history: Use OnceCell instead of RefCell<Option<_>> for thread locals

Author: jplatte

crates/history/src/browser.rs

@@ -1,6 +1,6 @@
 use std::any::Any;
 use std::borrow::Cow;
-use std::cell::RefCell;
+use std::cell::{OnceCell, RefCell};
 use std::fmt;
 use std::rc::Rc;
 
@@ -250,46 +250,40 @@ impl Default for BrowserHistory {
     fn default() -> Self {
         // We create browser history only once.
         thread_local! {
-            static BROWSER_HISTORY: RefCell<Option<BrowserHistory>> = RefCell::default();
-            static LISTENER: RefCell<Option<EventListener>> = RefCell::default();
+            static BROWSER_HISTORY: OnceCell<BrowserHistory> = OnceCell::default();
+            static LISTENER: OnceCell<EventListener> = OnceCell::default();
         }
 
-        BROWSER_HISTORY.with(|m| {
-            let mut m = m.borrow_mut();
-
-            match *m {
-                Some(ref m) => m.clone(),
-                None => {
-                    let window = window();
-
-                    let inner = window
-                        .history()
-                        .expect_throw("Failed to create browser history. Are you using a browser?");
-                    let callbacks = Rc::default();
-
-                    let history = Self {
-                        inner,
-                        callbacks,
-                        states: Rc::default(),
-                    };
-
-                    {
-                        let history = history.clone();
-
-                        // Listens to popstate.
-                        LISTENER.with(move |m| {
-                            let mut listener = m.borrow_mut();
-
-                            *listener = Some(EventListener::new(&window, "popstate", move |_| {
-                                history.notify_callbacks();
-                            }));
-                        });
-                    }
-
-                    *m = Some(history.clone());
-                    history
+        BROWSER_HISTORY.with(|b| {
+            b.get_or_init(|| {
+                let window = window();
+
+                let inner = window
+                    .history()
+                    .expect_throw("Failed to create browser history. Are you using a browser?");
+                let callbacks = Rc::default();
+
+                let history = Self {
+                    inner,
+                    callbacks,
+                    states: Rc::default(),
+                };
+
+                {
+                    let history = history.clone();
+
+                    // Listens to popstate.
+                    LISTENER.with(move |l| {
+                        l.set(EventListener::new(&window, "popstate", move |_| {
+                            history.notify_callbacks();
+                        }))
+                        .expect("this function is only called once");
+                    });
                 }
-            }
+
+                history
+            })
+            .clone()
         })
     }
 }

crates/history/src/hash.rs

@@ -1,5 +1,5 @@
 use std::borrow::Cow;
-use std::cell::RefCell;
+use std::cell::OnceCell;
 use std::fmt;
 
 use gloo_utils::window;
@@ -238,36 +238,29 @@ impl HashHistory {
 impl Default for HashHistory {
     fn default() -> Self {
         thread_local! {
-            static HASH_HISTORY: RefCell<Option<HashHistory>> = RefCell::default();
+            static HASH_HISTORY: OnceCell<HashHistory> = OnceCell::default();
         }
 
-        HASH_HISTORY.with(|m| {
-            let mut m = m.borrow_mut();
+        HASH_HISTORY.with(|h| {
+            h.get_or_init(|| {
+                let browser_history = BrowserHistory::new();
+                let browser_location = browser_history.location();
 
-            match *m {
-                Some(ref m) => m.clone(),
-                None => {
-                    let browser_history = BrowserHistory::new();
-                    let browser_location = browser_history.location();
+                let current_hash = browser_location.hash();
 
-                    let current_hash = browser_location.hash();
+                // Hash needs to start with #/.
+                if current_hash.is_empty() || !current_hash.starts_with("#/") {
+                    let url = Self::get_url();
+                    url.set_hash("#/");
 
-                    // Hash needs to start with #/.
-                    if current_hash.is_empty() || !current_hash.starts_with("#/") {
-                        let url = Self::get_url();
-                        url.set_hash("#/");
-
-                        browser_history.replace(url.href());
-                    }
-
-                    let history = Self {
-                        inner: browser_history,
-                    };
+                    browser_history.replace(url.href());
+                }
 
-                    *m = Some(history.clone());
-                    history
+                Self {
+                    inner: browser_history,
                 }
-            }
+            })
+            .clone()
         })
     }
 }