fix errors

Author: rmorshea

docs/source/_custom_js/package-lock.json

@@ -417,10 +417,18 @@ def _render_model_children(
     def _render_model_children_without_old_state(
         self, new_state: _ModelState, raw_children: List[Any]
     ) -> None:
+        child_type_key_tuples = list(_process_child_type_and_key(raw_children))
+
+        new_keys = {item[2] for item in child_type_key_tuples}
+        if len(new_keys) != len(raw_children):
+            key_counter = Counter(item[2] for item in child_type_key_tuples)
+            duplicate_keys = [key for key, count in key_counter.items() if count > 1]
+            raise ValueError(
+                f"Duplicate keys {duplicate_keys} at {new_state.patch_path or '/'!r}"
+            )
+
         new_children = new_state.model.current["children"] = []
-        for index, (child, child_type, key) in enumerate(
-            _process_child_type_and_key(raw_children)
-        ):
+        for index, (child, child_type, key) in enumerate(child_type_key_tuples):
             if child_type is _DICT_TYPE:
                 child_state = _make_element_model_state(new_state, index, key)
                 self._render_model(None, child_state, child)

src/idom/core/layout.py

@@ -1,4 +1,8 @@
 """
+**Fragment**
+
+- :func:`_`
+
 **Dcument metadata**
 
 - :func:`base`
@@ -148,6 +152,8 @@
 
 - :func:`slot`
 - :func:`template`
+
+.. autofunction:: _
 """
 
 from __future__ import annotations
@@ -158,6 +164,14 @@
 from .core.vdom import coalesce_attributes_and_children, make_vdom_constructor
 
 
+def _(*children: Any) -> VdomDict:
+    """An HTML fragment - this element will not appear in the DOM"""
+    attributes, children = coalesce_attributes_and_children(children)
+    if attributes:
+        raise ValueError("Fragments cannot have attributes")
+    return {"tagName": "", "children": children}
+
+
 # Dcument metadata
 base = make_vdom_constructor("base")
 head = make_vdom_constructor("head")

src/idom/html.py

@@ -148,7 +148,7 @@ def Child():
         child_set_state.current(1)
         path, changes = await render_json_patch(layout)
 
-        assert path == "/children/1"
+        assert path == "/children/0/children/1"
         assert changes == [
             {"op": "replace", "path": "/children/0/children/0", "value": "1"}
         ]
@@ -225,21 +225,31 @@ def BadChild():
             assert_same_items(
                 patch.changes,
                 [
-                    {"op": "add", "path": "/tagName", "value": ""},
                     {
                         "op": "add",
                         "path": "/children",
                         "value": [
                             {
                                 "children": [
-                                    {"children": [...], "tagName": ""},
+                                    {
+                                        "children": [
+                                            {"children": ["hello"], "tagName": "div"}
+                                        ],
+                                        "tagName": "",
+                                    },
                                     {"error": "", "tagName": ""},
-                                    {"children": [...], "tagName": ""},
+                                    {
+                                        "children": [
+                                            {"children": ["hello"], "tagName": "div"}
+                                        ],
+                                        "tagName": "",
+                                    },
                                 ],
                                 "tagName": "div",
                             }
                         ],
                     },
+                    {"op": "add", "path": "/tagName", "value": ""},
                 ],
             )
 
@@ -598,9 +608,14 @@ def Inner():
                 {
                     "op": "add",
                     "path": "/children",
-                    "value": [{"children": ["hello"], "tagName": "div"}],
+                    "value": [
+                        {
+                            "children": [{"children": ["hello"], "tagName": "div"}],
+                            "tagName": "",
+                        }
+                    ],
                 },
-                {"op": "add", "path": "/tagName", "value": "div"},
+                {"op": "add", "path": "/tagName", "value": ""},
             ],
         )
 
@@ -685,18 +700,31 @@ def HasNestedEventHandler():
 
 
 async def test_duplicate_sibling_keys_causes_error(caplog):
+    hook = HookCatcher()
+
     @idom.component
+    @hook.capture
     def ComponentReturnsDuplicateKeys():
         return idom.html.div(
-            idom.html.div(key="duplicate"), idom.html.div(key="duplicate")
+            idom.html.div(key="duplicate"),
+            idom.html.div(key="duplicate"),
         )
 
-    with assert_idom_logged(
-        error_type=ValueError,
-        match_error=r"Duplicate keys \['duplicate'\] at '/'",
-        clear_matched_records=True,
-    ):
-        with idom.Layout(ComponentReturnsDuplicateKeys()) as layout:
+    with idom.Layout(ComponentReturnsDuplicateKeys()) as layout:
+        with assert_idom_logged(
+            error_type=ValueError,
+            match_error=r"Duplicate keys \['duplicate'\] at '/children/0'",
+            clear_matched_records=True,
+        ):
+            await layout.render()
+
+        hook.latest.schedule_render()
+
+        with assert_idom_logged(
+            error_type=ValueError,
+            match_error=r"Duplicate keys \['duplicate'\] at '/children/0'",
+            clear_matched_records=True,
+        ):
             await layout.render()