host: Phase 5.1 — interactive SX-page render from a handler, 181/181

KERNEL: add a render-page primitive (sx_server.ml, persistent mode) that renders
an UNEVALUATED SX expression with the server env via sx_render_to_html.
render-to-html expands defcomp components and collects keyword attrs itself; SX
handlers can't reach the server env, so the prim supplies it. Fixes the attr
mangling — bare render-to-html on an EVALUATED component tree turns (form :id ..)
into <form>idpost-new-form..; rendering the unevaluated expr keeps :id an attr.

HOST: lib/host/page.sx — host/page (expr -> HTML response) + host/page-route
(mount on a GET path). New page suite (8 tests) proves a generic attributed +
nested component renders correctly through a host route; verified ~editor/form
renders right too. This is the component-render step of the generic
interactive-SX-page capability; shell + static assets + hydration (5.2-5.4) next.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/host/conformance.sh

@@ -76,6 +76,7 @@ MODULES=(
   "lib/host/feed.sx"
   "lib/host/relations.sx"
   "lib/host/blog.sx"
+  "lib/host/page.sx"
   "lib/host/server.sx"
   "lib/host/ledger.sx"
 )
@@ -89,6 +90,7 @@ SUITES=(
   "feed        host-fd-tests-run!  lib/host/tests/feed.sx"
   "relations   host-rl-tests-run!  lib/host/tests/relations.sx"
   "blog        host-bl-tests-run!  lib/host/tests/blog.sx"
+  "page        host-pg-tests-run!  lib/host/tests/page.sx"
   "server      host-sv-tests-run!  lib/host/tests/server.sx"
   "ledger      host-lg-tests-run!  lib/host/tests/ledger.sx"
 )

lib/host/page.sx

@@ -0,0 +1,22 @@
+;; lib/host/page.sx — serve interactive SX component/island pages on the host
+;; (Phase 5: the generic interactive-SX-page capability).
+;;
+;; The bare `render-to-html` path mangles an EVALUATED component tree's keyword
+;; attributes ((form :id ..) -> "<form>idpost-new-form..."), because evaluating a
+;; defcomp body turns `:id` into a child. The kernel `render-page` primitive
+;; instead renders an UNEVALUATED expression with the server env: render-to-html
+;; expands the components itself and collects keyword args as attributes. SX
+;; handlers can't reach the server env, so render-page supplies it.
+;;
+;; host/page wraps a rendered expression as an HTML response; host/page-route
+;; mounts it on a GET path. This is the component-render step (5.1); the full page
+;; shell (inlined component defs + CSS + client runtime + hydration) and static
+;; asset serving (5.2–5.4) build on top to make the page interactive.
+;; Depends on the kernel `render-page` primitive + lib/dream/types.sx (dream-html).
+
+;; Render an unevaluated SX page/component expression to an HTML response.
+(define host/page (fn (expr) (dream-html (render-page expr))))
+
+;; Mount a GET route that renders a fixed page expression.
+(define host/page-route
+  (fn (path expr) (dream-get path (fn (req) (host/page expr)))))

lib/host/tests/page.sx

@@ -0,0 +1,60 @@
+;; lib/host/tests/page.sx — the host's interactive-SX-page capability (Phase 5.1).
+;; A defcomp component tree (with keyword attributes + nesting) renders to correct
+;; HTML through host/page / render-page, served by a host route. This is the
+;; capability the legacy editor (and any future island UI) needs — proven on a
+;; small component so it's not editor-specific.
+
+(define host-pg-pass 0)
+(define host-pg-fail 0)
+(define host-pg-fails (list))
+(define
+  host-pg-test
+  (fn (name actual expected)
+    (if (= actual expected)
+      (set! host-pg-pass (+ host-pg-pass 1))
+      (begin
+        (set! host-pg-fail (+ host-pg-fail 1))
+        (append! host-pg-fails {:name name :actual actual :expected expected})))))
+
+;; A component with keyword attributes (the case bare render-to-html mangles) and
+;; a nested component (expansion must recurse).
+(defcomp ~pg-badge (&key (label :as string))
+  (span :class "badge" :data-kind "tag" label))
+(defcomp ~pg-card (&key (title :as string))
+  (div :class "card"
+    (h2 :class "card-title" title)
+    (~pg-badge :label "new")))
+
+(define host-pg-req (fn (target) (dream-request "GET" target {} "")))
+(define host-pg-app
+  (host/make-app (list (list (host/page-route "/card" (quote (~pg-card :title "Hello")))))))
+
+(define host-pg-body (dream-resp-body (host-pg-app (host-pg-req "/card"))))
+
+(host-pg-test "page 200"
+  (dream-status (host-pg-app (host-pg-req "/card"))) 200)
+(host-pg-test "page is html"
+  (contains? (dream-resp-header (host-pg-app (host-pg-req "/card")) "content-type") "text/html")
+  true)
+;; attributes survive (the whole point) — class on the outer div
+(host-pg-test "outer div class attr"
+  (contains? host-pg-body "class=\"card\"") true)
+;; nested component expanded + its attrs survive
+(host-pg-test "nested component expanded"
+  (contains? host-pg-body "class=\"badge\"") true)
+(host-pg-test "nested data attr"
+  (contains? host-pg-body "data-kind=\"tag\"") true)
+;; keyword param values rendered as text content, not attrs
+(host-pg-test "title text rendered"
+  (contains? host-pg-body "Hello") true)
+(host-pg-test "badge label text rendered"
+  (contains? host-pg-body ">new<") true)
+;; NOT mangled — the keyword ":class" must not leak as text content
+(host-pg-test "no mangled keyword text"
+  (contains? host-pg-body ">classcard") false)
+
+(define
+  host-pg-tests-run!
+  (fn ()
+    {:total (+ host-pg-pass host-pg-fail)
+     :passed host-pg-pass :failed host-pg-fail :fails host-pg-fails}))