JsonPatch - Tests on empty string throws exception

[Kjelli]

Describe the bug

I want to overwrite an existing json property that is an empty string "", and beforehand a test operation is performed. When testing that the value at path /foo is equal to "" - an exception is thrown with the following error message: The value at 'foo' cannot be null or empty to perform the test operation.

According to RFC6902 section 4.6, I believe it is incorrect to disallow values to be tested in this case.

To Reproduce

// Object with empty string property foo
dynamic myObject = new ExpandoObject();
myObject.foo = "";

// Create patch document with test operation
var doc = new JsonPatchDocument();
doc.Test("foo", "");

doc.ApplyTo(myObject); // <-- throws JsonPatchException

Exceptions (if any)

 Microsoft.AspNetCore.JsonPatch.Exceptions.JsonPatchException : The value at 'foo' cannot be null or empty to perform the test operation.

<.cctor>b__1_0(JsonPatchError error)
    ObjectAdapter.Test(Operation operation, Object objectToApplyTo)
    Operation.Apply(Object objectToApplyTo, IObjectAdapter adapter)
    JsonPatchDocument.ApplyTo(Object objectToApplyTo, IObjectAdapter adapter)
    JsonPatchDocument.ApplyTo(Object objectToApplyTo)
    UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)

Throw location: /src/Microsoft.AspNetCore.JsonPatch/Internal/DictionaryAdapterOfTU.cs

Further technical details

• ASP.NET Core version 3.1
• Microsoft.AspNetCore.JsonPatch 3.1.8

$ dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   3.1.401
 Commit:    5b6f5e5005

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19041
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.1.401\

Host (useful for support):
  Version: 3.1.7
  Commit:  fcfdef8d6b

.NET Core SDKs installed:
  3.1.200 [C:\Program Files\dotnet\sdk]
  3.1.401 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]       
  Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]        
  Microsoft.AspNetCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]       
  Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]        
  Microsoft.AspNetCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]        
  Microsoft.AspNetCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]        
  Microsoft.NETCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

[henriksen]

Same result on .NET 5

> dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.100
 Commit:    5044b93829

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.100\

Host (useful for support):
  Version: 5.0.0
  Commit:  cf258a14b7

[ghost]

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[TanayParikh]

Thanks, closing as duplicate of #25942