Extra GHC flags on CI, and do not error on deprecations

nix/overlay.nix

@@ -5,7 +5,29 @@ with final.haskell.lib;
   autodocodecPackages =
     let
       autodocodecPkg = name:
-        doBenchmark (buildStrictly (final.haskellPackages.callCabal2nixWithOptions name (final.gitignoreSource (../. + "/${name}")) "--no-hpack" { }));
+        buildStrictly (
+          overrideCabal (final.haskellPackages.callCabal2nixWithOptions name (final.gitignoreSource (../. + "/${name}")) "--no-hpack" { })
+            (old: {
+              doBenchmark = true;
+              configureFlags = (old.configureFlags or [ ]) ++ [
+                # Optimisations
+                "--ghc-options=-O2"
+                # Extra warnings
+                "--ghc-options=-Wall"
+                "--ghc-options=-Wincomplete-uni-patterns"
+                "--ghc-options=-Wincomplete-record-updates"
+                "--ghc-options=-Wpartial-fields"
+                "--ghc-options=-Widentities"
+                "--ghc-options=-Wredundant-constraints"
+                "--ghc-options=-Wcpp-undef"
+                "--ghc-options=-Werror"
+                "--ghc-options=-Wno-deprecations"
+              ];
+              # Ugly hack because we can't just add flags to the 'test' invocation.
+              # Show test output as we go, instead of all at once afterwards.
+              testTarget = (old.testTarget or "") + " --show-details=direct";
+            })
+        );
     in
     final.lib.genAttrs [
       "autodocodec"

stack.yaml

@@ -36,5 +36,8 @@ extra-deps:
     - sydtest-discover
 - envparse-0.4.1@sha256:989902e6368532548f61de1fa245ad2b39176cddd8743b20071af519a709ce30,2842
 
+ghc-options:
+  "$locals": -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates -Wpartial-fields -Widentities -Wredundant-constraints -Wcpp-undef
+
 nix:
   shell-file: shell.nix