From 5adc8c7429bd7a9269d03dc8ca197741038cf679 Mon Sep 17 00:00:00 2001
From: Brent Yorgey <byorgey@gmail.com>
Date: Sat, 13 Jan 2024 18:14:29 -0600
Subject: [PATCH] Child robots only inherit their parent's `displayAttr`
 (#1722)

Fixes #1693.  It's not necessarily appropriate to copy the entire `Display` record.  So instead, we explicitly list the fields that should be inherited.  For now, it is only `displayAttr`, but we could add `invisible` in the future (see #1670, #1663).

Tested to make sure behavior is preserved with:
```
scripts/play.sh -i scenarios/Challenges/Ranching/beekeeping.yaml --autoplay
```
---
 src/swarm-engine/Swarm/Game/Step/Const.hs | 5 ++++-
 src/swarm-util/Swarm/Util/Lens.hs         | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/swarm-engine/Swarm/Game/Step/Const.hs b/src/swarm-engine/Swarm/Game/Step/Const.hs
index 65799b99b..ef929f6ed 100644
--- a/src/swarm-engine/Swarm/Game/Step/Const.hs
+++ b/src/swarm-engine/Swarm/Game/Step/Const.hs
@@ -91,6 +91,7 @@ import Swarm.Language.Value
 import Swarm.Log
 import Swarm.Util hiding (both)
 import Swarm.Util.Effect (throwToMaybe)
+import Swarm.Util.Lens (inherit)
 import Witch (From (from), into)
 import Prelude hiding (Applicative (..), lookup)
 
@@ -1052,7 +1053,9 @@ execConst runChildProg c vs s k = do
               ( ((r ^. robotOrientation) >>= \dir -> guard (dir /= zero) >> return dir)
                   ? north
               )
-              ((r ^. robotDisplay) & invisible .~ False)
+              ( defaultRobotDisplay
+                  & inherit displayAttr (r ^. robotDisplay)
+              )
               (In cmd e s [FExec])
               []
               []
diff --git a/src/swarm-util/Swarm/Util/Lens.hs b/src/swarm-util/Swarm/Util/Lens.hs
index 19f5659aa..e9230252f 100644
--- a/src/swarm-util/Swarm/Util/Lens.hs
+++ b/src/swarm-util/Swarm/Util/Lens.hs
@@ -5,9 +5,11 @@
 module Swarm.Util.Lens (
   makeLensesNoSigs,
   makeLensesExcluding,
+  inherit,
 ) where
 
 import Control.Lens (
+  Lens',
   generateSignatures,
   lensField,
   lensRules,
@@ -16,6 +18,7 @@ import Control.Lens (
   (%~),
   (&),
   (.~),
+  (^.),
  )
 import Language.Haskell.TH (DecsQ)
 import Language.Haskell.TH.Syntax (Name)
@@ -40,3 +43,7 @@ makeLensesExcluding exclude =
         & lensField . mapped . mapped %~ \fn n ->
           if n `elem` exclude then [] else fn n
     )
+
+-- | Copy a given field from one record to another.
+inherit :: Lens' s a -> s -> (s -> s)
+inherit field parent child = child & field .~ (parent ^. field)