Files.app: Handles corner cases in NewMetadataProvider.

The CL adds:
 * Assertion for property names passed to NewMetadataProvider.
 * Existance check for results obtained from getImpl.

BUG=410766
TEST=FileManagerJsTest.NewMetadataProvider

Review URL: https://codereview.chromium.org/899603002

Cr-Commit-Position: refs/heads/master@{#314297}

ui/file_manager/file_manager/foreground/js/metadata/new_metadata_provider.js

@@ -5,17 +5,29 @@
 /**
  * TODO(hirono): Remove 'New' from the name after removing old MetadataProvider.
  * @param {!MetadataProviderCache} cache
+ * @param {!Array<string>} validPropertyNames
  * @constructor
  * @struct
  * @template T
  */
-function NewMetadataProvider(cache) {
+function NewMetadataProvider(cache, validPropertyNames) {
   /**
    * @private {!MetadataProviderCache}
    * @const
    */
   this.cache_ = cache;
 
+  /**
+   * Set of valid property names. Key is the name of property and value is
+   * always true.
+   * @private {!Object<string, boolean>}
+   * @const
+   */
+  this.validPropertyNames_ = {};
+  for (var i = 0; i < validPropertyNames.length; i++) {
+    this.validPropertyNames_[validPropertyNames[i]] = true;
+  }
+
   /**
    * @private {!Array<!MetadataProviderCallbackRequest<T>>}
    * @const
@@ -25,8 +37,6 @@ function NewMetadataProvider(cache) {
 
 /**
  * Obtains the metadata for the request.
- * Note: this must return all the properties requested by the argument.
- * Otherwise Promise returned by NewMetadataProvider#get may not be fulfilled.
  * @param {!Array<!MetadataRequest>} requests
  * @return {!Promise<!Array<!T>>}
  * @protected
@@ -40,6 +50,11 @@ NewMetadataProvider.prototype.getImpl;
  * @return {!Promise<!Array<!T>>}
  */
 NewMetadataProvider.prototype.get = function(entries, names) {
+  // Check if the property name is correct or not.
+  for (var i = 0; i < names.length; i++) {
+    assert(this.validPropertyNames_[names[i]]);
+  }
+
   // Check if the results are cached or not.
   if (this.cache_.hasFreshCache(entries, names))
     return Promise.resolve(this.getCache(entries, names));
@@ -60,11 +75,19 @@ NewMetadataProvider.prototype.get = function(entries, names) {
 
   // If the requests are not empty, call the requests.
   if (requests.length) {
-    var requestedEntries = [];
-    for (var i = 0; i < requests.length; i++) {
-      requestedEntries.push(requests[i].entry);
-    }
     this.getImpl(requests).then(function(list) {
+      // Obtain requested entries and ensure all the requested properties are
+      // contained in the result.
+      var requestedEntries = [];
+      for (var i = 0; i < requests.length; i++) {
+        requestedEntries.push(requests[i].entry);
+        for (var j = 0; j < requests[i].names.length; j++) {
+          var name = requests[i].names[j];
+          if (!(name in list[i]))
+            list[i][name] = undefined;
+        }
+      }
+
       // Store cache.
       if (this.cache_.storeProperties(requestId, requestedEntries, list)) {
         // TODO(hirono): Dispatch metadata change event here.

ui/file_manager/file_manager/foreground/js/metadata/new_metadata_provider_unittest.html

@@ -7,6 +7,7 @@
 <script src="metadata_cache_set.js"></script>
 
 <!-- Others -->
+<script src="../../../../../../ui/webui/resources/js/assert.js"></script>
 <script src="../../../common/js/lru_cache.js"></script>
 <script src="../../../common/js/unittest_util.js"></script>
 <script src="metadata_cache_item.js"></script>

ui/file_manager/file_manager/foreground/js/metadata/new_metadata_provider_unittest.js

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 function TestMetadataProvider(cache) {
-  NewMetadataProvider.call(this, cache);
+  NewMetadataProvider.call(this, cache, ['property', 'propertyA', 'propertyB']);
   this.requestCount = 0;
 }
 
@@ -22,6 +22,18 @@ TestMetadataProvider.prototype.getImpl = function(requests) {
   }));
 };
 
+function TestEmptyMetadataProvider(cache) {
+  NewMetadataProvider.call(this, cache, ['property']);
+}
+
+TestEmptyMetadataProvider.prototype.__proto__ = NewMetadataProvider.prototype;
+
+TestEmptyMetadataProvider.prototype.getImpl = function(requests) {
+  return Promise.resolve(requests.map(function() {
+    return {};
+  }));
+};
+
 var entryA = {
   toURL: function() { return "filesystem://A"; }
 };
@@ -113,3 +125,20 @@ function testNewMetadataProviderGetCache(callback) {
     assertEquals('filesystem://A:property', cache[0].property);
   }), callback);
 }
+
+function testNewMetadataProviderUnknownProperty() {
+  var cache = new MetadataProviderCache();
+  var provider = new TestMetadataProvider(cache);
+  assertThrows(function() {
+    provider.get([entryA], ['unknown']);
+  });
+}
+
+function testNewMetadataProviderEmptyResult(callback) {
+  var cache = new MetadataProviderCache();
+  var provider = new TestEmptyMetadataProvider(cache);
+  // getImpl returns empty result.
+  reportPromise(provider.get([entryA], ['property']).then(function(results) {
+    assertEquals(undefined, results[0].property);
+  }), callback);
+}