileBufferLength, this.size - this.pos);
+    }
+
+    const req = new FSReqCallback();
+    req.oncomplete = readFileAfterRead;
+    req.context = this;
+
+    // This call and the one in close() is what we want to change, the
+    // rest is pretty much the same as Node.js except we don't have access
+    // to some of the internal optimizations.
+    prototype._mockedBinding.read(this.fd, buffer, offset, length, -1, req);
+  };
+
+  prototype.close = function close(err) {
+    if (!prototype._mockedBinding) {
+      return origClose.apply(this, arguments);
+    }
+
+    if (this.isUserFd) {
+      process.nextTick(function tick(context) {
+        readFileAfterClose.apply({context}, [null]);
+      }, this);
+      return;
+    }
+
+    const req = new FSReqCallback();
+    req.oncomplete = readFileAfterClose;
+    req.context = this;
+    this.err = err;
+
+    prototype._mockedBinding.close(this.fd, req);
+  };
+};