Address self review

Add also useful methods to use with this one

Common/Storage/ObjectStore.cs

@@ -1,4 +1,4 @@
-/*
+/*
  * QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
  * Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
  *
@@ -124,7 +124,8 @@ namespace QuantConnect.Storage
         {
             encoding = encoding ?? Encoding.UTF8;
 
-            return encoding.GetString(_store.ReadBytes(key));
+            var data = _store.ReadBytes(key);
+            return data != null ? encoding.GetString(data) : null;
         }
 
         /// <summary>
@@ -172,17 +173,35 @@ namespace QuantConnect.Storage
             }
         }
 
+        /// <summary>
+        /// Saves the data from a local file path associated with the specified key
+        /// </summary>
+        /// <remarks>If the file does not exist it will throw an exception</remarks>
+        /// <param name="key">The object key</param>
+        /// <returns>True if the object was saved successfully</returns>
+        public bool Save(string key)
+        {
+            // Check the file exists
+            var filePath = GetFilePath(key);
+            if (!File.Exists(filePath))
+            {
+                throw new ArgumentException($"There is no file associated with key {key} in '{filePath}'");
+            }
+            var bytes = File.ReadAllBytes(filePath);
+
+            return _store.SaveBytes(key, bytes);
+        }
+
         /// <summary>
         /// Saves the object data in text format for the specified key
         /// </summary>
         /// <param name="key">The object key</param>
         /// <param name="text">The string object to be saved</param>
-        /// <param name="encoding">The string encoding used</param>
+        /// <param name="encoding">The string encoding used, <see cref="Encoding.UTF8"/> by default</param>
         /// <returns>True if the object was saved successfully</returns>
         public bool Save(string key, string text, Encoding encoding = null)
         {
-            encoding = encoding ?? Encoding.UTF8;
-
+            encoding ??= Encoding.UTF8;
             return _store.SaveBytes(key, encoding.GetBytes(text));
         }
 

Engine/Storage/LocalObjectStore.cs

@@ -1,4 +1,4 @@
-/*
+/*
  * QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
  * Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
  *
@@ -203,7 +203,7 @@ namespace QuantConnect.Lean.Engine.Storage
             // Before saving confirm we are abiding by the control rules
             // Start by counting our file and its length
             var fileCount = 1;
-            var expectedStorageSizeBytes = contents.Length;
+            var expectedStorageSizeBytes = contents?.Length ?? 0;
             foreach (var kvp in _storage)
             {
                 if (key.Equals(kvp.Key))
@@ -214,7 +214,10 @@ namespace QuantConnect.Lean.Engine.Storage
                 else
                 {
                     fileCount++;
-                    expectedStorageSizeBytes += kvp.Value.Length;
+                    if(kvp.Value != null)
+                    {
+                        expectedStorageSizeBytes += kvp.Value.Length;
+                    }
                 }
             }
 
@@ -277,6 +280,8 @@ namespace QuantConnect.Lean.Engine.Storage
         /// <summary>
         /// Returns the file path for the specified key
         /// </summary>
+        /// <remarks>If the key is not already inserted it will just return a path associated with it
+        /// and add the key with null value</remarks>
         /// <param name="key">The object key</param>
         /// <returns>The path for the file</returns>
         public virtual string GetFilePath(string key)
@@ -284,13 +289,15 @@ namespace QuantConnect.Lean.Engine.Storage
             // Ensure we have an object for that key
             if (!ContainsKey(key))
             {
-                throw new KeyNotFoundException($"Object with key '{key}' was not found in the current project. " +
-                    "Please use ObjectStore.ContainsKey(key) to check if an object exists before attempting to read."
-                );
+                // Add a key with null value to tell Persist() not to delete the file created in the path associated
+                // with this key and not update it with the value associated with the key(null)
+                SaveBytes(key, null);
+            }
+            else
+            {
+                // Persist to ensure pur files are up to date
+                Persist();
             }
-
-            // Persist to ensure pur files are up to date
-            Persist();
 
             // Fetch the path to file and return it
             return PathForKey(key);
@@ -414,9 +421,13 @@ namespace QuantConnect.Lean.Engine.Storage
                 // Write all our store data to disk
                 foreach (var kvp in data)
                 {
-                    // Get a path for this key and write to it
-                    var path = PathForKey(kvp.Key);
-                    File.WriteAllBytes(path, kvp.Value);
+                    // Skip the key associated with null values. They are not linked to a file yet
+                    if (kvp.Value != null)
+                    {
+                        // Get a path for this key and write to it
+                        var path = PathForKey(kvp.Key);
+                        File.WriteAllBytes(path, kvp.Value);
+                    }
                 }
 
                 return true;

Tests/Common/Storage/LocalObjectStoreTests.cs

@@ -1,4 +1,4 @@
-/*
+/*
  * QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
  * Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
  *
@@ -68,7 +68,7 @@ namespace QuantConnect.Tests.Common.Storage
             Log.LogHandler = _logHandler;
         }
 
-        [TestCase(FileAccess.Read, false)]
+        [TestCase(FileAccess.Read, true)]
         [TestCase(FileAccess.ReadWrite, false)]
         [TestCase(0, true)]
         [TestCase(FileAccess.Write, true)]
@@ -83,7 +83,7 @@ namespace QuantConnect.Tests.Common.Storage
             }
             else
             {
-                Assert.Throws<KeyNotFoundException>(() => store.GetFilePath("Jose"));
+                Assert.DoesNotThrow(() => store.GetFilePath("Jose"));
             }
         }
 
@@ -250,7 +250,6 @@ namespace QuantConnect.Tests.Common.Storage
         public void GetFilePathReturnsFileName(string key, string expectedRelativePath)
         {
             var expectedPath = Path.GetFullPath(expectedRelativePath).Replace("\\", "/");
-            _store.SaveString(key, "data");
             Assert.AreEqual(expectedPath, _store.GetFilePath(key).Replace("\\", "/"));
         }
 
@@ -412,6 +411,55 @@ namespace QuantConnect.Tests.Common.Storage
             Assert.IsFalse(_store.SaveString("breaker", "gotem"));
         }
 
+        [Test]
+        public void WriteFromExternalMethodAndSaveFromSource()
+        {
+            using (var store = new ObjectStore(new LocalObjectStore()))
+            {
+                store.Initialize("test", 0, 0, "", new Controls() { PersistenceIntervalSeconds = -1 });
+                Assert.IsTrue(Directory.Exists("./LocalObjectStoreTests/test"));
+
+                var key = "Test";
+                var content = "Example text";
+
+                var path = store.GetFilePath(key);
+
+                DummyMachineLearning(path, content);
+                store.Save(key);
+
+                var storeContent = store.Read(key);
+                Assert.AreEqual(content, storeContent);
+            }
+        }
+
+        [Test]
+        public void GetFilePathMethodWorksProperly()
+        {
+            using (var store = new ObjectStore(new LocalObjectStore()))
+            {
+                store.Initialize("test", 0, 0, "", new Controls() { PersistenceIntervalSeconds = -1 });
+                Assert.IsTrue(Directory.Exists("./LocalObjectStoreTests/test"));
+
+                var key = "test";
+                var path = store.GetFilePath(key);
+                Assert.IsFalse(File.Exists(path));
+                Assert.IsNull(store.Read(key));
+            }
+        }
+
+        [Test]
+        public void TrySaveKeyWithNotFileAssociated()
+        {
+            using (var store = new ObjectStore(new LocalObjectStore()))
+            {
+                store.Initialize("test", 0, 0, "", new Controls() { PersistenceIntervalSeconds = -1 });
+                Assert.IsTrue(Directory.Exists("./LocalObjectStoreTests/test"));
+
+                var key = "test";
+                Assert.Throws<Exception>(() => store.Save(key));
+            }
+        }
+
         [Test]
         public void DeletedObjectIsNotReloaded()
         {
@@ -448,6 +496,20 @@ namespace QuantConnect.Tests.Common.Storage
             }
         }
 
+        private static void DummyMachineLearning(string outputFile, string content)
+        {
+            try
+            {
+                var sw = new StreamWriter(outputFile);
+                sw.Write(content);
+                sw.Close();
+            }
+            catch(Exception e)
+            {
+                throw e;
+            }
+        }
+
         public class TestSettings
         {
             public int EmaFastPeriod { get; set; }