From 7f9971512de566d940b92703594fb71e2c95eb1f Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Mon, 8 Jul 2024 21:13:49 +0100
Subject: [PATCH] a6-rc-up-tree: handle blocked deps, exit 1 if nothing started

---
 pkgs/s6-rc-up-tree/default.nix       | 14 ++++++++++--
 pkgs/s6-rc-up-tree/s6-rc-up-tree.fnl | 33 ++++++++++++++++++++--------
 pkgs/s6-rc-up-tree/scripts/s6-rc     |  1 +
 pkgs/s6-rc-up-tree/scripts/s6-rc-db  | 14 ++++++++++--
 4 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/pkgs/s6-rc-up-tree/default.nix b/pkgs/s6-rc-up-tree/default.nix
index 529193a..e62f044 100644
--- a/pkgs/s6-rc-up-tree/default.nix
+++ b/pkgs/s6-rc-up-tree/default.nix
@@ -46,9 +46,19 @@ stdenv.mkDerivation {
 
     # started controlled rdepends are running, so starting them is harmless
 
-    # descendants which depend on a _different_ controlled service, which is down, don't start
+    # descendants which depend on a _different_ controlled service,
+    # which is down, don't start:
+    # Given:
+    #  - modeswitch is controlled
+    #  - atz is controlled
+    #  - atz => modeswitch
+    #  - ifconfig => atz
+    # Then: if atz is down, ifconfig should not start when modeswitch is started
+    fennelrepl ./test.fnl ${./test-services} modeswitch
+    expect "modeswitch"
 
     # descendants which depend on a _different_ controlled service, which is up, do start
-
+    ATZ=up fennelrepl ./test.fnl ${./test-services} modeswitch
+    expect "modeswitch atz ifconfig"
   '';
 }
diff --git a/pkgs/s6-rc-up-tree/s6-rc-up-tree.fnl b/pkgs/s6-rc-up-tree/s6-rc-up-tree.fnl
index 2ad8017..c73aafb 100644
--- a/pkgs/s6-rc-up-tree/s6-rc-up-tree.fnl
+++ b/pkgs/s6-rc-up-tree/s6-rc-up-tree.fnl
@@ -38,16 +38,31 @@
   (with-popen [h (.. "s6-rc -b -u change " name)]
     (print (h:read "*a"))))
 
+(fn keys [t]
+  (icollect [_ v (pairs t)] v))
+
 (fn run [dir]
   (let [service (. arg 1)
-        blocks (stopped-controlled-services (or dir "/run/services/controlled"))]
-    (print :service service :blocks (view blocks))
-    (each [_ s (ipairs (reverse-dependencies service))]
-      (print :dep s)
-      (when
-          (accumulate [start true
-                       _ dep (ipairs (dependencies s))]
-            (and start (or (= s service) (not (. blocks dep)))))
-        (start-service s)))))
+        blocks (doto
+                   (stopped-controlled-services (or dir "/run/services/controlled"))
+                 (tset service nil))
+        rdepends (reverse-dependencies service)
+        starts
+        (icollect [_ s (ipairs rdepends)]
+          (when
+              (accumulate [start true
+                           _ dep (ipairs (dependencies s))]
+                (and start (not (. blocks dep))))
+            s))]
+    (print "s6-rc-up-tree"
+           service
+           "blocks (" (table.concat (keys blocks) ", ") ")"
+           ;; "rdepends (" (table.concat rdepends ", ") ")"
+           "start (" (table.concat  starts ", ") ")")
+    (if (> (# starts) 0)
+        (each [_ s (ipairs starts)]
+          (start-service s))
+        (os.exit 1))))
+
 
 { : run }
diff --git a/pkgs/s6-rc-up-tree/scripts/s6-rc b/pkgs/s6-rc-up-tree/scripts/s6-rc
index 43f56ce..135b388 100755
--- a/pkgs/s6-rc-up-tree/scripts/s6-rc
+++ b/pkgs/s6-rc-up-tree/scripts/s6-rc
@@ -8,6 +8,7 @@ if [ "$1" = "-da" ]; then
 	echo wattle # controlled
 	echo wombat # controlled
 	echo turmeric # uncontrolled
+	test -n "$ATZ" || echo atz # uncontrolled
     fi
 fi
 if [ "$1" = "-u" ]; then
diff --git a/pkgs/s6-rc-up-tree/scripts/s6-rc-db b/pkgs/s6-rc-up-tree/scripts/s6-rc-db
index 2b8a1c1..392e3a3 100755
--- a/pkgs/s6-rc-up-tree/scripts/s6-rc-db
+++ b/pkgs/s6-rc-up-tree/scripts/s6-rc-db
@@ -9,6 +9,12 @@ reverse_deps(){
 	enables-wan)
 	    echo wattle # controlled
 	    ;;
+	modeswitch)
+	    reverse_deps atz
+	    ;;
+	atz)
+	    echo ifconfig
+	    ;;
     esac
 }
 
@@ -17,8 +23,12 @@ deps(){
     case "$1" in
 	rosemary)
 	    echo thyme;;
-	*)
-	    ;;
+	wattle)
+	    echo enables-wan;;
+	atz)
+	    echo modeswitch;;
+	ifconfig)
+	    deps atz;;
     esac
 }