suggested circleci fix

Author: WorldSEnder

plugins/tactics/hls-tactics-plugin.cabal

@@ -75,6 +75,7 @@ library
     , syb
     , text
     , transformers
+    , deepseq
 
   default-language: Haskell2010
 

plugins/tactics/src/Ide/Plugin/Tactic/Debug.hs

@@ -1,3 +1,7 @@
+{-# LANGUAGE BangPatterns     #-}
+{-# LANGUAGE CPP              #-}
+{-# LANGUAGE TypeApplications #-}
+
 module Ide.Plugin.Tactic.Debug
   ( unsafeRender
   , unsafeRender'
@@ -9,17 +13,36 @@ module Ide.Plugin.Tactic.Debug
   , traceMX
   ) where
 
+import Control.DeepSeq
+import Control.Exception
 import Debug.Trace
 import DynFlags (unsafeGlobalDynFlags)
 import Outputable hiding ((<>))
+import System.IO.Unsafe (unsafePerformIO)
+
+#if __GLASGOW_HASKELL__ >= 808
+import PlainPanic (PlainGhcException)
+type GHC_EXCEPTION = PlainGhcException
+#else
+import Panic (GhcException)
+type GHC_EXCEPTION = GhcException
+#endif
+
 
 ------------------------------------------------------------------------------
 -- | Print something
 unsafeRender :: Outputable a => a -> String
 unsafeRender = unsafeRender' . ppr
 
+
 unsafeRender' :: SDoc -> String
-unsafeRender' = showSDoc unsafeGlobalDynFlags
+unsafeRender' sdoc = unsafePerformIO $ do
+  let z = showSDoc unsafeGlobalDynFlags sdoc
+  -- We might not have unsafeGlobalDynFlags (like during testing), in which
+  -- case GHC panics. Instead of crashing, let's just fail to print.
+  !res <- try @GHC_EXCEPTION $ evaluate $ deepseq z z
+  pure $ either (const "<unsafeRender'>") id res
+{-# NOINLINE unsafeRender' #-}
 
 traceMX :: (Monad m, Show a) => String -> a -> m ()
 traceMX str a = traceM $ mappend ("!!!" <> str <> ": ") $ show a