Serve a React index.html document (the ui.tsx pattern)

Reads a complete HTML document — the kind a Vite build emits — and injects the shinyreact page-level dependencies into it. The document must contain Shiny's dependency placeholder inside <head>:

Usage

page_react_html(
  path = "www/index.html",
  ...,
  extra_deps = NULL,
  shinyreact_js = "server"
)

Arguments

path: Path to the HTML document. Defaults to "www/index.html", relative to the working directory.
...: Ignored.
extra_deps: A list of additional htmltools::htmlDependency objects to render at the placeholder. A complete document has no tag tree to attach dependencies to, so this is the only way in — the counterpart of page_react()'s .... They render after Shiny's and shinyreact's, so they can rely on window.shinyreact existing. Mirrors Python's page_react_html(extra_deps=).
shinyreact_js: Who supplies shinyreact.js / shinyreact.css: "server" (the default) or "client" for an npm-tier app whose bundle imports @posit-dev/shinyreact — see page_react().

Value

UI suitable for shinyApp(ui = ...).

Details

<meta name="shiny-dependency-placeholder" content="">

Shiny's and shinyreact's script/link tags render in its place. It is an ordinary <meta> tag rather than template syntax, so the document stays valid HTML that a bundler's dev server can serve unchanged. Use as the ui argument: shinyApp(ui = page_react_html(), server = ...).

Assets the document references (your bundle's JS/CSS) should live in www/, where Shiny serves them statically.

For apps that don't need to own the HTML document, prefer page_react() — it requires no HTML file at all.

The whole document is a template

R places the dependencies with htmltools::htmlTemplate(), which evaluates every {{ ... }} in the document as R code — anywhere in it, <head> or <body>, with the global environment as parent. So a body containing {{ 6*7 }} renders 42, and {{ nonexistent() }} is an error at page render.

A document written for a JS templating engine that also uses {{ }} (Handlebars, Mustache, Vue's text interpolation) is therefore not safe to pass here as is — those braces will be evaluated as R. Escape them, or use page_react(), which needs no HTML file at all.

Python's page_react_html() differs: it replaces the placeholder and leaves the rest of the document untouched. Documented as a deliberate divergence rather than a bug — see FEATURES.md and issue #223.

Path resolution

A relative path resolves against the process working directory. Under shiny::runApp() / shiny::shinyApp() that is the app directory, so the default "www/index.html" just works. R has no per-caller __file__, so unlike Python — which resolves a relative path against the calling module's directory — there is nothing to resolve against outside the working directory. Pass an absolute path if you need to be independent of it.

The placeholder must be spelled exactly as above — the check is a fixed-string match, so a differently-quoted or reordered <meta> tag is rejected.