fix: hydration of empty VLists

an additional (empty) VText was inserted in the second reconciliation
pass, which tried to insert itself in an invalid position. This internal
error was masked by a "fix" of the internal slot of components, which
should have still been trapped to signal that the second fixup render
was not yet run.

packages/yew/src/dom_bundle/blist.rs

@@ -11,7 +11,7 @@ use super::{test_log, BNode, BSubtree, DomSlot};
 use crate::dom_bundle::{Reconcilable, ReconcileTarget};
 use crate::html::AnyScope;
 use crate::utils::RcExt;
-use crate::virtual_dom::{Key, VList, VNode, VText};
+use crate::virtual_dom::{Key, VList, VNode};
 
 /// This struct represents a mounted [VList]
 #[derive(Debug)]
@@ -427,15 +427,7 @@ impl Reconcilable for VList {
         // The left items are known since we want to insert them
         // (self.children). For the right ones, we will look at the bundle,
         // i.e. the current DOM list element that we want to replace with self.
-        let (key, mut fully_keyed, mut lefts) = self.split_for_blist();
-
-        if lefts.is_empty() {
-            // Without a placeholder the next element becomes first
-            // and corrupts the order of rendering
-            // We use empty text element to stake out a place
-            lefts.push(VText::new("").into());
-            fully_keyed = false;
-        }
+        let (key, fully_keyed, lefts) = self.split_for_blist();
 
         let rights = &mut blist.rev_children;
         test_log!("lefts: {:?}", lefts);

packages/yew/src/dom_bundle/utils.rs

@@ -51,6 +51,11 @@ mod feat_hydration {
 #[cfg(feature = "hydration")]
 pub(super) use feat_hydration::*;
 
+#[cfg(test)]
+// this is needed because clippy doesn't like the import not being used
+#[allow(unused_imports)]
+pub(super) use tests::*;
+
 #[cfg(test)]
 mod tests {
     #![allow(dead_code)]
@@ -87,8 +92,3 @@ mod tests {
         (root, scope, parent, sibling)
     }
 }
-
-#[cfg(test)]
-// this is needed because clippy doesn't like the import not being used
-#[allow(unused_imports)]
-pub(super) use tests::*;

packages/yew/src/html/component/lifecycle.rs

@@ -430,7 +430,9 @@ impl ComponentState {
         fields(component.id = self.comp_id)
     )]
     fn render(&mut self, shared_state: &Shared<Option<ComponentState>>) {
-        match self.inner.view() {
+        let view = self.inner.view();
+        tracing::trace!(?view, "render result");
+        match view {
             Ok(vnode) => self.commit_render(shared_state, vnode),
             Err(RenderError::Suspended(susp)) => self.suspend(shared_state, susp),
         };

packages/yew/src/html/component/scope.rs

@@ -642,7 +642,7 @@ mod feat_hydration {
     use web_sys::{Element, HtmlScriptElement};
 
     use super::*;
-    use crate::dom_bundle::{BSubtree, DomSlot, DynamicDomSlot, Fragment};
+    use crate::dom_bundle::{BSubtree, DynamicDomSlot, Fragment};
     use crate::html::component::lifecycle::{ComponentRenderState, CreateRunner, RenderRunner};
     use crate::scheduler;
     use crate::virtual_dom::Collectable;
@@ -679,12 +679,6 @@ mod feat_hydration {
             let collectable = Collectable::for_component::<COMP>();
 
             let mut fragment = Fragment::collect_between(fragment, &collectable, &parent);
-            let next_sibling = if let Some(n) = fragment.front() {
-                Some(n.clone())
-            } else {
-                fragment.sibling_at_end().cloned()
-            };
-            internal_ref.reassign(DomSlot::create(next_sibling));
 
             let prepared_state = match fragment
                 .back()