Default Blazor WASM project should not produce trim warnings

[yugabe]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

The default project templates for Blazor WASM apps use trimming, but trimming warnings are suppressed by default. Enabling trim warnings shows there are a number of issues with how the API is annotated.

Unfortunately, there isn't guidance available on how to actually (correctly) fix the issues pointed to by these warnings.

Assuming that the application works correctly when trimmed in all cases, it means one or more of:

• the underlying APIs are incorrectly annotated,
• the underlying APIs or app are not suitable for trimming,
• the app produced by the default app template might break at runtime,
• the user is expected to fix the warnings, which are disabled by default, and there isn't sufficient guidance for them to do so (using the guidance referenced by the warnings the user won't be able to solve the issues correctly),
• warnings might be invalid.

Expected Behavior

The default project templates (at least) should be able to be published without trim warnings or there should be guidance on how to fix the warnings and point out in the documentation that this is the case (the default template isn't suitable for trimming).

Steps To Reproduce

dotnet new blazorwasm
dotnet publish -p:SuppressTrimAnalysisWarnings=false

Exceptions (if any)

All of the following warnings are issued.

ILLink : Trim analysis warning IL2111: BlazorTrimTest.App.<>c.<BuildRenderTree>b__0_1(RenderTreeBuilder): Method 'Microsoft.AspNetCore.Components.LayoutView.WrapInLayout(Type, RenderFragment)' with parameters or return value with `DynamicallyAccessedMembersAttribute` is accessed via reflection. Trimmer can't guarantee availability of the requirements o
f the method. [~\BlazorTrimTest\BlazorTrimTest.csproj]

ILLink : Trim analysis warning IL2111: BlazorTrimTest.App.<>c.<BuildRenderTree>b__0_1(RenderTreeBuilder): Method 'Microsoft.AspNetCore.Components.LayoutView.Layout.set' with parameters or return value with `DynamicallyAccessedMembersAttribute` is accessed via reflection. Trimmer can't guarantee availability of the requirements of the method. [~\BlazorTrimTest\BlazorTrimTest.csproj]

ILLink : Trim analysis warning IL2118: BlazorTrimTest.App.<>c.<BuildRenderTree>b__0_1(RenderTreeBuilder): Compiler-generated member 'Microsoft.AspNetCore.Components.LayoutView.<>c__DisplayClass13_0.<WrapInLayout>g__Render|0(RenderTreeBuilder)' is accessed via reflection. Trimmer can't guarantee availability of the requirements of the member. [~\BlazorTrimTest\BlazorTrimTest.csproj]

ILLink : Trim analysis warning IL2111: BlazorTrimTest.App.<>c.<BuildRenderTree>b__0_1(RenderTreeBuilder): Method 'Microsoft.AspNetCore.Components.LayoutView.Layout.set' with parameters or return value with `DynamicallyAccessedMembersAttribute` is accessed via reflection. Trimmer can't guarantee availability of the requirements of the method. [~\BlazorTrimTest\BlazorTrimTest.csproj]

ILLink : Trim analysis warning IL2110: BlazorTrimTest.App.<>c.<BuildRenderTree>b__0_1(RenderTreeBuilder): Field 'Microsoft.AspNetCore.Components.LayoutView.<Layout>k__BackingField' with 'DynamicallyAccessedMembersAttribute' is accessed via reflection. Trimmer can't guarantee availability of the requirements of the field. [~\BlazorTrimTest\BlazorTrimTest.csproj]

~\BlazorTrimTest\Pages\FetchData.razor(44,9): Trim analysis warning IL2026: BlazorTrimTest.Pages.FetchData.<OnInitializedAsync>d__2.MoveNext(): Using member 'System.Net.Http.Json.HttpClientJsonExtensions.GetFromJsonAsync<TValue>(HttpClient, String, CancellationToken)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. JSON serialization and deserialization might require types that cannot be statically analyzed. Use the overload that takes a JsonTypeInfo or JsonSerializerContext, or make sure all of the required types are preserved. [~\BlazorTrimTest\BlazorTrimTest.csproj]

ILLink : Trim analysis warning IL2118: BlazorTrimTest.App.BuildRenderTree(RenderTreeBuilder): Compiler-generated member 'Microsoft.AspNetCore.Components.Routing.Router.<RunOnNavigateAsync>d__61.path' is accessed via reflection. Trimmer can't guarantee availability of the requirements of the member. ~\BlazorTrimTest\BlazorTrimTest.csproj]

~...\.nuget\packages\microsoft.aspnetcore.components\7.0.0-rc.2.22476.2\lib\net7.0\Microsoft.AspNetCore.Components.dll : warning IL2104: Assembly 'Microsoft.AspNetCore.Components' produced trim warnings. For more information see https://aka.ms/dotnet-illink/libraries [~\BlazorTrimTest\BlazorTrimTest.csproj]

~...\.nuget\packages\microsoft.jsinterop\7.0.0-rc.2.22476.2\lib\net7.0\Microsoft.JSInterop.dll : warning IL2104: Assembly 'Microsoft.JSInterop' produced trim warnings. For more information see https://aka.ms/dotnet-illink/libraries [~\BlazorTrimTest\BlazorTrimTest.csproj]

.NET Version

7.0.100-rc.2.22477.23

Anything else?

Marginally related: #39839

[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.

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 8 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[Blackclaws]

Just ran into this issue. We wanted to find issues with trimming because the wasm app wasn't keeping some classes. The deluge of warnings is really irritating to work with.

[hjrb]

I agree. E.g. a simple HttpClient.GetFromJsonAsync triggers the warning
Severity Code Description Project File Line Suppression State
Warning IL2026 Using member 'System.Net.Http.Json.HttpClientJsonExtensions.GetFromJsonAsync(HttpClient, String, CancellationToken)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. JSON serialization and deserialization might require types that cannot be statically analyzed. Use the overload that takes a JsonTypeInfo or JsonSerializerContext, or make sure all of the required types are preserved. VSSApp.Client C:\Users\ret2fe\Projects\repos\hjrb\VSSApp\Client\Pages\AdminPage.razor.cs 49 N/A

That is all around.
Also for entity framework core: DbContext(DbContextOptions<...> options) - same!
This renders trimming kind of useless.

[Blackclaws]

I agree. E.g. a simple HttpClient.GetFromJsonAsync triggers the warning Severity Code Description Project File Line Suppression State Warning IL2026 Using member 'System.Net.Http.Json.HttpClientJsonExtensions.GetFromJsonAsync(HttpClient, String, CancellationToken)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. JSON serialization and deserialization might require types that cannot be statically analyzed. Use the overload that takes a JsonTypeInfo or JsonSerializerContext, or make sure all of the required types are preserved. VSSApp.Client C:\Users\ret2fe\Projects\repos\hjrb\VSSApp\Client\Pages\AdminPage.razor.cs 49 N/A

That is actually valuable feedback that makes sense as a warning. Because there is actually a way to use this functionality that preserves the correct type info as the warning states.

The issue really is with warnings that come from the generated code in Razor files I find.

[hjrb]

That is actually valuable feedback that makes sense as a warning. Because there is actually a way to use this functionality that preserves the correct type info as the warning states.
I don't know how. Do you?

[yugabe]

@hjrb, it is covered in the docs here.

This issue here is not about warnings about trimming in general - they are unarguably useful. It's about how there are already warnings in the default project without adding any custom code to it.

[hjrb]

Thanks for the link. But see: even as part of the Blazor WASM template there is such a call HttpClient.GetFromJsonAsync to get the Weather Data.

[yugabe]

Ah, I see. In that case sure, this is exactly what the issue is 😅
In fact, upon taking another look, I mention this exact one in the issue OP too.
The best case study is right here. The warnings are not straightforward to fix (usually), so the template itself should include them by default as is advised by the warning.

[hjrb]

The warnings are not straightforward to fix (usually), so the template itself should include them by default as is advised by the warning.
Exactly.

[hjrb]

I gave it a try with the method for JSON Serializer Code generation. That works OK as long as you use only trivial types. But as soon as you use nested types like IEnumerable it doesn't work right away. I didn't want to spend the effort to figure out how to make it work. That should be included in the templates - as requested. With a reasonable, non trivial example.

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 9 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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]

Thanks for contacting us.

We're moving this issue to the .NET 9 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.