Blazor Components

Requirement A component MUST NOT call a browser API, read persisted state directly, or contain a business rule.

Rationale A rule deciding whether an action is allowed belongs in Domain or Application, where a test can reach it without rendering.

Requirement A component parameter MUST declare a concrete type owned by its feature.

Rationale A loosely typed bag of values hides the contract, and a Domain aggregate crossing into a component couples rendering to the core model. This realizes litespec/frontend/components#keep-component-inputs-narrow.

Requirement A child component MUST report upward through EventCallback rather than mutate a parent-owned object.

Rationale Writing to a shared store to signal a parent hides the relationship that the callback makes visible.

Requirement A feature view model MUST expose no Domain aggregate, Domain closed set, or Application result record.

Rationale Each layer mirrors the shape it needs, as litespec/backend/architecture#own-each-layers-contract-types requires. Shared-kernel typed identifiers and value objects are the one sanctioned crossing.

This rule and litespec/frontend/blazor/structure#keep-domain-free-of-browser-concerns guard the same boundary from opposite sides. That rule keeps browser types out of Domain. This rule keeps Domain types out of the view. Neither implies the other, because a view model can name an aggregate without Domain naming a component.

Requirement A component MUST resolve browser behavior through an Application-owned interface rather than inject the interop runtime.

Rationale The component then renders in a test with no JavaScript host.

Requirement A .razor file MUST declare one routable or reusable component named for what it renders.

Rationale Bundling components by kind hides each one. A component with more than trivial logic uses a code-behind partial class rather than a large inline block.

Requirement A component MUST own focus management, keyboard interaction, labeling, and live-region announcements for its interaction.

Rationale A page that composes the component cannot know which element should receive focus. This realizes litespec/frontend/components#support-keyboard-focus-labels-and-announcements.