make halted robots immediately wake up

data/scenarios/Testing/00-ORDER.txt

@@ -72,3 +72,4 @@ Achievements
 2086-structure-palette.yaml
 2239-custom-entity.yaml
 2240-overridden-entity-capabilities.yaml
+2253-halt-waiting.yaml

data/scenarios/Testing/2253-halt-waiting.yaml

@@ -0,0 +1,27 @@
+version: 1
+name: Halt a waiting robot
+description: |
+  Calling `halt` on a waiting robot should make it immediately idle,
+  so it can e.g. be `reprogram`med
+creative: true
+objectives:
+  - goal:
+      - Get some gold
+    condition: |
+      as base { has "gold" };
+robots:
+  - name: base
+    dir: north
+    devices:
+      - logger
+solution: |
+  r <- build {move; wait 10000};
+  wait 2;
+  halt r; wait 1; reprogram r {create "gold"; give base "gold"}
+world:
+  dsl: |
+    {grass}
+  palette:
+    'B': [grass, null, base]
+  map: |
+    B

src/swarm-engine/Swarm/Game/Step/Const.hs

@@ -893,9 +893,10 @@ execConst runChildProg c vs s k = do
             omni <- isPrivilegedBot
             case omni || not (target ^. systemRobot) of
               True -> zoomRobots $ do
-                -- Cancel its CESK machine, and put it to sleep.
+                -- Cancel its CESK machine, and wake it up to ensure
+                -- it can do cleanup + run to completion.
                 robotMap . at targetID . _Just . machine %= cancel
-                sleepForever targetID
+                activateRobot targetID
                 return $ mkReturn ()
               False -> throwError $ cmdExn c ["You are not authorized to halt that robot."]
       _ -> badConst

test/integration/Main.hs

@@ -507,6 +507,7 @@ testScenarioSolutions rs ui key =
         assertBool "Error message should mention tank treads but not treads" $
           not (any ("- treads" `T.isInfixOf`) msgs)
             && any ("- tank treads" `T.isInfixOf`) msgs
+    , testSolution Default "Testing/2253-halt-waiting"
     ]
  where
   -- expectFailIf :: Bool -> String -> TestTree -> TestTree