Step 18 (part 7): Extensions — render components + SX escape

Two hyperscript extensions beyond stock:

render ~component :key val [into|before|after target]
  Tokenizer: ~ + ident → component token type
  Parser: render command with kwargs and optional position
  Compiler: emits (render-to-html ~comp :key val) or
            (hs-put! (render-to-html ...) pos target)
  Bridges hyperscript flow to SX component rendering

eval (sx-expression) — SX escape hatch
  Inside eval (...), content is SX syntax (not hyperscript)
  Parser: collect-sx-source extracts balanced parens from raw source
  Compiler: sx-parse at compile time, inlines AST directly
  Result: SX runs in handler scope — hyperscript variables visible!
  Also supports string form: eval '(+ 1 2)' for backward compat

  set name to "Giles"
  set greeting to eval (str "Hello " name)  -- name is visible!

16 new tests (parser + compiler + integration).
3127/3127 full build, zero regressions.

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

spec/tests/test-hyperscript-compiler.sx

@@ -203,6 +203,55 @@
       (assert= (quote fn) (first (nth sx 1))))))
 
 ;; ── Return and throw ─────────────────────────────────────────
+(defsuite
+  "hs-emit-render"
+  (deftest
+    "render emits render-to-html"
+    (let
+      ((sx (hs-to-sx-from-source "render ~card")))
+      (assert= (quote render-to-html) (first sx))
+      (assert= (quote ~card) (nth sx 1))))
+  (deftest
+    "render with kwargs emits keywords"
+    (let
+      ((sx (hs-to-sx-from-source "render ~card :title 'Hi'")))
+      (assert= (quote render-to-html) (first sx))
+      (assert= (quote ~card) (nth sx 1))
+      (assert= (make-keyword "title") (nth sx 2))
+      (assert= "Hi" (nth sx 3))))
+  (deftest
+    "render into emits hs-put!"
+    (let
+      ((sx (hs-to-sx-from-source "render ~card into #box")))
+      (assert= (quote hs-put!) (first sx))
+      (assert= (quote render-to-html) (first (nth sx 1)))
+      (assert= "into" (nth sx 2))))
+  (deftest
+    "component ref emits symbol"
+    (let
+      ((sx (hs-to-sx (list (quote component) "~badge"))))
+      (assert= (quote ~badge) sx))))
+
+;; ── Increment / decrement ────────────────────────────────────
+(defsuite
+  "hs-emit-sx-eval"
+  (deftest
+    "eval inlines SX at compile time"
+    (let
+      ((sx (hs-to-sx-from-source "set x to eval (+ 1 2)")))
+      (assert= (quote set!) (first sx))
+      (let
+        ((val (nth sx 2)))
+        (assert= (quote +) (first val))
+        (assert= 1 (nth val 1))
+        (assert= 2 (nth val 2)))))
+  (deftest
+    "eval preserves variable refs"
+    (let
+      ((sx (hs-to-sx-from-source "eval (log x)")))
+      (assert= (quote log) (first sx))
+      (assert= (quote x) (nth sx 1)))))
+
 (defsuite
   "hs-emit-return-throw"
   (deftest
@@ -227,7 +276,6 @@
       (assert= (quote hs-wait-for) (first sx))
       (assert= "transitionend" (nth sx 2)))))
 
-;; ── Increment / decrement ────────────────────────────────────
 (defsuite
   "hs-emit-inc-dec"
   (deftest

spec/tests/test-hyperscript-parser.sx

@@ -649,6 +649,64 @@
       (assert= "reset" (nth ast 1))
       (assert= 0 (len (nth ast 2))))))
 
+(defsuite
+  "hs-parse-render"
+  (deftest
+    "render component"
+    (let
+      ((ast (hs-compile "render ~card")))
+      (assert= (quote render) (first ast))
+      (assert= "~card" (nth ast 1))
+      (assert= 0 (len (nth ast 2)))))
+  (deftest
+    "render with kwargs"
+    (let
+      ((ast (hs-compile "render ~card :title 'Hello'")))
+      (assert= "~card" (nth ast 1))
+      (let
+        ((kw (nth ast 2)))
+        (assert= "title" (first kw))
+        (assert= "Hello" (nth kw 1)))))
+  (deftest
+    "render into target"
+    (let
+      ((ast (hs-compile "render ~card :title 'Hi' into #box")))
+      (assert= "into" (nth ast 3))
+      (assert= (quote query) (first (nth ast 4)))))
+  (deftest
+    "component token in expression"
+    (let
+      ((ast (hs-compile "set x to ~myComp")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote component) (first val))
+        (assert= "~myComp" (nth val 1))))))
+
+(defsuite
+  "hs-parse-sx-eval"
+  (deftest
+    "eval with parens extracts raw SX"
+    (let
+      ((ast (hs-compile "set x to eval (+ 1 2)")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote sx-eval) (first val))
+        (assert= "(+ 1 2)" (nth val 1)))))
+  (deftest
+    "eval with string fallback"
+    (let
+      ((ast (hs-compile "eval '(log 42)'")))
+      (assert= (quote sx-eval) (first ast))
+      (assert= "(log 42)" (nth ast 1))))
+  (deftest
+    "eval nested parens"
+    (let
+      ((ast (hs-compile "set x to eval (map (fn (x) (+ x 1)) items)")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote sx-eval) (first val))
+        (assert= "(map (fn (x) (+ x 1)) items)" (nth val 1))))))
+
 (defsuite
   "hs-parse-every-modifier"
   (deftest

spec/tests/test-hyperscript-runtime.sx

@@ -125,4 +125,22 @@
       ((sx (hs-to-sx-from-source "def add(a, b) return a end")))
       (assert= (quote define) (first sx))
       (assert= (quote add) (nth sx 1))
-      (assert= (quote fn) (first (nth sx 2))))))
+      (assert= (quote fn) (first (nth sx 2))))))
+
+(defsuite
+  "hs-handler-extensions"
+  (deftest
+    "render compiles to render-to-html"
+    (let
+      ((sx (hs-to-sx-from-source "render ~badge :label 'New'")))
+      (assert= (quote render-to-html) (first sx))
+      (assert= (quote ~badge) (nth sx 1))))
+  (deftest
+    "eval inlines SX with variable access"
+    (let
+      ((h (hs-handler "set x to 10 then set y to eval (+ x 5)")))
+      (h "el")
+      (assert= 15 y)))
+  (deftest
+    "eval as command in handler"
+    (let ((h (hs-handler "eval (set! z 99)"))) (h "el") (assert= 99 z))))