Finish new-install

Cabal/Cabal.cabal

@@ -441,6 +441,7 @@ library
     Distribution.GetOpt
     Distribution.Lex
     Distribution.Utils.String
+    Distribution.Simple.GHC.EnvironmentParser
     Distribution.Simple.GHC.Internal
     Distribution.Simple.GHC.IPI642
     Distribution.Simple.GHC.IPIConvert

Cabal/ChangeLog.md

@@ -1,4 +1,5 @@
 # 2.4.0.0 (current development version)
+  * Add `readGhcEnvironmentFile` to parse GHC environment files.
   * Drop support for GHC 7.4, since it is out of our support window
     (and has been for over a year!)
   * Deprecate `preSDist`, `sDistHook`, and `postSDist` in service of 

Cabal/Distribution/Simple/GHC.hs

@@ -53,10 +53,15 @@ module Distribution.Simple.GHC (
         isDynamic,
         getGlobalPackageDB,
         pkgRoot,
-        -- * Constructing GHC environment files
+        -- * Constructing and deconstructing GHC environment files
         Internal.GhcEnvironmentFileEntry(..),
         Internal.simpleGhcEnvironmentFile,
+        Internal.renderGhcEnvironmentFile,
         Internal.writeGhcEnvironmentFile,
+        Internal.ghcPlatformAndVersionString,
+        readGhcEnvironmentFile,
+        parseGhcEnvironmentFile,
+        ParseErrorExc(..),
         -- * Version-specific implementation quirks
         getImplInfo,
         GhcImplInfo(..)
@@ -68,6 +73,7 @@ import Distribution.Compat.Prelude
 import qualified Distribution.Simple.GHC.IPI642 as IPI642
 import qualified Distribution.Simple.GHC.Internal as Internal
 import Distribution.Simple.GHC.ImplInfo
+import Distribution.Simple.GHC.EnvironmentParser
 import Distribution.PackageDescription.Utils (cabalBug)
 import Distribution.PackageDescription as PD
 import Distribution.InstalledPackageInfo (InstalledPackageInfo)

Cabal/Distribution/Simple/GHC/EnvironmentParser.hs

@@ -0,0 +1,51 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE RecordWildCards #-}
+module Distribution.Simple.GHC.EnvironmentParser 
+    ( parseGhcEnvironmentFile, readGhcEnvironmentFile, ParseErrorExc(..) ) where
+
+import Prelude ()
+import Distribution.Compat.Prelude
+
+import Distribution.Simple.Compiler
+    ( PackageDB(..) )
+import Distribution.Simple.GHC.Internal
+    ( GhcEnvironmentFileEntry(..) )
+import Distribution.Types.UnitId
+    ( mkUnitId )
+
+import Control.Exception
+    ( Exception, throwIO )
+import qualified Text.Parsec as P
+import Text.Parsec.String 
+    ( Parser, parseFromFile )
+
+parseEnvironmentFileLine :: Parser GhcEnvironmentFileEntry
+parseEnvironmentFileLine =      GhcEnvFileComment             <$> comment
+                       <|>      GhcEnvFilePackageId           <$> unitId
+                       <|>      GhcEnvFilePackageDb           <$> packageDb
+                       <|> pure GhcEnvFileClearPackageDbStack <*  clearDb
+    where
+        comment = P.string "--" *> P.many (P.noneOf "\r\n")
+        unitId = P.try $ P.string "package-id" *> P.spaces *> 
+            (mkUnitId <$> P.many1 (P.satisfy $ \c -> isAlphaNum c || c `elem` "-_.+"))
+        packageDb = (P.string "global-package-db"      *> pure GlobalPackageDB)
+                <|> (P.string "user-package-db"        *> pure UserPackageDB)
+                <|> (P.string "package-db" *> P.spaces *> (SpecificPackageDB <$> P.many1 (P.noneOf "\r\n") <* P.lookAhead P.endOfLine))
+        clearDb = P.string "clear-package-db"
+
+newtype ParseErrorExc = ParseErrorExc P.ParseError
+                      deriving (Show, Typeable)
+
+instance Exception ParseErrorExc
+
+parseGhcEnvironmentFile :: Parser [GhcEnvironmentFileEntry]
+parseGhcEnvironmentFile = parseEnvironmentFileLine `P.sepEndBy` P.endOfLine <* P.eof
+
+readGhcEnvironmentFile :: FilePath -> IO [GhcEnvironmentFileEntry]
+readGhcEnvironmentFile path =
+    either (throwIO . ParseErrorExc) return =<<
+        parseFromFile parseGhcEnvironmentFile path

Cabal/Distribution/Simple/GHC/Internal.hs

@@ -549,6 +549,7 @@ data GhcEnvironmentFileEntry =
                                       --   @user-package-db@ or
                                       --   @package-db blah/package.conf.d/@
      | GhcEnvFileClearPackageDbStack  -- ^ @clear-package-db@
+     deriving (Eq, Ord, Show)
 
 -- | Make entries for a GHC environment file based on a 'PackageDBStack' and
 -- a bunch of package (unit) ids.

Cabal/doc/nix-local-build.rst

@@ -173,8 +173,8 @@ A major deficiency in the current implementation of new-build is that
 there is no programmatic way to access the location of build products.
 The location of the build products is intended to be an internal
 implementation detail of new-build, but we also understand that many
-unimplemented features (e.g., ``new-install``) can only be reasonably
-worked around by accessing build products directly.
+unimplemented features can only be reasonably worked around by
+accessing build products directly.
 
 The location where build products can be found varies depending on the
 version of cabal-install:
@@ -461,8 +461,8 @@ invocations and bringing the project's executables into scope.
 cabal new-install
 -----------------
 
-``cabal new-install [FLAGS] PACKAGES`` builds the specified nonlocal packages
-and symlinks their executables in ``symlink-bindir`` (usually ``~/.cabal/bin``).
+``cabal new-install [FLAGS] PACKAGES`` builds the specified packages and 
+symlinks their executables in ``symlink-bindir`` (usually ``~/.cabal/bin``).
 
 For example this command will build the latest ``cabal-install`` and symlink
 its ``cabal`` executable:
@@ -471,8 +471,61 @@ its ``cabal`` executable:
 
     $ cabal new-install cabal-install
 
-For libraries and local packages see
-`Unsupported commands <#unsupported-commands>`__
+In addition, it's possible to use ``cabal new-install`` to install components
+of a local project. For example, with an up-to-date Git clone of the Cabal
+repository, this command will build cabal-install HEAD and symlink the
+``cabal`` executable:
+
+::
+
+    $ cabal new-install exe:cabal
+
+It is also possible to "install" libraries using the ``--lib`` flag. For 
+example, this command will build the latest Cabal library and install it:
+
+::
+
+    $ cabal new-install --lib Cabal
+
+This works by managing GHC environments. By default, it is writing to the
+global environment in ``~/.ghc/$ARCH-$OS-$GHCVER/environments/default``.
+``new-install`` provides the ``--package-env`` flag to control which of
+these environments is modified.
+
+This command will modify the environment file in the current directory:
+
+::
+
+    $ cabal new-install --lib Cabal --package-env .
+
+This command will modify the enviroment file in the ``~/foo`` directory:
+
+::
+
+    $ cabal new-install --lib Cabal --package-env foo/
+
+Do note that the results of the previous two commands will be overwritten by
+the use of other new-style commands, so it is not reccomended to use them inside
+a project directory.
+
+This command will modify the environment in the "local.env" file in the
+current directory:
+
+::
+
+    $ cabal new-install --lib Cabal --package-env local.env
+
+This command will modify the ``myenv`` named global environment:
+
+::
+
+    $ cabal new-install --lib Cabal --package-env myenv
+
+If you wish to create a named environment file in the current directory where
+the name does not contain an extension, you must reference it as ``./myenv``.
+
+You can learn more about how to use these environments in `this section of the
+GHC manual <https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/packages.html#package-environments>`_.
 
 cabal new-clean
 ---------------
@@ -515,16 +568,6 @@ byte) that must be satisfied for it to function correctly in the larger new-buil
 ``autogen-modules`` is able to replace uses of the hooks to add generated modules, along with
 the custom publishing of Haddock documentation to Hackage.
 
-Unsupported commands
---------------------
-
-The following commands are not currently supported:
-
-``cabal new-install`` (libraries and local executables)
-    (:issue:`3737` and :issue:`4558`)
-    Workaround: no good workaround at the moment. (But note that you no
-    longer need to install libraries before building!)
-
 Configuring builds with cabal.project
 =====================================
 

cabal-install/Distribution/Client/CmdBench.hs

@@ -100,6 +100,7 @@ benchAction (configFlags, configExFlags, installFlags, haddockFlags)
                          selectComponentTarget
                          TargetProblemCommon
                          elaboratedPlan
+                         Nothing
                          targetSelectors
 
             let elaboratedPlan' = pruneInstallPlanToTargets

cabal-install/Distribution/Client/CmdBuild.hs

@@ -91,6 +91,7 @@ buildAction (configFlags, configExFlags, installFlags, haddockFlags)
                          selectComponentTarget
                          TargetProblemCommon
                          elaboratedPlan
+                         Nothing
                          targetSelectors
 
             let elaboratedPlan' = pruneInstallPlanToTargets

cabal-install/Distribution/Client/CmdErrorMessages.hs

@@ -197,6 +197,12 @@ renderTargetProblemCommon verb (TargetNotInProject pkgname) =
  ++ "in this project (either directly or indirectly). If you want to add it "
  ++ "to the project then edit the cabal.project file."
 
+renderTargetProblemCommon verb (TargetAvailableInIndex pkgname) =
+    "Cannot " ++ verb ++ " the package " ++ display pkgname ++ ", it is not "
+ ++ "in this project (either directly or indirectly), but it is in the current "
+ ++ "package index. If you want to add it to the project then edit the "
+ ++ "cabal.project file."
+
 renderTargetProblemCommon verb (TargetComponentNotProjectLocal pkgid cname _) =
     "Cannot " ++ verb ++ " the " ++ showComponentName cname ++ " because the "
  ++ "package " ++ display pkgid ++ " is not local to the project, and cabal "

cabal-install/Distribution/Client/CmdHaddock.hs

@@ -94,6 +94,7 @@ haddockAction (configFlags, configExFlags, installFlags, haddockFlags)
                          selectComponentTarget
                          TargetProblemCommon
                          elaboratedPlan
+                         Nothing
                          targetSelectors
 
             let elaboratedPlan' = pruneInstallPlanToTargets