M6: default Vue instance swaps and keep text out of attribute detection

A Vue component's instance-swap prop now defaults to its component reference in withDefaults, so the dynamic component renders the design default. Attribute detection only applies inside an unfinished opening tag, so text like `Total = {title}` stays text instead of becoming a quoted attribute value.

crates/engine/src/code_connect.rs

@@ -184,10 +184,38 @@ fn expr(doc: &Document, c: &Component, p: &Param, v: &Value, lang: CodeLang) ->
     }
 }
 
+/// Whether `s` ends inside an unclosed opening tag (no `>` outside quotes since the last `<`).
+fn inside_open_tag(s: &str) -> bool {
+    let mut in_tag = false;
+    let mut quote = None;
+    let mut chars = s.chars().peekable();
+    while let Some(c) = chars.next() {
+        match quote {
+            Some(q) => {
+                if c == q {
+                    quote = None;
+                }
+            }
+            None => match c {
+                '<' if !in_tag && chars.peek().is_some_and(|ch| ch.is_ascii_alphabetic() || matches!(*ch, '/' | '!' | '?')) => {
+                    in_tag = true;
+                }
+                '>' if in_tag => in_tag = false,
+                '"' | '\'' if in_tag => quote = Some(c),
+                _ => {}
+            },
+        }
+    }
+    in_tag
+}
+
 /// Where a placeholder sits in a Vue template: whether the attribute is bound, and the quote the
 /// template already opened (if any). `None` when it isn't in an attribute at all.
 fn vue_attribute(out: &str) -> Option<(bool, Option<char>)> {
     let end = out.trim_end();
+    if !inside_open_tag(end) {
+        return None;
+    }
     let (after, quote) = match end.chars().last() {
         Some(q @ ('"' | '\'')) => (&end[..end.len() - q.len_utf8()], Some(q)),
         _ => (end, None),

crates/engine/src/code_connect_tests.rs

@@ -237,6 +237,10 @@ fn vue_links_are_a_default_import_with_quoted_bindings() {
     ex(&mut s, "instance.setProperties", json!({"ids": [i], "properties": {"Title": "Say \"hi\""}}));
     ex(&mut s, "codeConnect.set", json!({"id": i, "language": "vue", "template": "<Card title=\"{title} {title}\" />"}));
     assert_eq!(code(&mut s, i, "vue"), "import Card from \"./Card.vue\";\n\n<Card title=\"Say &quot;hi&quot; Say &quot;hi&quot;\" />\n");
+    // Text after a completed tag is text, even when it contains `=`.
+    ex(&mut s, "instance.setProperties", json!({"ids": [i], "properties": {"Title": "Buy"}}));
+    ex(&mut s, "codeConnect.set", json!({"id": i, "language": "vue", "template": "<p>Total = {title}</p>"}));
+    assert_eq!(code(&mut s, i, "vue"), "import Card from \"./Card.vue\";\n\n<p>Total = Buy</p>\n");
     // Vue is linkable; a language that isn't stays refused.
     assert!(s.execute("codeConnect.set", &json!({"id": c, "language": "css"})).is_err(), "not a code language");
     assert!(s.execute("codeConnect.set", &json!({"id": c, "language": "vue", "importPath": "a b"})).is_err(), "no spaces in a path");

crates/engine/src/component_codegen.rs

@@ -823,10 +823,7 @@ fn vue(doc: &Document, c: &Component) -> String {
         }
         out.push_str("  }>(),\n  {\n");
         for p in &props {
-            // A component-valued prop has no literal to default to.
-            if matches!(p.kind, ParamKind::InstanceSwap | ParamKind::Slot) {
-                continue;
-            }
+            // An instance swap defaults to its component reference; a slot isn't in `props`.
             out.push_str(&format!("    {}: {},\n", p.ident, value_expr(doc, c, p, &p.default, CodeLang::Vue)));
         }
         out.push_str("  },\n);\n\n</script>\n\n");

crates/engine/src/component_codegen_tests.rs

@@ -228,6 +228,7 @@ fn instance_swap_properties_take_views() {
     assert!(leptos.contains("{icon.run()}"), "{leptos}");
     let vue = code(&mut s, chip, "vue");
     assert!(vue.contains("    icon?: unknown;"), "{vue}");
+    assert!(vue.contains("    icon: HeartIcon,"), "the swap defaults to its component: {vue}");
     assert!(vue.contains("<component :is=\"icon\" />"), "a swap is a component, not an element: {vue}");
     let i = idv(&ex(&mut s, "instance.create", json!({"component": chip, "x": 0, "y": 100})));
     ex(&mut s, "instance.setProperties", json!({"ids": [i], "properties": {"Icon": star}}));