v0.24 announcement

src/Website/articles/20241209-bolero-0-24-released.md

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+---
+title: Bolero 0.24 released
+subtitle: Interactive render modes
+---
+
+We are happy to announce the release of [Bolero](https://fsbolero.io) version 0.24.
+Bolero is a library that enables writing full-stack appications in F#, whose interactivity runs in WebAssembly or on the server side using Blazor.
+
+The main highlights of this release are:
+* Support for Interactive render modes
+* Support for Streaming rendering.
+
+Install the latest project template with:
+
+```sh
+dotnet new -i Bolero.Templates::0.24.38
+```
+
+## Interactive render modes
+
+Bolero now supports the [Interactive render modes](https://learn.microsoft.com/en-us/aspnet/core/blazor/components/render-modes) which were introduced in Blazor 8.
+This is a new way of deciding whether dynamic content should be rendered on the server side or in WebAssembly, incompatible with the existing `IBoleroHostConfig`-based method.
+
+The Bolero project template now uses InteractiveWebAssembly mode by default. You can toggle it with the `--render` argument:
+
+```sh
+dotnet new bolero-app --render=InteractiveAuto
+dotnet new bolero-app --render=InteractiveServer
+dotnet new bolero-app --render=InteractiveWebAssembly
+dotnet new bolero-app --render=LegacyServer      # "classic" server-side mode
+dotnet new bolero-app --render=LegacyWebAssembly # "classic" WebAssembly mode
+```
+
+To switch an existing project to the new mode:
+
+* Make sure you are using Bolero HTML for your static content.
+
+* Wrap your `index` page definition in a component:
+
+    ```fsharp
+    [<Route "/{*path}">]
+    type Page() =
+        inherit Bolero.Component()
+        override _.Render() = index
+    ```
+
+* In the server-side dependency injection: replace `AddBoleroHost()` with `AddBoleroComponents()`.
+
+* In the server-side endpoints configuration, replace this:
+
+    ```fsharp
+    endpoints.MapDefaultToBolero(index) |> ignore
+    ```
+
+    with:
+
+    ```fsharp
+    endpoints.MapRazorComponents<Page>()
+        // If you use Server or Auto render mode:
+        .AddInteractiveServerRenderMode()
+        // If you use WebAssembly or Auto render mode:
+        .AddInteractiveWebAssemblyRenderMode()
+        // List here your client assemblies:
+        .AddAdditionalAssemblies(typeof<MyApp>.Assembly)
+    |> ignore
+    ```
+
+* On your root dynamic component(s), use one of the following to decide its render mode:
+
+    * `BoleroRenderMode` on the component itself:
+
+        ```fsharp
+        // Note: prerender is true if not specified.
+        [<BoleroRenderMode(BoleroRenderMode.Auto, prerender = false)>]
+        type MyApp() =
+            // ...
+        ```
+
+        OR
+
+    * `attr.renderMode` when creating an instance of the component:
+
+        ```fsharp
+        open Microsoft.AspNetCore.Components.Web
+
+        let index = doctypeHtml {
+            head { (* ... *) }
+            body {
+                // Default (ie with prerender=true):
+                comp<MyApp> { attr.renderMode RenderMode.InteractiveAuto }
+
+                // Custom (here with prerender=false):
+                comp<MyApp> { attr.renderMode (InteractiveAutoRenderMode(prerender = false)) }
+
+                boleroScript
+            }
+        }
+        ```
+
+    * If neither of these are used, then the render mode will be Static Server (ie no interactive content).
+
+## Streaming rendering
+
+Bolero now supports [streaming rendering](https://learn.microsoft.com/en-us/aspnet/core/blazor/components/rendering?view=aspnetcore-9.0#streaming-rendering) in two different ways:
+
+* Streaming rendering in the Elmish program, using `Program.mkStreamRendering` or `Program.mkSimpleStreamRendering`:
+
+    ```fsharp
+    type Model = { text: string }
+
+    [<StreamRendering true>]
+    type MyApp() =
+        inherit ProgramComponent<Model, Message>()
+
+        override this.Program =
+            let initModel = { text = "Loading..." }
+
+            let load initialModel = task {
+                let! loadedText = myRemoteApi.getText ()
+                return { initialModel with text = $"Loaded {loadedText}!" }, Cmd.none
+            }
+
+            Program.mkStreamRendering initModel load update view
+    ```
+
+* Streaming rendering on a (non-Elmish) component by inheriting from `StreamRenderingComponent<'model>`:
+
+    ```fsharp
+    type Model = { text: string }
+
+    type MyStreamedComponent() =
+        inherit StreamRenderingComponent<Model>()
+
+        override _.InitialModel = { text = "Loading..." }
+
+        override _.LoadModel(initialModel) = task {
+            let! loadedText = myRemoteApi.getText ()
+            return { initialModel with text = $"Loaded {loadedText}!" }, Cmd.none
+        }
+    ```
+
+## .NET 9 and F# 9 improvements
+
+This is not part of Bolero 0.24, but since [.NET 9 and F# 9 were recently released](https://devblogs.microsoft.com/dotnet/announcing-dotnet-9/), we would like to highlight some improvements that are relevant to Bolero:
+
+* Tooling performance has been greatly improved around large and nested computation expressions. This should make the experience of editing HTML-heavy source files much more pleasant.
+
+* It is now possible to create empty computation expressions. For example, to create an empty `div` element, instead of:
+
+    ```fsharp
+    div { attr.empty() }
+    ```
+
+    You can now simply write:
+
+    ```fsharp
+    div {}
+    ```
+
+* (On Blazor 9 only) Dependency injection can now be done using constructor arguments, rather than properties with the `Inject` attribute.
+
+    ```fsharp
+    // Blazor 8:
+    type MyOldComponent() =
+        inherit Component()
+
+        [<Inject>]
+        member val JS = Unchecked.defaultof<IJSRuntime> with get, set
+
+        override this.Render() =
+            this.JS.InvokeAsync("console.log", "Hello world!") |> ignore
+            div { attr.empty() }
+
+    // Blazor 9:
+    type MyNewComponent(js: IJSRuntime) =
+        inherit Component()
+
+        override this.Render() =
+            js.InvokeAsync("console.log", "Hello world!") |> ignore
+            div {}
+    ```
+
+## .NET 6 and .NET 7 notice
+
+Bolero 0.24 will be the last version of Bolero supporting .NET 6 and .NET 7 (which are already out of support by Microsoft). Starting with Bolero 0.25, .NET 8 will be the minimum supported version.
+
+Happy coding!