fix: build Path<Struct> parameters from fields(), not scraped properties

gotcha/tests/test_path_params.rs

@@ -48,6 +48,58 @@ fn test_path_tuple_parameter() {
     }
 }
 
+#[cfg(feature = "openapi")]
+mod path_struct {
+    use either::Either;
+    use gotcha::{ParameterProvider, Path, Schematic};
+    use oas::{Parameter, ParameterIn, Referenceable};
+
+    // Only the derived Schematic impl is exercised; the fields are never read directly.
+    #[allow(dead_code)]
+    #[derive(Schematic)]
+    struct ConnectionPath {
+        user_id: String,
+        connection_id: String,
+    }
+
+    fn assert_per_field_params(params: &[Parameter]) {
+        assert_eq!(params.len(), 2, "each struct field should become one parameter");
+        for (param, name) in params.iter().zip(["user_id", "connection_id"]) {
+            assert_eq!(param.name, name);
+            assert!(matches!(param._in, ParameterIn::Path));
+            assert_eq!(param.required, Some(true));
+            let Some(Referenceable::Data(schema)) = &param.schema else {
+                panic!("parameter '{name}' should carry an inline schema");
+            };
+            assert_eq!(schema._type.as_deref(), Some("string"), "parameter '{name}' should have the field's type");
+            assert!(!schema.extras.contains_key("$ref"), "parameter '{name}' must not be a $ref to the whole struct");
+        }
+    }
+
+    #[test]
+    fn struct_fields_become_parameters() {
+        let url = "/users/{user_id}/connections/{connection_id}".to_string();
+        let result = <Path<ConnectionPath> as ParameterProvider>::generate(url);
+        match result {
+            Either::Left(params) => assert_per_field_params(&params),
+            Either::Right(_) => panic!("Path<ConnectionPath> should generate parameters, not a request body"),
+        }
+    }
+
+    #[test]
+    fn struct_fields_become_parameters_inside_a_collection_scope() {
+        // Spec assembly generates every operation inside a collection scope, where a derived
+        // struct's generate_schema() returns a bare `$ref`. Parameters must still come out
+        // per-field — not one parameter holding the whole object's `$ref`, dropping the rest.
+        let url = "/users/{user_id}/connections/{connection_id}".to_string();
+        let (result, _schemas) = gotcha_core::registry::collect(|| <Path<ConnectionPath> as ParameterProvider>::generate(url));
+        match result {
+            Either::Left(params) => assert_per_field_params(&params),
+            Either::Right(_) => panic!("Path<ConnectionPath> should generate parameters, not a request body"),
+        }
+    }
+}
+
 #[cfg(feature = "openapi")]
 #[test]
 fn test_multiple_path_params() {

gotcha_core/src/parameter.rs

@@ -84,12 +84,29 @@ impl<T1: Schematic, T2: Schematic> ParameterProvider for Path<(T1, T2)> {
 
 impl<T: Schematic> ParameterProvider for Path<T> {
     fn generate(url: String) -> Either<Vec<Parameter>, RequestBody> {
+        // Case 1: a struct extractor — each field becomes one path parameter. Read the fields
+        // directly (as `Query` does) instead of scraping `properties` out of the generated
+        // schema: during spec assembly a collection scope is active, so a derived struct's
+        // `generate_schema()` returns a bare `$ref` carrying no properties at all.
+        let fields = T::fields();
+        if !fields.is_empty() {
+            return Either::Left(
+                fields
+                    .into_iter()
+                    .map(|(name, schema)| {
+                        let desc = schema.schema.description.clone();
+                        build_param(name.to_string(), ParameterIn::Path, schema.required, schema.schema, desc)
+                    })
+                    .collect(),
+            );
+        }
+
         let mut ret = vec![];
         let mut schema = T::generate_schema();
 
-        // Check if this is a struct with properties or a simple type
+        // Check if this is a hand-written impl exposing properties or a simple type
         if let Some(mut properties) = schema.schema.extras.remove("properties") {
-            // Case 1: Struct with properties - each property becomes a path parameter
+            // Case 2: object schema with properties - each property becomes a path parameter
             if let Some(properties) = properties.as_object_mut() {
                 properties.iter_mut().for_each(|(key, value)| {
                     let schema = serde_json::from_value(value.clone()).unwrap();
@@ -98,7 +115,7 @@ impl<T: Schematic> ParameterProvider for Path<T> {
                 })
             }
         } else {
-            // Case 2: Simple type like Uuid - extract parameter name from URL
+            // Case 3: Simple type like Uuid - extract parameter name from URL
             // Since axum 0.8 a captured segment is written `{name}`, matching OpenAPI's own syntax.
             let pattern = regex::Regex::new(r"\{([^}]+)\}").unwrap();
             let param_names_in_path: Vec<String> = pattern.captures_iter(&url).map(|digits| digits.get(1).unwrap().as_str().to_string()).collect();