add no-install flag for build to prevent automatic installation

app/Spago.hs

@@ -12,7 +12,7 @@ import qualified Turtle              as CLI
 
 import           Spago.Build         (BuildOptions (..), ExtraArg (..), ModuleName (..),
                                       NoBuild (..), SourcePath (..), TargetPath (..), Watch (..),
-                                      WithMain (..))
+                                      WithMain (..), NoInstall (..))
 import qualified Spago.Build
 import           Spago.GlobalCache   (CacheFlag (..))
 import           Spago.Messages      as Messages
@@ -114,13 +114,19 @@ parser = do
     force           = CLI.switch "force" 'f' "Overwrite any project found in the current directory"
     verbose         = CLI.switch "verbose" 'v' "Enable additional debug logging, e.g. printing `purs` commands"
     watchBool       = CLI.switch "watch" 'w' "Watch for changes in local files and automatically rebuild"
+    noInstallBool   = CLI.switch "no-install" 'n' "Don't run the automatic installation of packages"
     clearScreenBool = CLI.switch "clear-screen" 'l' "Clear the screen on rebuild (watch mode only)"
     noBuildBool     = CLI.switch "no-build" 's' "Skip build step"
     watch = do
       res <- watchBool
       pure $ case res of
         True  -> Watch
         False -> BuildOnce
+    noInstall = do
+      res <- noInstallBool
+      pure $ case res of
+        True  -> NoInstall
+        False -> DoInstall
     clearScreen = do
       res <- clearScreenBool
       pure $ case res of
@@ -150,7 +156,7 @@ parser = do
     packageName = CLI.arg (Just . PackageName) "package" "Specify a package name. You can list them with `list-packages`"
     packageNames = CLI.many $ CLI.arg (Just . PackageName) "package" "Package name to add as dependency"
     passthroughArgs = many $ CLI.arg (Just . ExtraArg) " ..any `purs compile` option" "Options passed through to `purs compile`; use -- to separate"
-    buildOptions = BuildOptions <$> limitJobs <*> cacheFlag <*> watch <*> clearScreen <*> sourcePaths <*> passthroughArgs
+    buildOptions = BuildOptions <$> limitJobs <*> cacheFlag <*> watch <*> clearScreen <*> sourcePaths <*> noInstall <*> passthroughArgs
     globalOptions = GlobalOptions <$> verbose
     packagesFilter =
       let wrap = \case

src/Spago/Build.hs

@@ -8,6 +8,7 @@ module Spago.Build
   , docs
   , Watch (..)
   , NoBuild (..)
+  , NoInstall (..)
   , BuildOptions (..)
   , Purs.ExtraArg (..)
   , Purs.ModuleName (..)
@@ -37,12 +38,16 @@ data Watch = Watch | BuildOnce
 --   or skip it, in the case of 'bundleApp' and 'bundleModule'.
 data NoBuild = NoBuild | DoBuild
 
+-- | Flag to skip the automatic installation of libraries on build
+data NoInstall = NoInstall | DoInstall
+
 data BuildOptions = BuildOptions
   { maybeLimit      :: Maybe Int
   , cacheConfig     :: Maybe GlobalCache.CacheFlag
   , shouldWatch     :: Watch
   , shouldClear     :: Watch.ClearScreen
   , sourcePaths     :: [Purs.SourcePath]
+  , noInstall       :: NoInstall
   , passthroughArgs :: [Purs.ExtraArg]
   }
 
@@ -63,7 +68,9 @@ build BuildOptions{..} maybePostBuild = do
   echoDebug "Running `spago build`"
   config@Config.Config{ packageSet = PackageSet.PackageSet{..}, ..} <- Config.ensureConfig
   deps <- Packages.getProjectDeps config
-  Fetch.fetchPackages maybeLimit cacheConfig deps packagesMinPursVersion
+  case noInstall of
+    DoInstall -> Fetch.fetchPackages maybeLimit cacheConfig deps packagesMinPursVersion
+    NoInstall -> pure ()
   let projectGlobs = configSourcePaths <> sourcePaths
       allGlobs = Packages.getGlobs deps <> projectGlobs
       buildAction = do

test/SpagoSpec.hs

@@ -133,14 +133,22 @@ spec = around_ setup $ do
       mv "src/Main.purs" "another_source_path/Main.purs"
       spago ["build", "--path", "another_source_path/*.purs"] >>= shouldBeSuccess
 
+    it "Spago should not install packages when passing the --no-install flag" $ do
+
+      spago ["init"] >>= shouldBeSuccess
+      spago ["build", "--no-install"] >>= shouldBeFailure
+      spago ["install"] >>= shouldBeSuccess
+      spago ["build", "--no-install"] >>= shouldBeSuccess
+
     it "Spago should add sources to config when key is missing" $ do
 
       configV1 <- readFixture "spago-configV1.dhall"
       spago ["init"] >>= shouldBeSuccess
       -- Replace initial config with the old config format (without 'sources')
+      mv "spago.dhall" "spago-old.dhall"
       writeTextFile "spago.dhall" configV1
 
-      spago ["build"] >>= shouldBeSuccess
+      spago ["install"] >>= shouldBeSuccess
       mv "spago.dhall" "spago-configV2.dhall"
       checkFixture "spago-configV2.dhall"