Blazor messes up standard HTMLTemplateElement <template>

[Vinoth2562000]

Blazor messes up standard HTMLTemplateElement <template>

Description

When content was rendered inside a <template> tag (for example, through a RenderFragment), Blazor appended child nodes directly to the <template> element instead of its associated content DocumentFragment. This behavior was not compliant with the HTML specification for HTMLTemplateElement, which requires all child content to be stored within template.content while the <template> element itself remains empty.

To address this, the rendering logic in LogicalElements has been updated to recognize HTMLTemplateElement instances and correctly insert rendered content into the element's content DocumentFragment. This ensures that the generated DOM structure aligns with native browser behavior and the HTML specification.

Before

After

Changes included

• Updated appendDomNode in LogicalElements.ts to route DOM insertions through a container-resolution helper.
• Added an internal getLogicalDomNodeContainer(parent) helper that resolves the correct DOM container for logical element operations:
  • Returns template.content for HTMLTemplateElement instances.
  • Returns the element itself for all other element types.
• Added comprehensive test coverage for HTMLTemplateElement handling in LogicalElements.test.ts.

Fixes #50831

[dotnet-policy-service]

Thanks for your PR, @Vinoth2562000. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.