more fullstack cleanups: loaders serialize, ServeConfig only (#4785)

* some opinionated cleanups in dioxus-server

* add serialize to loader

* add `result` to Resource

* clippy

* fix

* writable memos, resources, `onmount`, `.pending`, and `.value()` on actions

* fix compile issues

* fix typo

packages/fullstack-server/src/index_html.rs

@@ -0,0 +1,83 @@
+use anyhow::Context;
+
+/// An `IndexHtml` represents the contents of an `index.html` file used to serve a web application.
+///
+/// This defines the static portion of your web application, typically generated by a tool like `dx`
+/// in conjunction with wasm-bindgen.
+#[derive(Clone, Debug)]
+pub(crate) struct IndexHtml {
+    pub(crate) head_before_title: String,
+    pub(crate) head_after_title: String,
+    pub(crate) title: String,
+    pub(crate) close_head: String,
+    pub(crate) post_main: String,
+    pub(crate) after_closing_body_tag: String,
+}
+
+impl IndexHtml {
+    /// Create a new `IndexHtml` from the raw contents of an `index.html` file.
+    ///
+    /// This function will parse the `index.html` and split it into sections for easier manipulation.
+    /// The `root_id` parameter specifies the id of the main application container (e.g., "main")
+    /// which your app will render into.
+    pub(crate) fn new(contents: &str, root_id: &'static str) -> Result<IndexHtml, anyhow::Error> {
+        let (pre_main, post_main) = contents.split_once(&format!("id=\"{root_id}\""))
+            .with_context(|| format!("Failed to find id=\"{root_id}\" in index.html. The id is used to inject the application into the page."))?;
+
+        let post_main = post_main.split_once('>').with_context(|| {
+            format!("Failed to find closing > after id=\"{root_id}\" in index.html.")
+        })?;
+
+        let (pre_main, post_main) = (
+            pre_main.to_string() + &format!("id=\"{root_id}\"") + post_main.0 + ">",
+            post_main.1.to_string(),
+        );
+
+        let (head, close_head) = pre_main.split_once("</head>").with_context(|| {
+            format!("Failed to find closing </head> tag after id=\"{root_id}\" in index.html.")
+        })?;
+
+        let (head, close_head) = (head.to_string(), "</head>".to_string() + close_head);
+
+        let (post_main, after_closing_body_tag) =
+            post_main.split_once("</body>").with_context(|| {
+                format!("Failed to find closing </body> tag after id=\"{root_id}\" in index.html.")
+            })?;
+
+        // Strip out the head if it exists
+        let mut head_before_title = String::new();
+        let mut head_after_title = head;
+        let mut title = String::new();
+        if let Some((new_head_before_title, new_title)) = head_after_title.split_once("<title>") {
+            let (new_title, new_head_after_title) = new_title
+                .split_once("</title>")
+                .context("Failed to find closing </title> tag after <title> in index.html.")?;
+            title = format!("<title>{new_title}</title>");
+            head_before_title = new_head_before_title.to_string();
+            head_after_title = new_head_after_title.to_string();
+        }
+
+        Ok(IndexHtml {
+            head_before_title,
+            head_after_title,
+            title,
+            close_head,
+            post_main: post_main.to_string(),
+            after_closing_body_tag: "</body>".to_string() + after_closing_body_tag,
+        })
+    }
+}
+
+impl Default for IndexHtml {
+    fn default() -> Self {
+        const DEFAULT: &str = r#"<!DOCTYPE html>
+        <html>
+            <head> </head>
+            <body>
+                <div id="main"></div>
+            </body>
+        </html>"#;
+
+        Self::new(DEFAULT, "main").expect("Failed to load default index.html")
+    }
+}