Handle Stream throwing for Length (#995)

docs/naming.md

@@ -617,7 +617,7 @@ public static string NameWithParent(this Type type)
     return type.Name;
 }
 ```
-<sup><a href='/src/Verify/Extensions.cs#L67-L79' title='Snippet source file'>snippet source</a> | <a href='#snippet-namewithparent' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Verify/Extensions.cs#L99-L111' title='Snippet source file'>snippet source</a> | <a href='#snippet-namewithparent' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 

docs/verify-file.md

@@ -16,7 +16,7 @@ Verifies the contents of a file.
 public Task VerifyFilePath() =>
     VerifyFile("sample.txt");
 ```
-<sup><a href='/src/Verify.Tests/StreamTests.cs#L175-L181' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfile' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Verify.Tests/StreamTests.cs#L176-L182' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfile' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 
@@ -33,7 +33,7 @@ public Task VerifyFileWithInfo() =>
         "sample.txt",
         info: "the info");
 ```
-<sup><a href='/src/Verify.Tests/StreamTests.cs#L194-L202' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfilewithinfo' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Verify.Tests/StreamTests.cs#L195-L203' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfilewithinfo' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 

docs/verify-xml.md

@@ -19,7 +19,7 @@ Verifies Xml:
 public Task VerifyFilePath() =>
     VerifyFile("sample.txt");
 ```
-<sup><a href='/src/Verify.Tests/StreamTests.cs#L175-L181' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfile' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Verify.Tests/StreamTests.cs#L176-L182' title='Snippet source file'>snippet source</a> | <a href='#snippet-verifyfile' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 

src/Verify.Tests/UnboundedStream.cs → src/Verify.Tests/NoLengthStream.cs

@@ -1,5 +1,5 @@
-class UnboundedStream :
-    MemoryStream
+class NoLengthStream(byte[] bytes) :
+    MemoryStream(bytes)
 {
     public override long Length => throw new NotImplementedException();
 }

src/Verify.Tests/StreamTests.NoLengthStream.verified.bin

@@ -0,0 +1 @@
+

src/Verify.Tests/StreamTests.cs

@@ -124,13 +124,14 @@ public Task StreamNotAtStartAsText()
     }
 
     [Fact]
-    public Task UnboundedStream()
+    public Task NoLengthStream()
     {
-        var stream = new UnboundedStream();
+        var stream = new NoLengthStream(new byte[]
+        {
+            1
+        });
 
-        return ThrowsTask(() => Verify(stream))
-            .DisableRequireUniquePrefix()
-            .IgnoreStackTrace();
+        return Verify(stream);
     }
 
     [Fact]

src/Verify/Compare/FileComparer.cs

@@ -20,7 +20,7 @@ public static async Task<EqualityResult> DoCompare(VerifySettings settings, File
             return await InnerCompare(file, receivedStream, (s1, s2) => compare(s1, s2, settings.Context));
         }
 
-        if (receivedStream.CanSeek &&
+        if (receivedStream.CanSeekAndReadLength() &&
             IoHelpers.Length(file.VerifiedPath) != receivedStream.Length)
         {
             await IoHelpers.WriteStream(file.ReceivedPath, receivedStream);
@@ -66,14 +66,14 @@ async Task<EqualityResult> EqualityResult(Stream receivedStream, Stream verified
             return new(Equality.NotEqual, compareResult.Message, null, null);
         }
 
-        if (receivedStream.CanSeek)
+        if (receivedStream.CanSeekAndReadLength())
         {
             receivedStream.MoveToStart();
             return await EqualityResult(receivedStream, verifiedStream);
         }
 
         using var memoryStream = new MemoryStream();
-        await receivedStream.CopyToAsync(memoryStream);
+        await receivedStream.SafeCopy(memoryStream);
         memoryStream.MoveToStart();
 
         return await EqualityResult(memoryStream, verifiedStream);

src/Verify/Extensions.cs

@@ -1,4 +1,5 @@
-static class Extensions
+// ReSharper disable UnusedVariable
+static class Extensions
 {
     public static string Extension(this FileStream file) =>
         FileExtensions.GetExtension(file.Name);
@@ -17,6 +18,37 @@ public static async Task<List<T>> ToList<T>(this IAsyncEnumerable<T> target)
         return list;
     }
 
+    // Streams can throw for Length. Eg a http stream that the server has not specified the length header
+    // Specify buffer to avoid an exception in Stream.CopyToAsync where it reads Length
+    // https://github.com/dotnet/runtime/issues/43448
+    public static Task SafeCopy(this Stream source, Stream target)
+    {
+        if (source.CanReadLength())
+        {
+            return source.CopyToAsync(target);
+        }
+
+        return source.CopyToAsync(target, 81920);
+    }
+
+    public static bool CanSeekAndReadLength(this Stream stream) =>
+        stream.CanSeek &&
+        CanReadLength(stream);
+
+    static bool CanReadLength(this Stream stream)
+    {
+        try
+        {
+            var streamLength = stream.Length;
+        }
+        catch (NotImplementedException)
+        {
+            return false;
+        }
+
+        return true;
+    }
+
     public static string TrimPreamble(this string text) =>
         text.TrimStart('\uFEFF');
 

src/Verify/IoHelpers.cs

@@ -218,7 +218,8 @@ public static async Task WriteStream(string path, Stream stream)
         if (!TryCopyFileStream(path, stream))
         {
             await using var targetStream = OpenWrite(path);
-            await stream.CopyToAsync(targetStream);
+            await stream.SafeCopy(targetStream);
+            HandleEmptyFile(path);
         }
     }
 
@@ -236,9 +237,18 @@ public static async Task WriteStream(string path, Stream stream)
         if (!TryCopyFileStream(path, stream))
         {
             using var targetStream = OpenWrite(path);
-            await stream.CopyToAsync(targetStream);
+            await stream.SafeCopy(targetStream);
+            HandleEmptyFile(path);
         }
     }
 
 #endif
+
+    static void HandleEmptyFile(string path)
+    {
+        if (new FileInfo(path).Length == 0)
+        {
+            throw new("Empty data is not allowed.");
+        }
+    }
 }

src/Verify/Verifier/InnerVerifier_Stream.cs

@@ -84,24 +84,6 @@ public async Task<VerifyResult> VerifyStream(Stream? stream, string extension, o
 
         using (stream)
         {
-            long GetLength()
-            {
-                try
-                {
-                    return stream.Length;
-                }
-                catch (NotImplementedException)
-                {
-                    throw new("Could not read Length property of target stream. Verify does not support unbounded streams.");
-                }
-            }
-
-            var length = GetLength();
-            if (length == 0)
-            {
-                throw new("Empty data is not allowed.");
-            }
-
             if (VerifierSettings.HasExtensionConverter(extension))
             {
                 var (newInfo, converted, cleanup) = await DoExtensionConversion(extension, stream, info);