[release/9.0] [Blazor] Fix custom elements JS assets not being included in build output

[MackinnonBuck]

Fix custom elements JS assets not being included in build output

This update addresses an issue where JS assets providing functionality for the Microsoft.AspNetCore.Components.CustomElements package were not correctly built, causing the extension method RootComponentMappingCollection.RegisterCustomElement() to throw an exception.

Description

The MSBuild logic to include JS assets in the Microsoft.AspNetCore.Components.CustomElements package stopped working because the target that adds JS assets started running too late in the build process (after the ResolveJSModuleStaticWebAssets target). Although the reasons for the change in target ordering are unknown, the fix is to explicitly run the target before ResolveJSModuleStaticWebAssets.

This bug was discovered during the investigation of failures in our automated Blazor E2E tests.

Fixes #60859

Customer Impact

If this bug is left unfixed, calls to RegisterCustomElement() will throw an exception, preventing Blazor WebAssembly functionality from working. In a Blazor Web App, this may cause partial or complete loss of app functionality, and in Blazor WebAssembly apps, complete loss of app functionality.

However, note that this issue would only affect Blazor apps using the Microsoft.AspNetCore.Components.CustomElements package. The primary purpose of the package is to expose Blazor components as custom elements that can be rendered from a JavaScript-based UI library.

We don't have any customer data on the bug because a version of the package with the bug has not shipped. Version 9.0.3 would have included the bug, so we're going to skip shipping version 9.0.3 of this package and get this bug fixed for version 9.0.4.

Regression?

• Yes
• No

Regressed from Microsoft.AspNetCore.Components.CustomElements version 9.0.2.

Risk

• High
• Medium
• Low

The fix is simple and was applied back in October 2024 on the main branch.

Verification

• Manual (required)
• Automated

Automated E2E tests caught this bug an SDK update PR targeting main because the components-e2e pipeline is a required check in main. However, since that pipeline was not required for release branches, this issue slipped through the cracks for release/9.0. This has been fixed, and the components-e2e pipeline is now a required check for release branches.

Packaging Changes Reviewed?

• Yes
• No
• N/A

[Copilot]

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

[wtgodbe]

Approved over email