Add missing Haddock documentation.

Author: mpilgrem

src/Stack/Build/ExecuteEnv.hs

@@ -115,6 +115,8 @@ import           System.Environment ( lookupEnv )
 import           System.FileLock
                    ( SharedExclusive (..), withFileLock, withTryFileLock )
 
+-- | Type representing environments in which the @Setup.hs@ commands of Cabal
+-- (the library) can be executed.
 data ExecuteEnv = ExecuteEnv
   { installLock    :: !(MVar ())
   , buildOpts      :: !BuildOpts

src/Stack/Nix.hs

@@ -49,6 +49,7 @@ instance Exception NixException where
     "Error: [S-7384]\n"
     ++ "Cannot determine project root directory."
 
+-- | Execute @nix-shell@, replacing the current process.
 runShellAndExit :: RIO Config void
 runShellAndExit = do
   inContainer <- getInContainer -- TODO we can probably assert that this is False based on Stack.Runners now
@@ -162,9 +163,10 @@ escape str =
   ++ foldr (\c -> if c == '\'' then ("'\"'\"'"++) else (c:)) "" str
   ++ "'"
 
--- | Command-line argument for "nix"
+-- | Command-line argument for "nix".
 nixCmdName :: String
 nixCmdName = "nix"
 
+-- | Command-line option to show only @--nix-*@ options.
 nixHelpOptName :: String
 nixHelpOptName = nixCmdName ++ "-help"

src/Stack/Options/NixParser.hs

@@ -3,7 +3,10 @@
 
 {-|
 Module      : Stack.Options.NixParser
+Description : Parser for options for Nix integration.
 License     : BSD-3-Clause
+
+Parser for Stack's command line options for Nix integration.
 -}
 
 module Stack.Options.NixParser
@@ -23,6 +26,7 @@ import           Stack.Options.Utils ( hideMods )
 import           Stack.Prelude
 import           Stack.Types.Nix ( NixOptsMonoid (..) )
 
+-- | Parser for Stack's command line options for integration with Nix.
 nixOptsParser :: Bool -> Parser NixOptsMonoid
 nixOptsParser hide0 = overrideActivation <$>
   (   NixOptsMonoid