From ba3f40a3f0a04977a4bebc9868a0b877a1d99572 Mon Sep 17 00:00:00 2001
From: slhx agent <slhx@users.noreply.github.com>
Date: Tue, 26 May 2026 01:28:51 +0200
Subject: [PATCH] feat(build): emit checked param tokens

Generate ParamName constants for handle data parameters so public code can refer to checked param metadata instead of stringly typed names.

req: codegen/003
---
 slhx-build/src/lib.rs           | 18 ++++++++++++++++++
 slhx-core/src/lib.rs            | 29 +++++++++++++++++++++++++++++
 slhx-core/tests/effect_batch.rs | 10 +++++++++-
 slhx/src/lib.rs                 |  2 +-
 4 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/slhx-build/src/lib.rs b/slhx-build/src/lib.rs
index 83507ba..b19a664 100644
--- a/slhx-build/src/lib.rs
+++ b/slhx-build/src/lib.rs
@@ -425,6 +425,22 @@ impl Resources {
         ));
         out.push_str(&format!("{pad}}}\n\n"));
 
+        out.push_str(&format!("{pad}#[allow(non_upper_case_globals)]\n{pad}pub mod params {{\n"));
+        let mut emitted_params = BTreeSet::new();
+        for res in self.handles.values().filter(|res| component_matches(res, component)) {
+            if let Some(params) = self.handle_params.get(&res.ident) {
+                for param in params {
+                    if emitted_params.insert(param.as_str()) {
+                        out.push_str(&format!(
+                            "{inner}pub const {param}: ::slhx::ParamName = ::slhx::ParamName::new({});\n",
+                            rust_str(param)
+                        ));
+                    }
+                }
+            }
+        }
+        out.push_str(&format!("{pad}}}\n\n"));
+
         out.push_str(&format!("{pad}#[allow(non_upper_case_globals)]\n{pad}pub mod atoms {{\n"));
         for res in self.atoms.values().filter(|res| component_matches(res, component)) {
             out.push_str(&format!(
@@ -1076,6 +1092,8 @@ mod tests {
         assert!(generated.contains("pub const todos"));
         assert!(generated.contains("pub mod handles"));
         assert!(generated.contains("pub const create: ::slhx::Handle<::slhx::Form<::std::string::String>>"));
+        assert!(generated.contains("pub mod params"));
+        assert!(generated.contains("pub const todo_id: ::slhx::ParamName = ::slhx::ParamName::new(\"todo_id\")"));
         assert!(generated.contains("pub mod forms"));
         assert!(generated.contains("pub mod atoms"));
         assert!(generated.contains("pub const filter"));
diff --git a/slhx-core/src/lib.rs b/slhx-core/src/lib.rs
index ab7ccdd..4803c7b 100644
--- a/slhx-core/src/lib.rs
+++ b/slhx-core/src/lib.rs
@@ -186,6 +186,35 @@ impl core::fmt::Display for CssClass {
     }
 }
 
+/// A generated, checked parameter token.
+/// req: codegen/003
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub struct ParamName {
+    name: &'static str,
+}
+
+impl ParamName {
+    pub const fn new(name: &'static str) -> Self {
+        Self { name }
+    }
+
+    pub const fn as_str(self) -> &'static str {
+        self.name
+    }
+}
+
+impl AsRef<str> for ParamName {
+    fn as_ref(&self) -> &str {
+        self.name
+    }
+}
+
+impl core::fmt::Display for ParamName {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.name)
+    }
+}
+
 /// A generated, checked component token.
 /// req: component/003
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
diff --git a/slhx-core/tests/effect_batch.rs b/slhx-core/tests/effect_batch.rs
index 865347f..ec30e2f 100644
--- a/slhx-core/tests/effect_batch.rs
+++ b/slhx-core/tests/effect_batch.rs
@@ -1,7 +1,7 @@
 use slhx_core::{
     event, navigate, redirect, replace, Atom, AtomSnapshot, AtomState, BuildFingerprint,
     ComponentRef, CssClass, CssClasses, Effect, EffectBatch, Form, Handle, IntoEffect, KeyedSlot,
-    NavigateMode, Payload, ResourceKind, SafeHtml, ScopeKey, Slot,
+    NavigateMode, ParamName, Payload, ResourceKind, SafeHtml, ScopeKey, Slot,
 };
 
 #[test]
@@ -93,6 +93,14 @@ fn slot_html_requires_explicit_safe_html() {
     assert_eq!(payload, Payload::Html(String::from("<strong>ok</strong>")));
 }
 
+#[test]
+fn param_names_format_generated_param_names() {
+    // req: codegen/003
+    let param = ParamName::new("todo_id");
+    assert_eq!(param.as_str(), "todo_id");
+    assert_eq!(param.to_string(), "todo_id");
+}
+
 #[test]
 fn component_refs_format_generated_component_names() {
     // req: component/003
diff --git a/slhx/src/lib.rs b/slhx/src/lib.rs
index 71dffa9..ae019f2 100644
--- a/slhx/src/lib.rs
+++ b/slhx/src/lib.rs
@@ -50,7 +50,7 @@ pub mod prelude {
     pub use slhx_core::{
         navigate, push, redirect, replace, Atom, BuildFingerprint, ComponentRef, CssClass,
         CssClasses, Effect, EventName, Form, FormModel, FormValue, Handle, IntoEffect, KeyedSlot,
-        Slot,
+        ParamName, Slot,
     };
     pub use crate::{render_html, RenderKeyedSlotExt, RenderSlotExt};
     pub use slhx_derive::{app, component, form, handler, surface};