Blog: v0.23 release

src/Website/articles/20231106-bolero-0-23-released.md

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+---
+title: Bolero 0.23 released
+subtitle: Router query parameters and .NET 8 compatibility
+---
+
+We are happy to announce the release of [Bolero](https://fsbolero.io) version 0.23.
+Bolero is a library that enables writing full-stack applications in F#, whose client side runs in WebAssembly using Blazor.
+
+The main highlights of this release are:
+* Improvements to routing, including query parameters, not-found handling and hash scrolling.
+* .NET 8 compatibility.
+* Better C# compatibility for server-side.
+
+Install the latest project template with:
+
+```
+dotnet new -i Bolero.Templates::0.23.10
+```
+
+## Routing improvements
+
+### Query parameters ([#309](https://github.com/fsbolero/Bolero/issues/309))
+
+Inferred routers can now handle query parameter parsing. It is done using the syntax `?paramName={fieldName}`.
+
+```fsharp
+type Page =
+    | [<EndPoint "/">] Home
+    | [<EndPoint "/articles?page={pageNum}&count={countPerPage}"] Articles of pageNum: int * countPerPage: int
+```
+
+Using the router above, `/articles?page=3&count=20` corresponds to the page value `Articles (3, 20)`.
+
+Query parameters are optional if the corresponding field has type `option` or `voption`, and mandatory otherwise.
+
+Additionally, the syntax `?{paramName}` is short for `?paramName={paramName}`.
+
+```fsharp
+type Page =
+    | [<EndPoint "/articles?{tag}&{page}&{count}"] Articles of tag: string option * page: int option * count: int
+```
+
+Using the router above, `/articles?tag=fsharp&count=20` corresponds to the page value `Articles (Some "fsharp", None, 20)`.
+
+Of course, path parameters and query parameters can be mixed in the same endpoint.
+
+```fsharp
+type Page =
+    | [<EndPoint "/articles/{tag}?{page}"] Articles of tag: string * page: int option
+```
+
+Using the router above, `/articles/fsharp?page=20` corresponds to the page value `Articles ("fsharp", Some 20)`.
+
+### "Not found" handler ([#308](https://github.com/fsbolero/Bolero/issues/308))
+
+Routers can indicate what endpoint to use when the URL is invalid using the function `Router.withNotFound`.
+
+```
+type Page =
+    | Home
+    | // ...
+
+type Message =
+    | SetPage of Page
+    | // ...
+
+type Model =
+    { page: Page
+      // ...
+    }
+
+let router =
+    Router.infer PageChanged (fun m -> m.page)
+    |> Router.withNotFound Home
+```
+
+This function applies when the initial URL is invalid, or when the URL is programmatically changed to be invalid.
+It does not apply when the user clicks a link to an invalid URL, in order to allow external links.
+
+### Inner links with hashes ([#315](https://github.com/fsbolero/Bolero/issues/315))
+
+Navigating to a Bolero routed URL with a `#hash` will properly scroll to the element named `hash` in the target page.
+
+```fsharp
+div {
+    h1 {
+        attr.id "the-title"
+        "The title of this section"
+    }
+    a {
+        attr.href (router.Link Home + "#the-title")
+        "Navigate and scroll to the title of this section"
+    }
+}
+```
+
+Additionally, the methods `IRouter.Link` and `IRouter.HRef` take a new optional argument `hash: string` to link to the corresponding `#hash` in the target page.
+
+```fsharp
+div {
+    h1 {
+        attr.id "the-title"
+        "The title of this section"
+    }
+    a {
+        router.HRef(Home, hash = "the-title")
+        "Navigate and scroll to the title of this section"
+    }
+}
+```
+
+## .NET 8 Compatibility fixes ([#317](https://github.com/fsbolero/Bolero/issues/317))
+
+* Fix the server-side rendering and prerendering for .NET 8.
+
+* Update the MSBuild task generating scoped CSS.
+
+## C# compatibility of server-side APIs ([#313](https://github.com/fsbolero/Bolero/issues/313))
+
+C# compatibility has been improved for server-side hosting APIs, in order to make it easier to integrate Bolero into an existing C# ASP.NET Core application.
+
+More specifically, for the following extension methods:
+
+* `IServiceCollection.AddBoleroHost`
+* `IServiceCollection.AddBoleroRouting`
+* `IEndpointRouteBuilder.MapFallbackToBolero`
+
+The following changes are applied:
+
+* Optional arguments are changed from F#-style to C#-style. This is a source breaking change for callers who use explicit syntax `?argument = optionValue`.
+* Function arguments are changed from F#-style functions to C#-style `Func` or `Action`.
+
+These changes should be source-compatible for most existing F# host applications.
+
+## Event handler fixes
+
+* Fix `on.stopPropagation` and `on.preventDefault` to take event names without the `on` prefix, for consistency with `on.event`. ([#316](https://github.com/fsbolero/Bolero/issues/316))
+
+* Use `WheelEventArgs` for wheel events and `ErrorEventArgs` for `on.error`. ([#323](https://github.com/fsbolero/Bolero/issues/323))
+
+Happy coding!