wip: fill out the snippets

.vscode/spellright.dict

@@ -64,3 +64,4 @@ Tokio
 asynchronicity
 constified
 SegVec
+contentful

README.md

@@ -165,15 +165,16 @@ Dioxus is heavily inspired by React, but we want your transition to feel like an
 | Custom elements           | ✅      | ✅     | Define new element primitives                               |
 | Suspense                  | ✅      | ✅     | schedule future render from future/promise                  |
 | Integrated error handling | ✅      | ✅     | Gracefully handle errors with ? syntax                      |
-| Effects                   | 🛠      | ✅     | Run effects after a component has been committed to render  |
+| Re-hydration              | 🛠      | ✅     | Pre-render to HTML to speed up first contentful paint       |
 | Cooperative Scheduling    | 🛠      | ✅     | Prioritize important events over non-important events       |
-| NodeRef                   | 🛠      | ✅     | gain direct access to nodes [1]                             |
 | Runs natively             | ✅      | ❓     | runs as a portable binary w/o a runtime (Node)              |
 | 1st class global state    | ✅      | ❓     | redux/recoil/mobx on top of context                         |
 | Subtree Memoization       | ✅      | ❓     | skip diffing static element subtrees                        |
 | Compile-time correct      | ✅      | ❓     | Throw errors on invalid template layouts                    |
 | Heuristic Engine          | 🛠      | ❓     | track component memory usage to minimize future allocations |
 | Fine-grained reactivity   | 🛠      | ❓     | Skip diffing for fine-grain updates                         |
+| Effects                   | 🛠      | ✅     | Run effects after a component has been committed to render  |
+| NodeRef                   | 🛠      | ✅     | gain direct access to nodes [1]                             |
 
 - [1] Currently blocked until we figure out a cross-platform way of exposing an imperative Node API.
 
@@ -195,7 +196,7 @@ Dioxus is heavily inspired by React, but we want your transition to feel like an
 | Feature              | Dioxus | React | Notes for Dioxus                     |
 | -------------------- | ------ | ----- | ------------------------------------ |
 | Portal               | ❓      | ✅     | cast elements through tree           |
-| Error/Panic boundary | ❓      | ✅     | catch panics and display custom BSOD |
+| Error/Panic boundary | 👀      | ✅     | catch panics and display custom BSOD |
 | Code-splitting       | 👀      | ✅     | Make bundle smaller/lazy             |
 | LiveView             | 👀      | ❓     | Example for SSR + WASM apps          |
 

examples/reference/errorhandling.rs

@@ -0,0 +1,85 @@
+//! Example: Errror Handling
+//! ------------------------
+//!
+//! Error handling in Dioxus comes in a few flavors. Because Dioxus is a Rust project, Options and Results are obviously
+//! the go-to way of wrapping possibly-errored data. However, if a component fails to "unwrapping," everything will crash,
+//! the page will deadlock, and your users will be sad.
+//!
+//! So, obviously, you need to handle your errors.
+//!
+//! Fortunately, it's easy to avoid panics, even during quick prototyping.
+//!
+//! Here's a few strategies:
+//! - Leverage the ability to return "None" and propogate None directly
+//! - Instead of propogating "None" manually, use the "?" syntax sugar
+//! - Covert Results into Options with .ok()
+//! - Manually display a separate screen by matching on Options/Results
+//!
+//! There *are* plans to add helpful screens for when apps completely panic in WASM. However, you should really try to
+//! avoid panicking.
+use dioxus::prelude::*;
+fn main() {}
+
+/// This is one way to go about error handling (just toss things away with unwrap).
+/// However, if you get it wrong, the whole app will crash.
+/// This is pretty flimsy.
+static App: FC<()> = |cx| {
+    let data = get_data().unwrap();
+    cx.render(rsx!( div { "{data}" } ))
+};
+
+/// This is a pretty verbose way of error handling
+/// However, it's still pretty good since we don't panic, just fail to render anything
+static App1: FC<()> = |cx| {
+    let data = match get_data() {
+        Some(data) => data,
+        None => return None,
+    };
+    cx.render(rsx!( div { "{data}" } ))
+};
+
+/// This is an even better form of error handling.
+/// However, it _does_ make the component go blank, which might not be desirable.
+///
+/// This type of error handling is good when you have "selectors" that produce Some/None based on some state that's
+/// already controlled for higher in the tree. IE displaying a "Username" in a component that should only be shown if
+/// a user is logged in.
+///
+/// Dioxus will throw an error in the console if the None-path is ever taken.
+static App2: FC<()> = |cx| {
+    let data = get_data()?;
+    cx.render(rsx!( div { "{data}" } ))
+};
+
+/// This is top-tier error handling since it displays a failure state.
+///
+/// However, the error is lacking in context.
+static App3: FC<()> = |cx| match get_data() {
+    Some(data) => cx.render(rsx!( div { "{data}" } )),
+    None => cx.render(rsx!( div { "Failed to load data :(" } )),
+};
+
+/// For errors that return results, it's possible short-circuit the match-based error handling with `.ok()` which converts
+/// a Result<T, V> into an Option<T> and lets you
+static App4: FC<()> = |cx| {
+    let data = get_data_err().ok()?;
+    cx.render(rsx!( div { "{data}" } ))
+};
+
+/// This is great error handling since it displays a failure state... with context!
+///
+/// Hopefully you never need to disply a screen like this. It's rather bad taste
+static App5: FC<()> = |cx| match get_data_err() {
+    Ok(data) => cx.render(rsx!( div { "{data}" } )),
+    Err(c) => cx.render(rsx!( div { "Failed to load data: {c}" } )),
+};
+
+// this fetching function produces "nothing"
+fn get_data() -> Option<String> {
+    None
+}
+
+// this fetching function produces "nothing"
+fn get_data_err() -> Result<String, &'static str> {
+    Result::Err("Failed!")
+}

packages/core-macro/Cargo.toml

@@ -12,7 +12,7 @@ description = "Core macro for Dioxus Virtual DOM"
 proc-macro = true
 
 [dependencies]
-once_cell = "1.7.2"
+once_cell = "1.8"
 proc-macro2 = { version = "1.0.6" }
 quote = "1.0"
 syn = { version = "1.0.11", features = ["full", "extra-traits"] }

packages/core/src/arena.rs

@@ -1,13 +1,13 @@
 use std::{cell::UnsafeCell, rc::Rc};
 
 use crate::innerlude::*;
-use slotmap::{DefaultKey, SlotMap};
+use slotmap::SlotMap;
 
 #[derive(Clone)]
 pub struct SharedArena {
     pub components: Rc<UnsafeCell<ScopeMap>>,
 }
-pub type ScopeMap = SlotMap<DefaultKey, Scope>;
+pub type ScopeMap = SlotMap<ScopeId, Scope>;
 
 enum MutStatus {
     Immut,

packages/core/src/bumpframe.rs

@@ -77,13 +77,14 @@ impl ActiveFrame {
         }
     }
 
-    pub fn next(&mut self) -> &mut BumpFrame {
-        *self.generation.borrow_mut() += 1;
-
-        if *self.generation.borrow() % 2 == 0 {
-            &mut self.frames[0]
-        } else {
-            &mut self.frames[1]
+    pub fn old_frame_mut(&mut self) -> &mut BumpFrame {
+        match *self.generation.borrow() & 1 == 0 {
+            true => &mut self.frames[1],
+            false => &mut self.frames[0],
         }
     }
+
+    pub fn cycle_frame(&mut self) {
+        *self.generation.borrow_mut() += 1;
+    }
 }

packages/core/src/context.rs

@@ -115,6 +115,11 @@ impl<'src, P> Context<'src, P> {
         todo!()
     }
 
+    /// Get's this context's ScopeId
+    pub fn get_scope_id(&self) -> ScopeId {
+        self.scope.our_arena_idx.clone()
+    }
+
     /// Take a lazy VNode structure and actually build it with the context of the VDom's efficient VNode allocator.
     ///
     /// This function consumes the context and absorb the lifetime, so these VNodes *must* be returned.
@@ -200,7 +205,11 @@ Any function prefixed with "use" should not be called conditionally.
     ///
     ///
     ///
-    pub fn use_create_context<T: 'static>(&self, init: impl Fn() -> T) {
+    pub fn use_context_provider<T, F>(self, init: F) -> &'src Rc<T>
+    where
+        T: 'static,
+        F: FnOnce() -> T,
+    {
         let mut cxs = self.scope.shared_contexts.borrow_mut();
         let ty = TypeId::of::<T>();
 
@@ -225,7 +234,8 @@ Any function prefixed with "use" should not be called conditionally.
             }
 
             _ => debug_assert!(false, "Cannot initialize two contexts of the same type"),
-        }
+        };
+        self.use_context::<T>()
     }
 
     /// There are hooks going on here!
@@ -234,26 +244,19 @@ Any function prefixed with "use" should not be called conditionally.
     }
 
     /// Uses a context, storing the cached value around
-    pub fn try_use_context<T: 'static>(self) -> Result<&'src Rc<T>> {
+    ///
+    /// If a context is not found on the first search, then this call will be  "dud", always returning "None" even if a
+    /// context was added later. This allows using another hook as a fallback
+    ///
+    pub fn try_use_context<T: 'static>(self) -> Option<&'src Rc<T>> {
         struct UseContextHook<C> {
             par: Option<Rc<C>>,
-            we: Option<Weak<C>>,
         }
 
         self.use_hook(
-            move |_| UseContextHook {
-                par: None as Option<Rc<T>>,
-                we: None as Option<Weak<T>>,
-            },
-            move |hook| {
+            move |_| {
                 let mut scope = Some(self.scope);
-
-                if let Some(we) = &hook.we {
-                    if let Some(re) = we.upgrade() {
-                        hook.par = Some(re);
-                        return Ok(hook.par.as_ref().unwrap());
-                    }
-                }
+                let mut par = None;
 
                 let ty = TypeId::of::<T>();
                 while let Some(inner) = scope {
@@ -270,26 +273,21 @@ Any function prefixed with "use" should not be called conditionally.
                             .downcast::<T>()
                             .expect("Should not fail, already validated the type from the hashmap");
 
-                        hook.we = Some(Rc::downgrade(&rc));
-                        hook.par = Some(rc);
-                        return Ok(hook.par.as_ref().unwrap());
+                        par = Some(rc);
+                        break;
                     } else {
                         match inner.parent_idx {
                             Some(parent_id) => {
-                                let parent = inner
-                                    .arena_link
-                                    .get(parent_id)
-                                    .ok_or_else(|| Error::FatalInternal("Failed to find parent"))?;
-
-                                scope = Some(parent);
+                                scope = inner.arena_link.get(parent_id);
                             }
-                            None => return Err(Error::MissingSharedContext),
+                            None => break,
                         }
                     }
                 }
-
-                Err(Error::MissingSharedContext)
+                //
+                UseContextHook { par }
             },
+            move |hook| hook.par.as_ref(),
             |_| {},
         )
     }

packages/core/src/error.rs

@@ -19,6 +19,9 @@ pub enum Error {
     #[error("Wrong Properties Type")]
     WrongProps,
 
+    #[error("The component failed to return VNodes")]
+    ComponentFailed,
+
     #[error("Base scope has not been mounted yet")]
     NotMounted,
 

packages/core/src/lib.rs

@@ -10,7 +10,7 @@
 //!
 
 pub use crate::innerlude::{
-    format_args_f, html, rsx, Context, DioxusElement, DomEdit, EventTrigger, LazyNodes,
+    format_args_f, html, rsx, Context, DioxusElement, DomEdit, DomTree, EventTrigger, LazyNodes,
     NodeFactory, Properties, RealDom, RealDomNode, ScopeId, VNode, VNodeKind, VirtualDom,
     VirtualEvent, FC,
 };

packages/core/src/nodes.rs

@@ -267,6 +267,22 @@ impl<'a> NodeFactory<'a> {
         }
     }
 
+    pub fn attr_with_alloc_val(
+        &self,
+        name: &'static str,
+        val: &'a str,
+        namespace: Option<&'static str>,
+        is_volatile: bool,
+    ) -> Attribute<'a> {
+        Attribute {
+            name,
+            value: val,
+            is_static: false,
+            namespace,
+            is_volatile,
+        }
+    }
+
     pub fn component<P>(
         &self,
         component: FC<P>,
@@ -508,6 +524,14 @@ impl IntoVNode<'_> for Option<()> {
         cx.fragment_from_iter(None as Option<VNode>)
     }
 }
+impl<'a> IntoVNode<'a> for Option<VNode<'a>> {
+    fn into_vnode(self, cx: NodeFactory<'a>) -> VNode<'a> {
+        match self {
+            Some(n) => n,
+            None => cx.fragment_from_iter(None as Option<VNode>),
+        }
+    }
+}
 
 impl Debug for NodeFactory<'_> {
     fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {

packages/core/src/scope.rs

@@ -113,7 +113,8 @@ impl Scope {
         // Remove all the outdated listeners
 
         // This is a very dangerous operation
-        self.frames.next().bump.reset();
+        let next_frame = self.frames.old_frame_mut();
+        next_frame.bump.reset();
 
         self.listeners.borrow_mut().clear();
 
@@ -123,16 +124,19 @@ impl Scope {
         // Cast the caller ptr from static to one with our own reference
         let c3: &WrappedCaller = self.caller.as_ref();
 
-        self.frames.cur_frame_mut().head_node = unsafe { self.call_user_component(c3) };
-
-        Ok(())
-    }
-
-    // this is its own function so we can preciesly control how lifetimes flow
-    unsafe fn call_user_component<'a>(&'a self, caller: &WrappedCaller) -> VNode<'static> {
-        let new_head: Option<VNode<'a>> = caller(self);
-        let new_head = new_head.unwrap_or(errored_fragment());
-        std::mem::transmute(new_head)
+        match c3(self) {
+            None => {
+                // the user's component failed. We avoid cycling to the next frame
+                log::error!("Running your component failed! It will no longer receive events.");
+                Err(Error::ComponentFailed)
+            }
+            Some(new_head) => {
+                // the user's component succeeded. We can safely cycle to the next frame
+                self.frames.old_frame_mut().head_node = unsafe { std::mem::transmute(new_head) };
+                self.frames.cycle_frame();
+                Ok(())
+            }
+        }
     }
 
     // A safe wrapper around calling listeners

packages/core/src/virtual_dom.rs

@@ -30,7 +30,9 @@ use std::any::TypeId;
 use std::cell::RefCell;
 use std::pin::Pin;
 
-pub type ScopeId = DefaultKey;
+slotmap::new_key_type! {
+    pub struct ScopeId;
+}
 
 /// An integrated virtual node system that progresses events and diffs UI trees.
 /// Differences are converted into patches which a renderer can use to draw the UI.
@@ -140,7 +142,7 @@ impl VirtualDom {
     /// let dom = VirtualDom::new(Example);
     /// ```
     pub fn new_with_props<P: Properties + 'static>(root: FC<P>, root_props: P) -> Self {
-        let components = SharedArena::new(SlotMap::new());
+        let components = SharedArena::new(SlotMap::<ScopeId, Scope>::with_key());
 
         let root_props: Pin<Box<dyn Any>> = Box::pin(root_props);
         let props_ptr = root_props.as_ref().downcast_ref::<P>().unwrap() as *const P;
@@ -225,11 +227,12 @@ impl VirtualDom {
         );
 
         let cur_component = self.components.get_mut(self.base_scope).unwrap();
-        cur_component.run_scope()?;
 
-        let meta = diff_machine.create(cur_component.next_frame());
-
-        diff_machine.edits.append_children(meta.added_to_stack);
+        // We run the component. If it succeeds, then we can diff it and add the changes to the dom.
+        if cur_component.run_scope().is_ok() {
+            let meta = diff_machine.create(cur_component.next_frame());
+            diff_machine.edits.append_children(meta.added_to_stack);
+        }
 
         Ok(())
     }
@@ -370,10 +373,10 @@ impl VirtualDom {
                     // We are guaranteeed that this scope is unique because we are tracking which nodes have modified
                     let cur_component = self.components.get_mut(update.idx).unwrap();
 
-                    cur_component.run_scope()?;
-
-                    let (old, new) = (cur_component.old_frame(), cur_component.next_frame());
-                    diff_machine.diff_node(old, new);
+                    if cur_component.run_scope().is_ok() {
+                        let (old, new) = (cur_component.old_frame(), cur_component.next_frame());
+                        diff_machine.diff_node(old, new);
+                    }
                 }
             }
         }

packages/hooks/src/usestate.rs

@@ -106,7 +106,7 @@ impl<'a, T: 'static> UseState<'a, T> {
         *self.inner.wip.borrow_mut() = Some(new_val);
     }
 
-    pub fn get(&self) -> &T {
+    pub fn get(&self) -> &'a T {
         &self.inner.current_val
     }
 

packages/web/Cargo.toml

@@ -21,8 +21,7 @@ pretty_env_logger = "0.4.0"
 console_error_panic_hook = "0.1.6"
 generational-arena = "0.2.8"
 wasm-bindgen-test = "0.3.21"
-once_cell = "1.7.2"
-# atoms = { path = "../atoms" }
+once_cell = "1.8"
 async-channel = "1.6.1"
 anyhow = "1.0.41"
 slotmap = "1.0.3"