Step 18 (part 6): _hyperscript integration — _="..." attribute wiring

lib/hyperscript/integration.sx — connects compiled hyperscript to DOM:
  hs-handler(src) — compile source → callable (fn (me) ...) via eval-expr-cek
  hs-activate!(el) — read _="...", compile, execute with me=element
  hs-boot!() — scan document for [_] elements, activate all
  hs-boot-subtree!(root) — activate within subtree (for HTMX swaps)

Handler wraps compiled SX in (fn (me) (let ((it nil) (event nil)) ...))
so each element gets its own me binding and clean it/event state.
Double-activation prevented via data-hs-active marker.

12 integration tests verify full pipeline: source → compile → eval.
Handlers correctly bind me, support arithmetic, conditionals, sequences,
for loops, and repeat. 3111/3111 full build, zero regressions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/bin/run_tests.ml

@@ -1313,6 +1313,7 @@ let run_spec_tests env test_files =
   load_module "parser.sx" hs_dir;
   load_module "compiler.sx" hs_dir;
   load_module "runtime.sx" hs_dir;
+  load_module "integration.sx" hs_dir;
   load_module "types.sx" lib_dir;
   load_module "sx-swap.sx" lib_dir;
   (* Shared templates: TW styling engine *)

lib/hyperscript/integration.sx

@@ -0,0 +1,66 @@
+;; _hyperscript integration — wire _="..." attributes to compiled SX
+;;
+;; Entry points:
+;;   (hs-handler src)       — compile source to callable (fn (me) ...)
+;;   (hs-activate! el)      — activate hyperscript on a single element
+;;   (hs-boot!)             — scan DOM, activate all _="..." elements
+;;   (hs-boot-subtree! root) — activate within a subtree (for HTMX swaps)
+
+;; ── Compile source to a handler function ────────────────────────
+;; Returns a function (fn (me) ...) that can be called with a DOM element.
+;; Uses eval-expr-cek to turn the SX data structure into a live closure.
+
+(define
+  hs-handler
+  (fn
+    (src)
+    (let
+      ((sx (hs-to-sx-from-source src)))
+      (eval-expr-cek
+        (list
+          (quote fn)
+          (list (quote me))
+          (list
+            (quote let)
+            (list (list (quote it) nil) (list (quote event) nil))
+            sx))))))
+
+;; ── Activate a single element ───────────────────────────────────
+;; Reads the _="..." attribute, compiles, and executes with me=element.
+;; Marks the element to avoid double-activation.
+
+(define
+  hs-activate!
+  (fn
+    (el)
+    (let
+      ((src (dom-get-attr el "_")))
+      (when
+        (and src (not (dom-get-data el "hs-active")))
+        (dom-set-data el "hs-active" true)
+        (let ((handler (hs-handler src))) (handler el))))))
+
+;; ── Boot: scan entire document ──────────────────────────────────
+;; Called once at page load. Finds all elements with _ attribute,
+;; compiles their hyperscript, and activates them.
+
+(define
+  hs-boot!
+  (fn
+    ()
+    (let
+      ((elements (dom-query-all (dom-body) "[_]")))
+      (for-each (fn (el) (hs-activate! el)) elements))))
+
+;; ── Boot subtree: for dynamic content ───────────────────────────
+;; Called after HTMX swaps or dynamic DOM insertion.
+;; Only activates elements within the given root.
+
+(define
+  hs-boot-subtree!
+  (fn
+    (root)
+    (let
+      ((elements (dom-query-all root "[_]")))
+      (for-each (fn (el) (hs-activate! el)) elements))
+    (when (dom-get-attr root "_") (hs-activate! root))))

spec/tests/test-hyperscript-integration.sx

@@ -0,0 +1,76 @@
+;; _hyperscript integration tests
+;; Tests hs-handler: source → callable function via eval-expr-cek.
+;; DOM-dependent tests (hs-boot!, hs-activate!) deferred to Playwright.
+
+;; ── Handler compilation ───────────────────────────────────────
+(defsuite
+  "hs-handler-compilation"
+  (deftest
+    "handler returns a function"
+    (let ((h (hs-handler "log 'hello'"))) (assert= true (procedure? h))))
+  (deftest
+    "handler accepts me argument"
+    (let
+      ((h (hs-handler "set x to 42")))
+      (h "mock-element")
+      (assert= 42 x)))
+  (deftest
+    "handler can return a value"
+    (let ((h (hs-handler "return 99"))) (assert= 99 (h "el"))))
+  (deftest
+    "handler binds me from argument"
+    (let
+      ((h (hs-handler "set x to me")))
+      (h "my-element")
+      (assert= "my-element" x)))
+  (deftest
+    "handler initializes it to nil"
+    (let ((h (hs-handler "set x to it"))) (h "el") (assert= nil x))))
+
+;; ── Arithmetic in handler ─────────────────────────────────────
+(defsuite
+  "hs-handler-expressions"
+  (deftest
+    "arithmetic works in handler"
+    (let ((h (hs-handler "set x to 2 + 3"))) (h "el") (assert= 5 x)))
+  (deftest
+    "string concatenation via set"
+    (let
+      ((h (hs-handler "set x to 'hello'")))
+      (h "el")
+      (assert= "hello" x)))
+  (deftest
+    "conditional in handler"
+    (let
+      ((h (hs-handler "if true set x to 1 end")))
+      (h "el")
+      (assert= 1 x)))
+  (deftest
+    "if-else in handler"
+    (let
+      ((h (hs-handler "if false set x to 1 else set x to 2 end")))
+      (h "el")
+      (assert= 2 x))))
+
+;; ── Sequence / control flow ───────────────────────────────────
+(defsuite
+  "hs-handler-control"
+  (deftest
+    "then chains commands"
+    (let
+      ((h (hs-handler "set x to 1 then set y to 2")))
+      (h "el")
+      (assert= 1 x)
+      (assert= 2 y)))
+  (deftest
+    "for iterates"
+    (let
+      ((h (hs-handler "set total to 0 then for n in [1, 2, 3] set total to total + n end")))
+      (h "el")
+      (assert= 6 total)))
+  (deftest
+    "repeat counts"
+    (let
+      ((h (hs-handler "set count to 0 then repeat 3 times set count to count + 1 end")))
+      (h "el")
+      (assert= 3 count))))