Fix bug where --extraInstances ignored standalone instance declarations

CHANGELOG.md

@@ -1,6 +1,8 @@
 # 0.10.0
 * [#306](https://github.com/awakesecurity/proto3-suite/pull/306) 0.10.0: Use proto3-wire 1.5.0
   * Support proto3-wire 1.5 instead of proto3-wire 1.4.
+* Fix `--extraInstanceFile` to support standalone deriving declarations in
+  addition to regular instance declarations.
 
 # 0.9.5
 * [#305](https://github.com/awakesecurity/proto3-suite/pull/305) Avoid unpacked packed fields

README.md

@@ -138,10 +138,11 @@ Available options:
                            repeated, and paths will be searched in order; the
                            current directory is used if this option is not
                            provided)
-  --extraInstanceFile FILE Additional file to provide instances that would
-                           otherwise be generated. Can be used multiple times.
-                           Types for which instance overrides are given must be
-                           fully qualified.
+  --extraInstanceFile FILE Additional file to provide instance declarations or
+                           standalone deriving declarations that would otherwise
+                           be generated. Can be used multiple times. Types for
+                           which instance overrides are given must be fully
+                           qualified.
   --proto FILE             Path to input .proto file
   --out DIR                Output directory path where generated Haskell modules
                            will be written (directory is created if it does not

proto3-suite.cabal

@@ -1,6 +1,6 @@
 cabal-version:       2.2
 name:                proto3-suite
-version:             0.9.5
+version:             0.10.0
 synopsis:            A higher-level API to the proto3-wire library
 description:
   This library provides a higher-level API to <https://github.com/awakesecurity/proto3-wire the `proto3-wire` library>
@@ -29,6 +29,7 @@ data-files:
 extra-source-files:
   CHANGELOG.md,
   gen/.gitignore
+  tests/Test/Proto/Generate/CodeGen.hs
 
 flag dhall
   Description:   Turn on Dhall interpret and inject codegen

src/Proto3/Suite/DotProto/Generate.hs

@@ -34,6 +34,7 @@ module Proto3.Suite.DotProto.Generate
   , hsModuleForDotProto
   , renderHsModuleForDotProto
   , readDotProtoWithContext
+  , getExtraInstances
   ) where
 
 import           Control.Applicative
@@ -256,7 +257,7 @@ hsModuleForDotProto ::
   , (?stringType :: StringType)
   , (?typeLevelFormat :: Bool)
   ) =>
-  -- | Extra user-define instances that override default generated instances
+  -- | Extra user-defined instances and standalone deriving declarations that override default generated instances
   ([HsImportDecl], [HsDecl]) ->
   -- |
   DotProto ->
@@ -309,8 +310,9 @@ getExtraInstances logger (Turtle.encodeString -> extraInstanceFile) = do
     Nothing ->
       internalError (T.unpack "Error: Failed to parse instance file")
     Just (GHC.L _ m) -> do
-      let isInstDecl (GHC.L _ GHC.InstD{}) = True
-          isInstDecl _                     = False
+      let isInstDecl (GHC.L _ GHC.InstD{})  = True
+          isInstDecl (GHC.L _ GHC.DerivD{}) = True
+          isInstDecl _                      = False
       pure (GHC.hsmodImports m, filter isInstDecl (GHC.hsmodDecls m))
 
 -- | This very specific function will only work for the qualification on the very first type

test-files/extra_instances_deriving.hs

@@ -0,0 +1,13 @@
+{-# LANGUAGE StandaloneDeriving #-}
+
+module ExtraInstances where
+
+data Foo = Foo
+
+helper :: Int
+helper = 42
+
+instance Show Foo where
+  show _ = "Foo"
+
+deriving instance Eq Foo

tests/Main.hs

@@ -61,6 +61,7 @@ import           TestDhall
 
 import qualified Test.Proto.Generate.Name
 import qualified Test.Proto.Parse.Option
+import qualified Test.Proto.Generate.CodeGen
 import qualified Test.Proto.Interval
 import           Test.Proto.ToEncoder        (Iterator(Forward, Vector),
                                               Stripping(Keep, Strip), ToEncoder(..))
@@ -84,7 +85,7 @@ tests logger = testGroup "Tests"
   , Test.Proto.Generate.Name.testTree
   , Test.Proto.Parse.Option.testTree
   , Test.Proto.Interval.testTree
-
+  , Test.Proto.Generate.CodeGen.testTree
 #ifdef DHALL
   , dhallTests
 #endif

tests/Test/Proto/Generate/CodeGen.hs

@@ -0,0 +1,27 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Test.Proto.Generate.CodeGen (testTree) where
+
+import Control.Monad.Except (runExceptT)
+import Proto3.Suite.DotProto.Generate (getExtraInstances)
+import Proto3.Suite.Haskell.Parser (initLogger)
+import Test.Tasty
+import Test.Tasty.HUnit (assertEqual, assertFailure, testCase)
+
+testTree :: TestTree
+testTree = testGroup "Code generation"
+  [ extraInstanceParsing
+  ]
+
+-- | 'getExtraInstances' includes both regular instance declarations and
+-- standalone deriving declarations from extra instance files.
+extraInstanceParsing :: TestTree
+extraInstanceParsing =
+  testCase "getExtraInstances includes standalone deriving declarations" $ do
+    logger <- initLogger
+    result <- runExceptT $ getExtraInstances logger "test-files/extra_instances_deriving.hs"
+    case result of
+      Left err -> assertFailure (show err)
+      Right (_imports, decls) ->
+        assertEqual "expected 2 declarations (1 instance + 1 standalone deriving)"
+          2 (length decls)

tools/compile-proto-file/Main.hs

@@ -32,7 +32,7 @@ parseArgs = info (helper <*> parser) (fullDesc <> progDesc "Compiles a .proto fi
     extraInstances = many $ strOption $
       long "extraInstanceFile"
         <> metavar "FILE"
-        <> help "Additional file to provide instances that would otherwise be generated. Can be used multiple times. Types for which instance overrides are given must be fully qualified."
+        <> help "Additional file to provide instance declarations or standalone deriving declarations that would otherwise be generated. Can be used multiple times. Types for which instance overrides are given must be fully qualified."
 
     proto = strOption $
       long "proto"