From 29a606951d70a8417a70c456a1cc87d73909ce00 Mon Sep 17 00:00:00 2001
From: Alex Archambault <alexandre.archambault@gmail.com>
Date: Mon, 17 Feb 2025 14:59:47 +0100
Subject: [PATCH] Tweak doc watch mode handling

---
 build.sc              | 20 ++++++++++++++++++--
 docs/pages/develop.md |  9 ++-------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/build.sc b/build.sc
index 36a9aa78..326b7806 100644
--- a/build.sc
+++ b/build.sc
@@ -511,9 +511,25 @@ object docs extends ScalaModule {
   }
   def mkdocsServe() = T.command[Unit] {
     mdoc()()
-    os.proc("mkdocs", "serve", mkdocsConfigArgs())
-      .call(cwd = millModuleBasePath.value, stdin = os.Inherit, stdout = os.Inherit)
+    val docsDir = T.workspace / "docs"
+    val serveProc = os.proc("mkdocs", "serve", mkdocsConfigArgs())
+      .spawn(cwd = docsDir, stdin = os.Inherit, stdout = os.Inherit)
+    val mdocProc = os.proc(
+      "java",
+      "-cp",
+      compileClasspath().map(_.path).mkString(File.pathSeparator),
+      mainClass().getOrElse(???),
+      mdocWatchArgs().value
+    )
+      .spawn(cwd = docsDir, stdin = os.Inherit, stdout = os.Inherit)
+
+    while (serveProc.isAlive && mdocProc.isAlive)
+      Thread.sleep(1000L)
 
+    val serveRetCode = serveProc.waitFor()
+    val mdocRetCode  = mdocProc.waitFor()
+    if (serveRetCode != 0 || mdocRetCode != 0)
+      sys.error(s"Got exit code $serveRetCode for mkdocs serve and $mdocRetCode for mdoc")
     ()
   }
   def mkdocsBuild() = T.command[Unit] {
diff --git a/docs/pages/develop.md b/docs/pages/develop.md
index d0089781..074ae997 100644
--- a/docs/pages/develop.md
+++ b/docs/pages/develop.md
@@ -4,14 +4,9 @@
 
 ### Watch mode
 
-In a first terminal, run
+Run
 ```text
-$ ./mill -i -w docs.mdocWatch
-```
-
-Leave it running, and run in a second terminal
-```text
-$ ./mill -i -w docs.mkdocsServe
+$ ./mill -i docs.mkdocsServe
 ```
 
 Then open the URL printed in the console in your browser (it should be