Revert "remove windows special behavior by using spawn and unref"

This reverts commit 31c8b9e.

Author: jkrumbiegel

src/execute/julia.ts

@@ -241,23 +241,64 @@ async function startOrReuseJuliaServer(
     info("Starting julia control server process. This might take a while...");
     await ensureQuartoNotebookRunnerEnvironment(options);
 
-    const command = new Deno.Command(options.julia_cmd, {
-      args: [
-        "--startup-file=no",
-        resourcePath("julia/start_quartonotebookrunner_detached.jl"),
-        options.julia_cmd,
-        juliaRuntimeDir(),
-        resourcePath("julia/quartonotebookrunner.jl"),
-        transportFile,
-      ],
-    });
-    trace(
-      options,
-      "Starting detached julia server through julia, once transport file exists, server should be running.",
-    );
-    // unref seems to be needed to let deno exit in the tests after having spawned the julia process
-    // that creates the detached child process
-    command.spawn().unref();
+    // We need to spawn the julia server in its own process that can outlive quarto.
+    // Apparently, `run(detach(cmd))` in julia does not do that reliably on Windows,
+    // at least deno never seems to recognize that the spawning julia process has finished,
+    // presumably because it waits for the active child process to exit. This makes the
+    // tests on windows hang forever if we use the same launching mechanism as for Unix systems.
+    // So we utilize powershell instead which can start completely detached processes with
+    // the Start-Process commandlet.
+    if (Deno.build.os === "windows") {
+      const command = new Deno.Command(
+        "PowerShell",
+        {
+          args: [
+            "-Command",
+            "Start-Process",
+            options.julia_cmd,
+            "-ArgumentList",
+            // string array argument list, each element but the last must have a "," element after
+            "--startup-file=no",
+            ",",
+            `--project=${juliaRuntimeDir()}`,
+            ",",
+            resourcePath("julia/quartonotebookrunner.jl"),
+            ",",
+            transportFile,
+            // end of string array
+            "-WindowStyle",
+            "Hidden",
+          ],
+        },
+      );
+      trace(
+        options,
+        "Starting detached julia server through powershell, once transport file exists, server should be running.",
+      );
+      const result = command.outputSync();
+      if (!result.success) {
+        throw new Error(new TextDecoder().decode(result.stderr));
+      }
+    } else {
+      const command = new Deno.Command(options.julia_cmd, {
+        args: [
+          "--startup-file=no",
+          resourcePath("julia/start_quartonotebookrunner_detached.jl"),
+          options.julia_cmd,
+          juliaRuntimeDir(),
+          resourcePath("julia/quartonotebookrunner.jl"),
+          transportFile,
+        ],
+      });
+      trace(
+        options,
+        "Starting detached julia server through julia, once transport file exists, server should be running.",
+      );
+      const result = command.outputSync();
+      if (!result.success) {
+        throw new Error(new TextDecoder().decode(result.stderr));
+      }
+    }
   } else {
     trace(
       options,