Disable deriving-defaults per file (#8684)

Disabling it per target works nicely for compilation but it gets
annoying in ghci since the warnings are still triggered. We could
disable it everywhere but I think the warning is generally useful. I
tried patching proto3-suite to use DerivingStrategies but that doesn’t
work because haskell-src is dead and doesn’t support it. So for now
adding it to the per-file list seems like the best option.

changelog_begin
changelog_end

3rdparty/haskell/BUILD.bazel

@@ -36,7 +36,6 @@ da_haskell_library(
         "//ledger-api/grpc-definitions:google-protobuf-haskellpb-sources",
         "//ledger-api/grpc-definitions:google-rpc-haskellpb-sources",
     ],
-    compiler_flags = ["-Wno-deriving-defaults"],
     hackage_deps = [
         "base",
         "bytestring",

bazel-haskell-deps.bzl

@@ -216,6 +216,8 @@ haskell_cabal_library(
         sha256 = "b294ff0fe24c6c256dc8eca1d44c2a9a928b9a1bc70ddce6a1d059499edea119",
         strip_prefix = "proto3-suite-0af901f9ef3b9719e08eae4fab8fd700d6c8047a",
         urls = ["https://github.com/awakesecurity/proto3-suite/archive/0af901f9ef3b9719e08eae4fab8fd700d6c8047a.tar.gz"],
+        patches = ["@com_github_digital_asset_daml//bazel_tools:haskell_proto3_suite_deriving_defaults.patch"],
+        patch_args = ["-p1"],
     )
 
     http_archive(

bazel_tools/haskell_proto3_suite_deriving_defaults.patch

@@ -0,0 +1,21 @@
+GHC 8.10 enables -Wderiving-defaults as part of -Wall.
+It’s a useful warning so we want to keep it. However,
+proto3-suite generates code that triggers this warning.
+Now ideally, we would just switch proto3-suite over to
+DerivingStrategies but unfortunately haskell-src, the library
+used to generate the Haskell source, does not support that.
+So instead, we disable the warning on a per file basis.
+The warning only exists in GHC >= 8.10 so we cannot
+upstream this atm.
+diff --git a/src/Proto3/Suite/DotProto/Generate.hs b/src/Proto3/Suite/DotProto/Generate.hs
+index 566b8a9..fae46a4 100644
+--- a/src/Proto3/Suite/DotProto/Generate.hs
++++ b/src/Proto3/Suite/DotProto/Generate.hs
+@@ -127,6 +127,7 @@ renderHsModuleForDotProto extraInstanceFiles dotProto importCtxt = do
+       {-# OPTIONS_GHC -fno-warn-unused-imports #-}
+       {-# OPTIONS_GHC -fno-warn-name-shadowing #-}
+       {-# OPTIONS_GHC -fno-warn-unused-matches #-}
++      {-# OPTIONS_GHC -Wno-deriving-defaults #-}
+ 
+       -- | Generated by Haskell protocol buffer compiler. DO NOT EDIT!
+     |]

compiler/repl-service/protos/BUILD.bazel

@@ -67,7 +67,6 @@ genrule(
 da_haskell_library(
     name = "repl_service_haskell_proto",
     srcs = [":repl_service_haskell_proto_src"],
-    compiler_flags = ["-Wno-deriving-defaults"],
     hackage_deps = [
         "base",
         "bytestring",

daml-lf/archive/BUILD.bazel

@@ -81,7 +81,6 @@ da_haskell_library(
     srcs = [":daml_lf_dev_archive_haskell_proto_src"],
     compiler_flags = [
         "-O0",
-        "-Wno-deriving-defaults",
     ],  # disable optimization as this is otherwise way too slow to compile.
     hackage_deps = [
         "base",

ledger-api/grpc-definitions/BUILD.bazel

@@ -225,7 +225,6 @@ da_haskell_library(
     ],
     compiler_flags = [
         "-O0",
-        "-Wno-deriving-defaults",
     ],
     hackage_deps = [
         "base",