[Regression] CS0012: ReadOnlySpan (System.Memory) missing in Editor causes compilation failure for SentrySdk.Metrics in 4.6.0

[gal20040]

SDK Version

4.6.0

Unity Version

6000.3.15f1

Platform

• Editor
• Mobile (Android, iOS)
• Desktop (Windows, macOS, Linux)
• WebGL
• Console

Sentry Environment

Sentry SaaS (sentry.io)

Other Error Monitoring Solution

Yes

Steps to Reproduce

Description

After upgrading Sentry Unity SDK 4.5.0 -> 4.6.0, compiling any script that interacts with SentrySdk.Metrics (e.g., EmitCounter, EmitGauge) throws a CS0012 compilation error in the Unity Editor: error CS0012: The type 'ReadOnlySpan<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Memory, Version=4.0.1.2, Culture=neutral, PublicKeyToken=null'.

This seems to be a regression caused by the recent assembly aliasing removal (PR #2726 / Issue #2717). While fixing IL2CPP issues, System.Memory.dll was left disabled for the Editor platform in its .meta file. Because SentrySdk.Metrics methods contain overloads/signatures that require ReadOnlySpan<>, the C# compiler fails to resolve the overload resolution candidates during Editor compilation, explicitly demanding System.Memory, Version=4.0.1.2.

Steps to Reproduce

1. Install Sentry Unity SDK 4.6.0 in a Unity project, Packages\manifest.json:

   {
     "dependencies": {
       ...
       "io.sentry.unity": "https://github.com/getsentry/unity.git#4.6.0",
       ...
     }
   }

2. Create a custom .asmdef that references io.sentry.unity.runtime.
3. Create a C# script inside this assembly and call a metric method:

   SentrySdk.Metrics.EmitCounter("test_counter", 1.0, new[] { new KeyValuePair<string, object>("key", "value") });

4. Switch back to Unity to trigger compilation.

Environment

• Sentry Unity SDK Version: 4.6.0
• API Compatibility Level: .NET Standard 2.1
• Platform: Unity Editor (Windows)
• Unity: 6000.3.15f1 (c1aa84e375f6)

Expected vs Actual Result

Expected Behavior

The code should compile successfully in the Editor, just as it did in 4.5.0.

Actual Behavior

The Unity console throws the following compilation error: error CS0012: The type 'ReadOnlySpan<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Memory, Version=4.0.1.2, Culture=neutral, PublicKeyToken=null'.

[linear-code]

UNITY-229

[bitsandfoxes]

Hey @gal20040, thanks for raising this. I'll be working on getting this resolved asap.

[bitsandfoxes]

I think I've figured it out. So what's happening is

Aliasing

Even tho we exclude those four assemblies from being renamed, piping them through the Assembly Alias sets their PublicKeyToken to null. Testing this made me realize that we're already skipping renaming them here

sentry-unity/scripts/alias-assemblies.ps1

Line 22 in cadbf42

--assemblies-to-exclude "System.Buffers;System.Memory;System.Numerics.Vectors;System.Threading.Tasks.Extensions"

because we let Unity sort it out. But if Unity already comes with those, we don't even need to bundle them in.
That mean's we will have to go a step further and omit those from being part of the package.

Ambiguity Issue

There will be a secondary issue when emitting metrics like so

SentrySdk.Metrics.EmitCounter("hi", 1, new[] { new KeyValuePair<string, object>("yes", "no") });

This will trigger a

Ambiguous invocation.
Candidates are:
    EmitCounter<int>(string, int, IEnumerable<KeyValuePair<string,object>>?, Scope?)
    EmitCounter<int>(string, int, ReadOnlySpan<KeyValuePair<string,object>>, Scope?)
    all from class SentryMetricEmitter

We'll address this as part of getsentry/sentry-dotnet#5347
In the meantime (once the aliasing is addressed) you'll be able to unblock yourself with something like

var kv = new List<KeyValuePair<string, object>> { new("yes", "no")};    
SentrySdk.Metrics.EmitCounter("hi", 1, kv);