docs: refactor serve-docs; add nix run .#docs

Refactor `serve-docs` using `makeWrapper`, make it available as a
`serve-docs` package and as the `docs` "app".

This means `nix build .#docs` will build the docs while `nix run .#docs`
will run the server.

docs/default.nix

@@ -132,5 +132,9 @@ lib.fix (
       inherit evaledModules transformOptions;
       inherit (self) search lib-docs;
     };
+
+    serve-docs = pkgs.callPackage ./server {
+      inherit (self) docs;
+    };
   }
 )

docs/server/default.nix

@@ -0,0 +1,19 @@
+{
+  lib,
+  runCommand,
+  makeBinaryWrapper,
+  python3,
+  docs,
+}:
+runCommand "serve-docs"
+  {
+    nativeBuildInputs = [ makeBinaryWrapper ];
+    meta.mainProgram = "server";
+  }
+  ''
+    mkdir -p $out/bin
+    makeWrapper ${lib.getExe python3} \
+        $out/bin/server \
+        --add-flags ${./server.py} \
+        --chdir ${docs}
+  ''

flake/dev/devshell.nix

@@ -101,14 +101,7 @@
               help = "Build and serve documentation locally";
               command = ''
                 echo -e "=> Building nixvim documentation...\n"
-
-                doc_derivation=$(${nix} build .#docs --no-link --print-out-paths)
-
-                echo -e "\n=> Documentation successfully built ('$doc_derivation')"
-
-                echo -e "\n=> You can then open your browser to view the doc\n"
-
-                (cd "$doc_derivation"/share/doc && ${pkgs.lib.getExe pkgs.python3} ${./server.py})
+                nix run .#docs
               '';
             }
             {

flake/packages.nix

@@ -7,11 +7,15 @@
 {
   perSystem =
     {
+      config,
       inputs',
       system,
       ...
     }:
     {
+      # Run the docs server when using `nix run .#docs`
+      apps.docs.program = config.packages.serve-docs;
+
       packages = import ../docs {
         nixvim = self;
         inherit helpers;