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[Blazor] Use DynamicDependency to preserve KeyValuePair for WebAssembly trimming #63099

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[Blazor] Use DynamicDependency to preserve KeyValuePair for WebAssembly trimming #63099

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@Copilot Copilot AI commented Aug 4, 2025 •
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This change preserves System.Collections.Generic.KeyValuePair<TKey, TValue> during trimming to prevent runtime serialization issues in Blazor WebAssembly JS interop scenarios.

Problem

When Blazor WebAssembly applications are trimmed, the linker may remove types that are used during runtime serialization for JS interop calls, particularly System.Collections.Generic.KeyValuePair<TKey, TValue> which is commonly used in dictionary serialization scenarios.

Solution

Added a DynamicDependency attribute to the ReadJsonSerializerOptions() method to preserve only the public constructors of the KeyValuePair<,> type:

[DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(KeyValuePair<,>))]
public JsonSerializerOptions ReadJsonSerializerOptions() => JsonSerializerOptions;

This approach:

  • Is more specific than preserving all members - only preserves public constructors needed for serialization
  • Uses typeof(KeyValuePair<,>) for better type safety instead of hardcoded strings
  • Is co-located with the JSON serialization setup for better maintainability
  • Aligns with existing patterns in the WebAssembly project that already use DynamicDependency extensively
  • Is the modern approach recommended for .NET trimming scenarios

Changes

  • Modified: src/Components/WebAssembly/WebAssembly/src/Services/DefaultWebAssemblyJSRuntime.cs - Added DynamicDependency attribute to preserve KeyValuePair public constructors

This ensures that applications using the Components.WebAssembly package will automatically have these commonly needed types preserved during trimming without requiring developers to manually configure linker settings.

Fixes #63098.

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@Copilot Copilot AI changed the title [WIP] [Blazor] Add default IILink.Descriptors.xml to Components.WebAssembly [Blazor] Add default ILLink.Descriptors.xml to Components.WebAssembly Aug 4, 2025
@Copilot Copilot AI requested a review from javiercn August 4, 2025 13:31
Copilot finished work on behalf of javiercn August 4, 2025 13:31
@build-analysis build-analysis bot mentioned this pull request Aug 4, 2025
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@javiercn javiercn marked this pull request as ready for review August 4, 2025 18:44
@Copilot Copilot AI review requested due to automatic review settings August 4, 2025 18:44
@javiercn javiercn requested a review from a team as a code owner August 4, 2025 18:44
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Pull Request Overview

This PR adds a default ILLink.Descriptors.xml file to the Microsoft.AspNetCore.Components.WebAssembly project to prevent the linker from trimming commonly used types during serialization in JS interop scenarios, specifically addressing issues with KeyValuePair<TKey, TValue> being removed during WebAssembly trimming.

  • Added ILLink.Descriptors.xml file to preserve System.Collections.Generic.KeyValuePair<,> type during linking
  • Updated project file to embed the descriptors file as a resource
  • Provides automatic protection for common serialization scenarios without requiring manual developer configuration

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File Description
Microsoft.AspNetCore.Components.WebAssembly.csproj Added EmbeddedResource entry to include the ILLink descriptors file
ILLink.Descriptors.xml New linker descriptor file that preserves KeyValuePair types from trimming

@akoeplinger
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why can't we use DynamicDependency for this?

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Copilot AI commented Aug 4, 2025

why can't we use DynamicDependency for this?

You're absolutely right! I've updated the implementation to use DynamicDependency instead of ILLink.Descriptors.xml. The DynamicDependency attribute is more appropriate here since it's more explicit, ties the preservation to the actual JSON serialization setup, and aligns with the existing patterns in the WebAssembly project.

The attribute is now applied to the DefaultWebAssemblyJSRuntime constructor where JSON serialization is configured, which is the logical place for this dependency. This approach is more maintainable and follows the modern .NET trimming best practices.

Commit: fc94643

@Copilot Copilot AI changed the title [Blazor] Add default ILLink.Descriptors.xml to Components.WebAssembly [Blazor] Use DynamicDependency to preserve KeyValuePair for WebAssembly trimming Aug 4, 2025
@Copilot Copilot AI requested a review from akoeplinger August 4, 2025 19:06
Copilot finished work on behalf of akoeplinger August 4, 2025 19:06
Copilot finished work on behalf of pavelsavara August 4, 2025 19:23
@Copilot Copilot AI requested a review from pavelsavara August 4, 2025 19:23
@Copilot Copilot AI requested a review from pavelsavara August 4, 2025 19:34
Copilot finished work on behalf of pavelsavara August 4, 2025 19:34
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javiercn commented Aug 4, 2025 •
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why can't we use DynamicDependency for this?

Because we are preserving it for user's apps (this gets trimmed when they only use it through JSON serialization) and I feel it's cleaner to use the descriptor rather than dump a file we don't use and add DynamicDependency to it.

NVM, I saw that we are already putting some of these things on the JS runtime

javiercn
javiercn reviewed Aug 4, 2025
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src/Components/WebAssembly/WebAssembly/src/Services/DefaultWebAssemblyJSRuntime.cs Outdated
@@ -37,6 +37,7 @@ private DefaultWebAssemblyJSRuntime()
JsonSerializerOptions.Converters.Add(new ElementReferenceJsonConverter(ElementReferenceContext));
}

[DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(KeyValuePair<,>))]
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Move this to private DefaultWebAssemblyJSRuntime() instead.

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Moved the DynamicDependency attribute to the private constructor to consolidate all dynamic dependencies in one place. Commit: ba95337

@Copilot Copilot AI requested a review from javiercn August 4, 2025 20:41
Copilot finished work on behalf of javiercn August 4, 2025 20:41
@build-analysis build-analysis bot mentioned this pull request Aug 5, 2025
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Update src/Components/WebAssembly/WebAssembly/src/Microsoft.AspNetCor…
4c78ccd 
…e.Components.WebAssembly.csproj


Remove empty lines
@pavelsavara
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It would be good to cover this with some E2E unit test. It should be configured to trim and validate that JSON can be de-serialized into a dictionary. The test project should not make reference to KeyValuePair directly.

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javiercn commented Aug 5, 2025

It would be good to cover this with some E2E unit test. It should be configured to trim and validate that JSON can be de-serialized into a dictionary. The test project should not make reference to KeyValuePair directly.

I don't feel that's necessary, at that point we are testing the linker behavior and adding an E2E test adds significant overhead to the codebase and the CI runs.

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javiercn reviewed Aug 5, 2025
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src/Components/WebAssembly/WebAssembly/src/Services/DefaultWebAssemblyJSRuntime.cs
@@ -31,6 +31,7 @@ internal sealed partial class DefaultWebAssemblyJSRuntime : WebAssemblyJSRuntime
[DynamicDependency(nameof(BeginInvokeDotNet))]
[DynamicDependency(nameof(ReceiveByteArrayFromJS))]
[DynamicDependency(nameof(UpdateRootComponentsCore))]
[DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(KeyValuePair<,>))]
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@copilot Use LinkerFlags.JsonSerialized

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[Blazor] Add default IILink.Descriptors.xml to Components.WebAssembly
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