Fix #558 - Implementing fs.access() method (#560)

* Implementing fs.access() method

* added new line to access.js

* updated requested changes

* updated README.md with fs.access

* fixing truncate error

* updated README.md

* changed access.js to access.spec.js

README.md

@@ -305,6 +305,7 @@ var fs = new Filer.FileSystem();
 * [fs.mknod(path, mode, callback)](#mknod)
 * [fs.rmdir(path, callback)](#rmdir)
 * [fs.mkdir(path, [mode], callback)](#mkdir)
+* [fs.access(path, [mode], callback)](#access)
 * [fs.readdir(path, callback)](#readdir)
 * [fs.close(fd, callback)](#close)
 * [fs.open(path, flags, [mode], callback)](#open)
@@ -672,6 +673,26 @@ fs.mkdir('/home', function(err) {
 });
 ```
 
+#### fs.access(path, [mode], callback)<a name="access"></a>
+
+Tests a user's permissions for the file or directory supplied in `path` argument. Asynchronous [access(2)](http://pubs.opengroup.org/onlinepubs/009695399/functions/access.html). Callback gets no additional arguments. The `mode` argument can be one of the following (constants are available on `fs.constants`):
+
+* `F_OK`: Test for existence of file.
+* `R_OK`: Test whether the file exists and grants read permission.
+* `W_OK`: Test whether the file exists and grants write permission.
+* `X_OK`: Test whether the file exists and grants execute permission.
+
+NOTE: you can also create a mask consisting of the bitwise OR of two or more values (e.g. `fs.constants.W_OK | fs.constants.R_OK`).
+
+Example:
+
+```javascript
+// Check if the file exists in the current directory.
+fs.access(file, fs.constants.F_OK, function(err) {
+  console.log(`${file} ${err ? 'does not exist' : 'exists'}`);
+});
+```
+
 #### fs.readdir(path, callback)<a name="readdir"></a>
 
 Reads the contents of a directory. Asynchronous [readdir(3)](http://pubs.opengroup.org/onlinepubs/009695399/functions/readdir.html).

src/filesystem/implementation.js

@@ -441,6 +441,20 @@ function make_directory(context, path, callback) {
   find_node(context, path, check_if_directory_exists);
 }
 
+function access_file(context, path, mode, callback) {
+  path = normalize(path);
+  find_node(context, path, function (err) {
+    if (err) {
+      return callback(err);
+    }
+    /* 
+    TODO: we currently only support Constants.fsConstants.F_OK
+    Working to fix the issue: https://github.com/filerjs/filer/issues/561
+    */
+    callback(null);
+  });
+}
+
 /**
  * remove_directory
  */
@@ -1685,6 +1699,17 @@ function mkdir(fs, context, path, mode, callback) {
   make_directory(context, path, callback);
 }
 
+function access(fs, context, path, mode, callback) {
+  if (typeof mode === 'function') {
+    callback = mode;
+    mode = Constants.fsConstants.F_OK;
+  }
+
+  if (!pathCheck(path, callback)) return;
+  mode = mode | 0;
+  access_file(context, path, mode, callback);
+}
+
 function rmdir(fs, context, path, callback) {
   if(!pathCheck(path, callback)) return;
   remove_directory(context, path, callback);
@@ -2385,6 +2410,7 @@ module.exports = {
   ensureRootDirectory: ensure_root_directory,
   open: open,
   chmod: chmod,
+  access: access,
   fchmod: fchmod,
   chown: chown,
   fchown: fchown,

src/filesystem/interface.js

@@ -269,6 +269,7 @@ function FileSystem(options, callback) {
   */
   [
     'open',
+    'access',
     'chmod',
     'fchmod',
     'chown',

tests/index.js

@@ -9,6 +9,7 @@ require('./spec/filer.spec');
 // Filer.FileSystem.*
 require('./spec/filer.filesystem.spec');
 require('./spec/fs.spec');
+require('./spec/fs.access.spec');
 require('./spec/fs.stat.spec');
 require('./spec/fs.lstat.spec');
 require('./spec/fs.exists.spec');

tests/spec/fs.access.spec.js

@@ -0,0 +1,37 @@
+var util = require('../lib/test-utils.js');
+var expect = require('chai').expect;
+
+describe('fs.access', function () {
+  beforeEach(util.setup);
+  afterEach(util.cleanup);
+
+  it('should be a function', function () {
+    var fs = util.fs();
+    expect(typeof fs.access).to.equal('function');
+  });
+
+  it('should return an error if file does not exist', function (done) {
+    var fs = util.fs();
+
+    fs.access('/tmp', fs.constants.F_OK, function (error) {
+      expect(error).to.exist;
+      expect(error.code).to.equal('ENOENT');
+      done();
+    });
+  });
+
+  it('should return no error if file does exist', function (done) {
+    var fs = util.fs();
+    var contents = 'This is a file.';
+
+    fs.writeFile('/myfile', contents, function (error) {
+      if (error) throw error;
+
+      fs.access('/myfile', fs.constants.F_OK, function (error) {
+        expect(error).not.to.exist;
+        done();
+      });
+    });
+  });
+
+});