Introduce BlobAlreadyExistsException

framework/src/Volo.Abp.BlobStoring.FileSystem/Volo/Abp/BlobStoring/FileSystem/FileSystemBlobProvider.cs

@@ -6,7 +6,7 @@ using Volo.Abp.IO;
 namespace Volo.Abp.BlobStoring.FileSystem
 {
     //TODO: What if the file is being used on create, delete or read?
-    //TODO: Implement all methods truly async!
+    //TODO: Implement all methods truly async (if possible)!
 
     public class FileSystemBlobProvider : BlobProviderBase, ITransientDependency
     {
@@ -21,6 +21,11 @@ namespace Volo.Abp.BlobStoring.FileSystem
         {
             var filePath = FilePathCalculator.Calculate(args);
 
+            if (!args.OverrideExisting && await ExistsAsync(filePath))
+            {
+                throw new BlobAlreadyExistsException($"Saving BLOB '{args.BlobName}' does already exists in the container '{args.ContainerName}'! Set {nameof(args.OverrideExisting)} if it should be overwritten.");
+            }
+            
             DirectoryHelper.CreateIfNotExists(Path.GetDirectoryName(filePath));
 
             var fileMode = args.OverrideExisting
@@ -29,8 +34,6 @@ namespace Volo.Abp.BlobStoring.FileSystem
             
             using (var fileStream = File.Open(filePath, fileMode, FileAccess.Write))
             {
-                //TODO: Truely implement this (like this? http://writeasync.net/?p=2621 or https://www.infoworld.com/article/2995387/how-to-perform-asynchronous-file-operations-in-c.html)
-                
                 await args.BlobStream.CopyToAsync(
                     fileStream,
                     args.CancellationToken
@@ -43,15 +46,13 @@ namespace Volo.Abp.BlobStoring.FileSystem
         public override Task<bool> DeleteAsync(BlobProviderDeleteArgs args)
         {
             var filePath = FilePathCalculator.Calculate(args);
-            
             return Task.FromResult(FileHelper.DeleteIfExists(filePath));
         }
 
         public override Task<bool> ExistsAsync(BlobProviderExistsArgs args)
         {
             var filePath = FilePathCalculator.Calculate(args);
-
-            return Task.FromResult(File.Exists(filePath));
+            return ExistsAsync(filePath);
         }
 
         public override Task<Stream> GetOrNullAsync(BlobProviderGetArgs args)
@@ -65,5 +66,10 @@ namespace Volo.Abp.BlobStoring.FileSystem
 
             return Task.FromResult<Stream>(File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.Read));
         }
+        
+        protected virtual Task<bool> ExistsAsync(string filePath)
+        {
+            return Task.FromResult(File.Exists(filePath));
+        }
     }
 }

framework/src/Volo.Abp.BlobStoring/Volo/Abp/BlobStoring/BlobAlreadyExistsException.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Runtime.Serialization;
+
+namespace Volo.Abp.BlobStoring
+{
+    public class BlobAlreadyExistsException : AbpException
+    {
+        public BlobAlreadyExistsException()
+        {
+
+        }
+
+        public BlobAlreadyExistsException(string message)
+            : base(message)
+        {
+
+        }
+
+        public BlobAlreadyExistsException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+
+        }
+
+        public BlobAlreadyExistsException(SerializationInfo serializationInfo, StreamingContext context)
+            : base(serializationInfo, context)
+        {
+
+        }
+    }
+}

framework/test/Volo.Abp.BlobStoring.Tests/Volo/Abp/BlobStoring/BlobContainer_Tests.cs

@@ -37,6 +37,35 @@ namespace Volo.Abp.BlobStoring
             result.SequenceEqual(testContent).ShouldBeTrue();
         }
 
+        [Fact]
+        public async Task Should_Overwrite_Pre_Saved_Blob_If_Requested()
+        {
+            var blobName = "test-blob-1";
+            
+            var testContent = "test content".GetBytes();
+            await Container.SaveAsync(blobName, testContent);
+            
+            var testContentOverwritten = "test content overwritten".GetBytes();
+            await Container.SaveAsync(blobName, testContentOverwritten, true);
+            
+            var result = await Container.GetAllBytesAsync(blobName);
+            result.SequenceEqual(testContentOverwritten).ShouldBeTrue();
+        }
+        
+        [Fact]
+        public async Task Should_Not_Allow_To_Overwrite_Pre_Saved_Blob_By_Default()
+        {
+            var blobName = "test-blob-1";
+            
+            var testContent = "test content".GetBytes();
+            await Container.SaveAsync(blobName, testContent);
+            
+            var testContentOverwritten = "test content overwritten".GetBytes();
+            await Assert.ThrowsAsync<BlobAlreadyExistsException>(() =>
+                Container.SaveAsync(blobName, testContentOverwritten)
+            );
+        }
+        
         [Theory]
         [InlineData("test-blob-1")]
         [InlineData("test-blob-1.txt")]