MessageReceiver.CompleteAsync with empty list throws ArgumentNullException

[WhiteRabbit68]

Actual Behavior

1. CompleteAsync(new List<string>())
2. throws ArgumentException with "Value cannot be null" ParamName=lockTokens

This is misleading because the parameter is NOT null. Why is it an error to supply an empty list? Just return without doing anything.

Expected Behavior

1. CompleteAsync(new List<string>())
2. No exception thrown

Versions

• OS platform and version: Windows
• .NET Version: Standard 2.0
• NuGet package version: 3.1.0

[SeanFeldman]

@WhiteRabbit68 while I don't disagree, it could go the other way - why don't you avoid unnecessary method invocation if there are no messages to complete? Worse if it's on the hot path.

Or would you prefer to see an exception with a different message that is more meaningful?

[WhiteRabbit68]

Sure, but avoiding unnecessary calls should be the responsibility of the client:
if (tokensToComplete.Any())
await receiver.CompleteAsync(tokensToComplete);

It seems strange that an API should throw exceptions just because it thinks it was called in vain, but I would rather have ArgumentException("Value cannot be empty list") that forces the check above if so.

In any case, erroneous error messages are very frustrating, just spent some time wondering how the list of tokens could be null.

[SeanFeldman]

The exception message is indeed incorrect. Fixing that.