[Repo Assist] Add --root option to fsdocs watch for remote/proxy hosting

RELEASE_NOTES.md

@@ -16,6 +16,8 @@
 ## [22.0.0-alpha.2] - 2026-03-13
 
 ### Added
+* Add `--root` option to `fsdocs watch` to override the root URL for generated pages. Useful for serving docs via GitHub Codespaces, reverse proxies, or other remote hosting where `localhost` URLs are inaccessible. E.g. `fsdocs watch --root /` or `fsdocs watch --root https://example.com/docs/`. When not set, defaults to `http://localhost:<port>/` as before. [#924](https://github.com/fsprojects/FSharp.Formatting/issues/924)
+* Fix `fsdocs watch` hot-reload WebSocket to connect using the page's actual host (`window.location.host`) instead of a hardcoded `localhost:<port>`, so hot-reload works correctly in GitHub Codespaces, behind reverse proxies, and over HTTPS. [#924](https://github.com/fsprojects/FSharp.Formatting/issues/924)
 * Search dialog now auto-focuses the search input when opened, clears on close, and can be triggered with `Ctrl+K` / `Cmd+K` in addition to `/`.
 * Add `dotnet fsdocs convert` command to convert a single `.md`, `.fsx`, or `.ipynb` file to HTML (or another output format) without building a full documentation site. [#811](https://github.com/fsprojects/FSharp.Formatting/issues/811)
 * `fsdocs convert` now accepts the input file as a positional argument (e.g. `fsdocs convert notebook.ipynb -o notebook.html`). [#1019](https://github.com/fsprojects/FSharp.Formatting/pull/1019)

src/fsdocs-tool/BuildCommand.fs

@@ -819,11 +819,10 @@ module Serve =
     let refreshEvent = FSharp.Control.Event<string>()
 
     /// generate the script to inject into html to enable hot reload during development
-    let generateWatchScript (port: int) =
-        let tag =
-            """
+    let generateWatchScript () =
+        """
 <script type="text/javascript">
-    var wsUri = "ws://localhost:{{PORT}}/websocket";
+    var wsUri = "ws://" + window.location.host + "/websocket";
     function init()
     {
         websocket = new WebSocket(wsUri);
@@ -850,8 +849,6 @@ module Serve =
 </script>
 """
 
-        tag.Replace("{{PORT}}", string<int> port)
-
     let connectedClients = ConcurrentDictionary<WebSocket, unit>()
 
     let socketHandler (webSocket: WebSocket) (context: HttpContext) =
@@ -1560,9 +1557,15 @@ type CoreBuildOptions(watch) =
         // Adjust the user substitutions for 'watch' mode root
         let userRoot, userParameters =
             if watch then
-                let userRoot = sprintf "http://localhost:%d/" this.port_option
-
-                if userParametersDict.ContainsKey(ParamKeys.root) then
+                let userRoot =
+                    match this.root_override_option with
+                    | Some r -> r
+                    | None -> sprintf "http://localhost:%d/" this.port_option
+
+                if
+                    userParametersDict.ContainsKey(ParamKeys.root)
+                    && this.root_override_option.IsNone
+                then
                     printfn "ignoring user-specified root since in watch mode, root = %s" userRoot
 
                 let userParameters =
@@ -1873,7 +1876,7 @@ type CoreBuildOptions(watch) =
         let getLatestWatchScript () =
             if watch then
                 // if running in watch mode, inject hot reload script
-                [ ParamKeys.``fsdocs-watch-script``, Serve.generateWatchScript this.port_option ]
+                [ ParamKeys.``fsdocs-watch-script``, Serve.generateWatchScript () ]
             else
                 // otherwise, inject empty replacement string
                 [ ParamKeys.``fsdocs-watch-script``, "" ]
@@ -2325,6 +2328,9 @@ type CoreBuildOptions(watch) =
     abstract port_option: int
     default x.port_option = 0
 
+    abstract root_override_option: string option
+    default x.root_override_option = None
+
 /// Helpers for the <c>fsdocs convert</c> command.
 module private ConvertHelpers =
 
@@ -2741,3 +2747,12 @@ type WatchCommand() =
 
     [<Option("port", Required = false, Default = 8901, HelpText = "Port to serve content for http://localhost serving.")>]
     member val port = 8901 with get, set
+
+    override x.root_override_option = if x.root = "" then None else Some x.root
+
+    [<Option("root",
+             Required = false,
+             Default = "",
+             HelpText =
+                 "Override the root URL for generated pages. Useful for reverse proxies or GitHub Codespaces. E.g. --root / or --root https://example.com/docs/. When not set, defaults to http://localhost:<port>/.")>]
+    member val root = "" with get, set