Musical chairs, part 1: add warnings and aliases

Cabal/Distribution/Simple/Setup.hs

@@ -60,6 +60,7 @@ module Distribution.Simple.Setup (
   buildOptions, haddockOptions, installDirsOptions,
   programDbOptions, programDbPaths',
   programConfigurationOptions, programConfigurationPaths',
+  programFlagsDescription,
   splitArgs,
 
   defaultDistPref, optionDistPref,

Cabal/doc/nix-local-build-overview.rst

@@ -2,8 +2,13 @@ Nix-style Local Builds
 ======================
 
 Nix-style local builds are a new build system implementation inspired by Nix.
-The Nix-style local build system is commonly called "new-build" for short after the ``cabal new-*`` family of commands that control it.
-However those names are only temporary until Nix-style local builds becomes the default.
+The Nix-style local build system is commonly called "new-build" for short
+after the ``cabal new-*`` family of commands that control it. However, those
+names are only temporary until Nix-style local builds become the default.
+This is expected to happen soon. For those who do not wish to use the new
+functionality, the classic project style will not be removed immediately,
+but these legacy commands will require the usage of the ``v1-`` prefix as of
+Cabal 3.0 and will be removed in a future release.
 
 Nix-style local builds combine the best of non-sandboxed and sandboxed Cabal:
 

cabal-install/Distribution/Client/CmdLegacy.hs

@@ -0,0 +1,109 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE ViewPatterns #-}
+module Distribution.Client.CmdLegacy (legacyCmd) where
+
+import Prelude ()
+import Distribution.Client.Compat.Prelude
+
+import qualified Distribution.Client.Setup as Client
+import qualified Distribution.Simple.Setup as Setup
+import Distribution.Simple.Command
+import Distribution.Simple.Utils
+    ( warn )
+import Distribution.Verbosity 
+    ( Verbosity, normal )
+
+import qualified Data.Text as T
+
+-- Duplicated code (it's identical to Main.regularCmd), but makes things cleaner
+-- and lets me keep how this happens a dirty little secret.
+makeCmd :: CommandUI flags -> (flags -> [String] -> action) -> CommandSpec action
+makeCmd ui action = CommandSpec ui ((flip commandAddAction) action) NormalCommand
+
+deprecationNote :: String -> String
+deprecationNote cmd =
+    "The " ++ cmd ++ " command is a part of the legacy v1 style of cabal usage.\n\n" ++
+
+    "Please switch to using either the new project style or the legacy v1-" ++ cmd ++ "\n" ++
+    "alias as new-style projects will become the default in the next version of\n" ++
+    "cabal-install. Please file a bug if you cannot replicate a working v1- use\n" ++
+    "case with the new-style commands.\n"
+
+legacyNote :: String -> String
+legacyNote cmd =
+    "The v1-" ++ cmd ++ " command is a part of the legacy v1 style of cabal usage.\n\n" ++
+
+    "It is a legacy feature and will be removed in a future release of cabal-install.\n" ++
+    "Please file a bug if you cannot replicate a working v1- use case with the new-style\n" ++
+    "commands.\n"
+
+--
+
+class HasVerbosity a where 
+    verbosity :: a -> Verbosity
+
+instance HasVerbosity (Setup.Flag Verbosity) where
+    verbosity = Setup.fromFlagOrDefault normal
+
+instance (HasVerbosity a) => HasVerbosity (a, b) where
+    verbosity (a, _) = verbosity a
+
+instance (HasVerbosity b) => HasVerbosity (a, b, c) where
+    verbosity (_ , b, _) = verbosity b
+
+instance (HasVerbosity a) => HasVerbosity (a, b, c, d) where
+    verbosity (a, _, _, _) = verbosity a
+
+instance HasVerbosity Setup.BuildFlags where
+    verbosity = verbosity . Setup.buildVerbosity
+
+instance HasVerbosity Setup.ConfigFlags where
+    verbosity = verbosity . Setup.configVerbosity
+
+instance HasVerbosity Setup.ReplFlags where
+    verbosity = verbosity . Setup.replVerbosity
+
+instance HasVerbosity Client.FreezeFlags where
+    verbosity = verbosity . Client.freezeVerbosity
+
+instance HasVerbosity Setup.HaddockFlags where
+    verbosity = verbosity . Setup.haddockVerbosity
+
+instance HasVerbosity Client.ExecFlags where
+    verbosity = verbosity . Client.execVerbosity
+
+instance HasVerbosity Client.UpdateFlags where
+    verbosity = verbosity . Client.updateVerbosity
+
+instance HasVerbosity Setup.CleanFlags where
+    verbosity = verbosity . Setup.cleanVerbosity
+
+--
+
+legacyCmd :: (HasVerbosity flags) => CommandUI flags -> (flags -> [String] -> globals -> IO action) -> [CommandSpec (globals -> IO action)]
+legacyCmd origUi@CommandUI{..} action = [makeCmd legUi action, makeCmd depUi depAction]
+    where
+        legacyMsg = T.unpack . T.replace "v1-" "" . T.pack
+
+        depNote = deprecationNote commandName
+        legNote = legacyNote commandName
+
+        depAction flags extra globals = warn (verbosity flags) (depNote ++ "\n") >> action flags extra globals
+
+        legUi = origUi 
+            { commandName = "v1-" ++ commandName
+            , commandNotes = Just $ \pname -> case commandNotes of
+                Just notes -> notes pname ++ "\n" ++ legNote
+                Nothing -> legNote
+            }
+
+        depUi = origUi
+            { commandName = legacyMsg commandName
+            , commandUsage = legacyMsg . commandUsage
+            , commandDescription = (legacyMsg .) <$> commandDescription
+            , commandNotes = Just $ \pname -> case commandNotes of
+                Just notes -> legacyMsg (notes pname) ++ "\n" ++ depNote
+                Nothing -> depNote
+            }