feat(web-components): add SSR support via Declarative Shadow DOM modules#36247
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Previous Behavior
@fluentui/web-componentshad no server-side rendering path. Components were defined and rendered only on the client, so SSR frameworks could not pre-render Fluent web components into HTML and hydrate them on load.The e2e tests ran against a custom harness that only covered client-side rendering.
New Behavior
@fluentui/web-componentsnow supports SSR via Declarative Shadow DOM, built on@microsoft/fast-elementand@microsoft/fast-html. Every component in the package ships a paireddefine-async.ts/*.definition-async.tsmodule so its template can render on the server and hydrate on the client.The build also emits two new asset types alongside the JS modules, one pair per component (42 of each), exposed through new package subpath exports:
@fluentui/web-components/<component>/template.html: declarative HTML template wrapped in<f-template>, consumed by@microsoft/fast-htmlto render Declarative Shadow DOM on the server.@fluentui/web-components/<component>/styles.css: plain CSS extracted from the component's styles, importable as a raw stylesheet without pulling in the component's JS.Currently, the SSR templates and styles are generated at build time and placed in the
distoutput, but we may want to provide them as src assets in the future for easier consumption and customization.New test harness modules (
test/src/entry-client.ts,test/src/entry-server.ts) and atest/ssr.htmlentry point template exercise the DSD output end-to-end. The e2e pipeline runs SSR tests after CSR tests.Several components needed template or base adjustments to render correctly under SSR: tooltip (anchor positioning polyfill handling), text-input, textarea, tree, and tree-item. The
theme/set-themetests are skipped under SSR.Next Steps
This PR lays the groundwork for SSR support in
@fluentui/web-components, but there are still some follow-up tasks to complete:@microsoft/fast-elementand remove the@microsoft/fast-htmldependency, as DSD rendering will be directly supported in FAST in the next major release.