Add dir.contents for Memory and get tests passing

lib/Memory/Dir.js

@@ -9,11 +9,6 @@ var File = require('./File.js');
 var UnderlyingFilesystem = require('./UnderlyingFilesystem.js');
 
 var join = function(ufsPath, extraPath) {
-  // TODO: The leading / might eliminate this edge case.
-  if (ufsPath === '') {
-    return extraPath;
-  }
-
   return ufsPath + '/' + extraPath;
 };
 
@@ -34,11 +29,13 @@ var Dir = function(ufs, ufsPath) {
     return File(ufs, join(ufsPath, fpath));
   };
 
-  // TODO: dir.contents
+  dir.contents = function() {
+    return ufs.dirContents(ufsPath); // TODO: test throw when asking for contents of file
+  };
 
   return dir;
 };
 
 module.exports = function() {
-  return Dir(UnderlyingFilesystem(), '');
+  return Dir(UnderlyingFilesystem(), 'root');
 };

lib/Memory/UnderlyingFilesystem.js

@@ -63,12 +63,18 @@ module.exports = function() {
   ufs.existsFile = function(ufsPath) {
     assert(afsPath.check(ufsPath));
 
-    // TODO: If there is a directory collision, should this reject? Should the contract of exists
-    // be that false means you should be able to write to that location without overwriting, with
-    // the unavoidable caveat of something else being written there during asynchronous delays? Or
-    // should the result be false if there is a directory in the way?
-
     return delay().then(function() {
+      // TODO: If there is a directory collision, should this really reject? It seemed natural when
+      // writing the System implementation. Should the contract of exists be that false means you
+      // should be able to write to that location without overwriting, with the unavoidable caveat
+      // of something else being written there during asynchronous delays? Or should the result be
+      // false if there is a directory in the way?
+      if (Object.keys(files).some(function(filePath) {
+        return isPrefix(filePath + '/', ufsPath);
+      })) {
+        throw new Error('This file is blocked by another file path.');
+      }
+
       return !!files[ufsPath];
     });
   };
@@ -83,5 +89,35 @@ module.exports = function() {
     });
   };
 
+  var dirContents = function(ufsPath) {
+    var fullContents = Object.keys(files).filter(function(filePath) {
+      return isPrefix(ufsPath + '/', filePath);
+    }).map(function(filePath) {
+      return filePath.replace(ufsPath + '/', '');
+    });
+
+    var subdirs = [];
+    var dirFiles = [];
+
+    fullContents.forEach(function(filePath) {
+      if (filePath.indexOf('/') !== -1) {
+        subdirs.push(filePath.split('/')[0]);
+      } else {
+        dirFiles.push(filePath);
+      }
+    });
+
+    return {
+      dirs: uniq(subdirs),
+      files: dirFiles.sort()
+    };
+  };
+
+  ufs.dirContents = function(ufsPath) {
+    return delay().then(function() {
+      return dirContents(ufsPath);
+    });
+  };
+
   return ufs;
 };

test/Memory.js

@@ -8,7 +8,7 @@ var describeDir = require('./describers/dir.js');
 var describeFile = require('./describers/file.js');
 
 describe('Memory', function() {
-  xdescribe('Dir', function() {
+  describe('Dir', function() {
     describeDir(Memory.Dir, 2);
   });