Test with GHC 9.0 and Stack (#1351)

* Test with GHC 9.0 and Stack
* stack-9.0.yaml: use lts-19.10
* IHaskell.Eval.Util: use `nub` when comparing package flags

.github/workflows/ci.yml

@@ -43,6 +43,7 @@ jobs:
           - stack-yaml: 'stack-8.6.yaml'
           - stack-yaml: 'stack-8.8.yaml'
           - stack-yaml: 'stack.yaml'
+          - stack-yaml: 'stack-9.0.yaml'
 
     steps:
       - uses: actions/checkout@v2

src/IHaskell/Eval/Util.hs

@@ -265,7 +265,8 @@ setFlags ext = do
 #else
       allWarns = map unLoc warnings ++
 #endif
-                 ["-package not supported yet" | packageFlags flags /= packageFlags flags0]
+        -- Stack appears to duplicate package flags, so we use `nub` to work around this
+        ["-package not supported yet" | nub (packageFlags flags) /= nub (packageFlags flags0)]
       warnErrs = map ("Warning: " ++) allWarns
   return $ noParseErrs ++ warnErrs
 

stack-9.0.yaml

@@ -1,5 +1,5 @@
 # the GHC version of this resolver needs to match the GHC version in Dockerfile
-resolver: lts-19.3
+resolver: lts-19.10
 #allow-newer: true
 
 flags: {}