HS: fix as Values SELECT + multi-select programmatic changes

- hs-value-of-node: use selectedIndex fallback when SELECT.value is
  empty (mock DOM doesn't auto-compute it from selected options)
- generate-sx-tests: manual body for 'programmatically changed
  selections' test — deselect dog, select cat before reading values

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/runtime.sx

@@ -1180,7 +1180,17 @@
           (if
             (host-get node "multiple")
             (hs-select-multi-values node)
-            (host-get node "value")))
+            (let
+              ((idx (host-get node "selectedIndex"))
+                (opts (host-get node "options"))
+                (raw-val (host-get node "value")))
+              (if
+                (and (not (nil? raw-val)) (not (= raw-val "")))
+                raw-val
+                (if
+                  (and (not (nil? opts)) (>= idx 0))
+                  (host-get (if (list? opts) (nth opts idx) (host-get opts idx)) "value")
+                  "")))))
         ((or (= typ "checkbox") (= typ "radio"))
           (if (host-get node "checked") (host-get node "value") nil))
         (true (host-get node "value"))))))

shared/static/wasm/sx/hs-runtime.sx

@@ -1180,7 +1180,17 @@
           (if
             (host-get node "multiple")
             (hs-select-multi-values node)
-            (host-get node "value")))
+            (let
+              ((idx (host-get node "selectedIndex"))
+                (opts (host-get node "options"))
+                (raw-val (host-get node "value")))
+              (if
+                (and (not (nil? raw-val)) (not (= raw-val "")))
+                raw-val
+                (if
+                  (and (not (nil? opts)) (>= idx 0))
+                  (host-get (if (list? opts) (nth opts idx) (host-get opts idx)) "value")
+                  "")))))
         ((or (= typ "checkbox") (= typ "radio"))
           (if (host-get node "checked") (host-get node "value") nil))
         (true (host-get node "value"))))))

spec/tests/test-hyperscript-behavioral.sx

@@ -3817,11 +3817,15 @@
   )
   (deftest "converts multiple selects with programmatically changed selections"
     (let ((_node (dom-create-element "form")))
-      (dom-set-inner-html _node "<select name=\"animal\" multiple> <option value=\"dog\" selected>Doggo</option> <option value=\"cat\">Kitteh</option> <option value=\"raccoon\" selected>Trash Panda</option> <option value=\"possum\">Sleepy Boi</option> </select>")
-      (let ((_result (eval-hs-locals "x as Values" (list (list (quote x) _node)))))
-        (assert= (nth (host-get _result "animal") 0) "cat")
-        (assert= (nth (host-get _result "animal") 1) "raccoon")
-      ))
+      (dom-set-inner-html _node "<select name="animal" multiple> <option value="dog" selected>Doggo</option> <option value="cat">Kitteh</option> <option value="raccoon" selected>Trash Panda</option> <option value="possum">Sleepy Boi</option> </select>")
+      (let ((_sel (dom-query _node "select")))
+        (let ((_opts (host-get _sel "options")))
+          (host-set! (nth _opts 0) "selected" false)
+          (host-set! (nth _opts 1) "selected" true)
+          (let ((_result (eval-hs-locals "x as Values" (list (list (quote x) _node)))))
+            (assert= (nth (host-get _result "animal") 0) "cat")
+            (assert= (nth (host-get _result "animal") 1) "raccoon")
+          ))))
   )
   (deftest "converts nested array as Flat"
     (assert= (eval-hs "[[1,2],[3,4]] as Flat") (list 1 2 3 4))

tests/playwright/generate-sx-tests.py

@@ -128,6 +128,18 @@ SKIP_TEST_NAMES = {
 # Manually-written SX test bodies for tests whose upstream body cannot be
 # auto-translated. Key = test name; value = SX lines to emit inside deftest.
 MANUAL_TEST_BODIES = {
+    "converts multiple selects with programmatically changed selections": [
+        '    (let ((_node (dom-create-element "form")))',
+        '      (dom-set-inner-html _node "<select name=\"animal\" multiple> <option value=\"dog\" selected>Doggo</option> <option value=\"cat\">Kitteh</option> <option value=\"raccoon\" selected>Trash Panda</option> <option value=\"possum\">Sleepy Boi</option> </select>")',
+        '      (let ((_sel (dom-query _node "select")))',
+        '        (let ((_opts (host-get _sel "options")))',
+        '          (host-set! (nth _opts 0) "selected" false)',
+        '          (host-set! (nth _opts 1) "selected" true)',
+        '          (let ((_result (eval-hs-locals "x as Values" (list (list (quote x) _node)))))',
+        '            (assert= (nth (host-get _result "animal") 0) "cat")',
+        '            (assert= (nth (host-get _result "animal") 1) "raccoon")',
+        '          ))))',
+    ],
     "iterate cookies values work": [
         '    (hs-cleanup!)',
         '    (host-set! (host-global "cookies") "foo" "bar")',