Allow verify(-set) to work with alternate backends

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+Other improvements:
+- Allow `verify` and `verify-set` to work with alternate backends (when run in the context
+  of a `spago.dhall` with `backend` set)
+
 ## [0.19.1] - 2021-02-22
 
 Bugfixes:

src/Spago/Command/Verify.hs

@@ -53,7 +53,7 @@ verify chkModsUniq maybePackage = do
           quotedName = surroundQuote $ packageName name
       Fetch.fetchPackages deps
       logInfo $ display $ "Verifying package " <> quotedName
-      Purs.compile globs []
+      compile globs
       logInfo $ display $ "Successfully verified " <> quotedName
 
     compileEverything :: RIO env ()
@@ -63,5 +63,19 @@ verify chkModsUniq maybePackage = do
           globs = Packages.getGlobs deps Packages.DepsOnly []
       Fetch.fetchPackages deps
       logInfo "Compiling everything (will fail if module names conflict)"
-      Purs.compile globs []
-      logInfo "Successfully compiled everything"
+      compile globs
+      logInfo "Successfully compiled everything"
+
+    compile :: [SourcePath] -> RIO env ()
+    compile globs = do
+      config <- view (the @(Maybe Config))
+      case config >>= alternateBackend of
+        Nothing ->
+          Purs.compile globs []
+        Just backend -> do
+          Purs.compile globs [ PursArg "--codegen", PursArg "corefn" ]
+          let backendCmd = backend -- In future there will be some arguments here
+          logDebug $ "Running command `" <> display backendCmd <> "`"
+          shell backendCmd empty >>= \case
+            ExitSuccess   -> pure ()
+            ExitFailure n -> die [ "Backend " <> displayShow backend <> " exited with error:" <> repr n ]

src/Spago/Env.hs

@@ -64,13 +64,15 @@ type HasEnv env =
   )
 
 type HasConfig env = ( HasType Config env, HasPackageSet env )
+type HasMaybeConfig env = ( HasType (Maybe Config) env, HasPackageSet env )
 
 type HasVerifyEnv env =
   ( HasLogFunc env
   , HasJobs env
   , HasGlobalCache env
   , HasPurs env
   , HasPackageSet env
+  , HasMaybeConfig env
   )
 
 type HasPublishEnv env =
@@ -108,6 +110,7 @@ data VerifyEnv = VerifyEnv
   , envGlobalCache :: !GlobalCache
   , envPursCmd :: !PursCmd
   , envPackageSet :: !PackageSet
+  , envConfig :: !(Maybe Config)
   } deriving (Generic)
 
 data InstallEnv = InstallEnv

src/Spago/RunEnv.hs

@@ -96,6 +96,7 @@ withVerifyEnv usePsa app = do
   Env{..} <- getEnv
   envPursCmd <- getPurs usePsa
   envPackageSet <- getPackageSet
+  envConfig <- hush <$> Config.ensureConfig 
   runRIO VerifyEnv{..} app
 
 withPublishEnv