One-component configure, fixes #2802.

Described in: ghc-proposals/ghc-proposals#4

./Setup configure now takes an argument to specify a specific
component name that should solely be configured.

Most of the gyrations in Configure are all about making it so that
we can feed in internal dependencies via --dependency.

I dropped the package name match sanity check to handle convenience
library package name munging.  Consider an internal library named
'q' in package 'p'.  When we install it to the package database,
we munged the package name into 'z-p-z-q', so that it doesn't
conflict with the actual package named 'q'.  Now consider when
we feed it in with --dependency q=p-0.1-hash-q.  Previously,
Cabal checked that the 'q' in --dependency matched the package
name in the database... which it doesn't. So I dropped the check.

I also had to make register/copy unconditionally install internal
libraries; otherwise you can't refer to them from later builds.

Also a miscellaneous refactor: convenience libraries are printed with a
"header" stanza now (not really a stanza header).

Signed-off-by: Edward Z. Yang <[email protected]>

Author: ezyang

Cabal/Cabal.cabal

@@ -108,6 +108,17 @@ extra-source-files:
   tests/PackageTests/Configure/include/HsZlibConfig.h.in
   tests/PackageTests/Configure/zlib.buildinfo.in
   tests/PackageTests/Configure/zlib.cabal
+  tests/PackageTests/ConfigureComponent/Exe/Bad.hs
+  tests/PackageTests/ConfigureComponent/Exe/Exe.cabal
+  tests/PackageTests/ConfigureComponent/Exe/Good.hs
+  tests/PackageTests/ConfigureComponent/SubLib/Lib.cabal
+  tests/PackageTests/ConfigureComponent/SubLib/Lib.hs
+  tests/PackageTests/ConfigureComponent/SubLib/exe/Exe.hs
+  tests/PackageTests/ConfigureComponent/Test/Lib.hs
+  tests/PackageTests/ConfigureComponent/Test/Test.cabal
+  tests/PackageTests/ConfigureComponent/Test/testlib/TestLib.hs
+  tests/PackageTests/ConfigureComponent/Test/testlib/testlib.cabal
+  tests/PackageTests/ConfigureComponent/Test/tests/Test.hs
   tests/PackageTests/CopyAssumeDepsUpToDate/CopyAssumeDepsUpToDate.cabal
   tests/PackageTests/CopyAssumeDepsUpToDate/Main.hs
   tests/PackageTests/CopyAssumeDepsUpToDate/P.hs

Cabal/Distribution/PackageDescription/Configuration.hs

@@ -421,11 +421,14 @@ overallDependencies enabled (TargetSet targets) = mconcat depss
   where
     (depss, _) = unzip $ filter (removeDisabledSections . snd) targets
     removeDisabledSections :: PDTagged -> Bool
-    removeDisabledSections (Lib l)     = componentEnabled enabled (CLib l)
-    removeDisabledSections (SubLib _ l) = componentEnabled enabled (CLib l)
-    removeDisabledSections (Exe _ e)   = componentEnabled enabled (CExe e)
-    removeDisabledSections (Test _ t)  = componentEnabled enabled (CTest t)
-    removeDisabledSections (Bench _ b) = componentEnabled enabled (CBench b)
+    -- UGH. The embedded componentName in the 'Component's here is
+    -- BLANK.  I don't know whose fault this is but I'll use the tag
+    -- instead. -- ezyang
+    removeDisabledSections (Lib _)     = componentNameEnabled enabled CLibName
+    removeDisabledSections (SubLib t _) = componentNameEnabled enabled (CSubLibName t)
+    removeDisabledSections (Exe t _)   = componentNameEnabled enabled (CExeName t)
+    removeDisabledSections (Test t _)  = componentNameEnabled enabled (CTestName t)
+    removeDisabledSections (Bench t _) = componentNameEnabled enabled (CBenchName t)
     removeDisabledSections PDNull      = True
 
 -- Apply extra constraints to a dependency map.

Cabal/Distribution/Simple.hs

@@ -579,7 +579,6 @@ defaultUserHooks = autoconfUserHooks {
     -- https://github.com/haskell/cabal/issues/158
     where oldCompatPostConf args flags pkg_descr lbi
               = do let verbosity = fromFlag (configVerbosity flags)
-                   noExtraFlags args
                    confExists <- doesFileExist "configure"
                    when confExists $
                        runConfigureScript verbosity
@@ -610,7 +609,6 @@ autoconfUserHooks
     where defaultPostConf :: Args -> ConfigFlags -> PackageDescription -> LocalBuildInfo -> IO ()
           defaultPostConf args flags pkg_descr lbi
               = do let verbosity = fromFlag (configVerbosity flags)
-                   noExtraFlags args
                    confExists <- doesFileExist "configure"
                    if confExists
                      then runConfigureScript verbosity

Cabal/Distribution/Simple/BuildTarget.hs

@@ -12,6 +12,7 @@
 module Distribution.Simple.BuildTarget (
     -- * Main interface
     readTargetInfos,
+    readBuildTargets, -- in case you don't have LocalBuildInfo
 
     -- * Build targets
     BuildTarget(..),
@@ -998,3 +999,7 @@ checkBuildTargets verbosity pkg_descr lbi targets = do
     formatReason cn DisabledAllBenchmarks =
         "Cannot process the " ++ cn ++ " because benchmarks are not "
      ++ "enabled. Re-run configure with the flag --enable-benchmarks"
+    formatReason cn (DisabledAllButOne cn') =
+        "Cannot process the " ++ cn ++ " because this package was "
+     ++ "configured only to build " ++ cn' ++ ". Re-run configure "
+     ++ "with the argument " ++ cn

Cabal/Distribution/Simple/Configure.hs

@@ -1138,20 +1138,17 @@ installLib    :: Verbosity
               -> Library
               -> ComponentLocalBuildInfo
               -> IO ()
-installLib verbosity lbi targetDir dynlibTargetDir _builtDir pkg lib clbi = do
+installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
   -- copy .hi files over:
-  whenRegistered $ do
-    whenVanilla $ copyModuleFiles "hi"
-    whenProf    $ copyModuleFiles "p_hi"
-    whenShared  $ copyModuleFiles "dyn_hi"
+  whenVanilla $ copyModuleFiles "hi"
+  whenProf    $ copyModuleFiles "p_hi"
+  whenShared  $ copyModuleFiles "dyn_hi"
 
   -- copy the built library files over:
-  whenRegistered $ do
-    whenVanilla $ installOrdinary builtDir targetDir       vanillaLibName
-    whenProf    $ installOrdinary builtDir targetDir       profileLibName
-    whenGHCi    $ installOrdinary builtDir targetDir       ghciLibName
-  whenRegisteredOrDynExecutable $ do
-    whenShared  $ installShared   builtDir dynlibTargetDir sharedLibName
+  whenVanilla $ installOrdinary builtDir targetDir       vanillaLibName
+  whenProf    $ installOrdinary builtDir targetDir       profileLibName
+  whenGHCi    $ installOrdinary builtDir targetDir       ghciLibName
+  whenShared  $ installShared   builtDir dynlibTargetDir sharedLibName
 
   where
     builtDir = componentBuildDir lbi clbi
@@ -1189,17 +1186,6 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir pkg lib clbi = do
     whenGHCi    = when (hasLib && withGHCiLib    lbi)
     whenShared  = when (hasLib && withSharedLib  lbi)
 
-    -- Some files (e.g. interface files) are completely unnecessary when
-    -- we are not actually going to register the library.  A library is
-    -- not registered if there is no "public library", e.g. in the case
-    -- that we have an internal library and executables, but no public
-    -- library.
-    whenRegistered = when (hasPublicLib pkg)
-
-    -- However, we must always install dynamic libraries when linking
-    -- dynamic executables, because we'll try to load them!
-    whenRegisteredOrDynExecutable = when (hasPublicLib pkg || (hasExes pkg && withDynExe lbi))
-
 -- -----------------------------------------------------------------------------
 -- Registering
 

Cabal/Distribution/Simple/GHC.hs

@@ -25,6 +25,7 @@ module Distribution.Simple.InstallDirs (
         InstallDirs(..),
         InstallDirTemplates,
         defaultInstallDirs,
+        defaultInstallDirs',
         combineInstallDirs,
         absoluteInstallDirs,
         CopyDest(..),
@@ -156,7 +157,17 @@ type InstallDirTemplates = InstallDirs PathTemplate
 -- Default installation directories
 
 defaultInstallDirs :: CompilerFlavor -> Bool -> Bool -> IO InstallDirTemplates
-defaultInstallDirs comp userInstall _hasLibs = do
+defaultInstallDirs = defaultInstallDirs' False
+
+defaultInstallDirs' :: Bool {- use external internal deps -}
+                    -> CompilerFlavor -> Bool -> Bool -> IO InstallDirTemplates
+defaultInstallDirs' True comp userInstall hasLibs = do
+  dflt <- defaultInstallDirs' False comp userInstall hasLibs
+  -- Be a bit more hermetic about per-component installs
+  return dflt { datasubdir = toPathTemplate $ "$abi" </> "$libname",
+                docdir     = toPathTemplate $ "$datadir" </> "doc" </> "$abi" </> "$libname"
+              }
+defaultInstallDirs' False comp userInstall _hasLibs = do
   installPrefix <-
       if userInstall
       then getAppUserDataDirectory "cabal"

Cabal/Distribution/Simple/InstallDirs.hs

@@ -88,12 +88,13 @@ import qualified Data.ByteString.Lazy.Char8 as BS.Char8
 register :: PackageDescription -> LocalBuildInfo
          -> RegisterFlags -- ^Install in the user's database?; verbose
          -> IO ()
-register pkg_descr lbi flags = when (hasPublicLib pkg_descr) doRegister
+register pkg_descr lbi flags =
+   -- Duncan originally asked for us to not register/install files
+   -- when there was no public library.  But with per-component
+   -- configure, we legitimately need to install internal libraries
+   -- so that we can get them.  So just unconditionally install.
+   doRegister
  where
-  -- We do NOT register libraries outside of the inplace database
-  -- if there is no public library, since no one else can use it
-  -- usefully (they're not public.)  If we start supporting scoped
-  -- packages, we'll have to relax this.
   doRegister = do
     targets <- readTargetInfos verbosity pkg_descr lbi (regArgs flags)
 

Cabal/Distribution/Simple/Register.hs

@@ -391,6 +391,7 @@ data ConfigFlags = ConfigFlags {
                                               -- frameworks (OS X only)
     configExtraIncludeDirs :: [FilePath],   -- ^ path to search for header files
     configIPID          :: Flag String, -- ^ explicit IPID to be used
+    configCID           :: Flag ComponentId, -- ^ explicit CID to be used
 
     configDistPref :: Flag FilePath, -- ^"dist" prefix
     configCabalFilePath :: Flag FilePath, -- ^ Cabal file to use
@@ -677,6 +678,11 @@ configureOptions showOrParseArgs =
          configIPID (\v flags -> flags {configIPID = v})
          (reqArgFlag "IPID")
 
+      ,option "" ["cid"]
+         "Installed component ID to compile this component as"
+         (fmap display . configCID) (\v flags -> flags {configCID = fmap ComponentId v})
+         (reqArgFlag "CID")
+
       ,option "" ["extra-lib-dirs"]
          "A list of directories to search for external libraries"
          configExtraLibDirs (\v flags -> flags {configExtraLibDirs = v})

Cabal/Distribution/Simple/Setup.hs

@@ -164,7 +164,7 @@ emptyUserHooks
       readDesc  = return Nothing,
       hookedPreProcessors = [],
       hookedPrograms      = [],
-      preConf   = rn,
+      preConf   = rn',
       confHook  = (\_ _ -> return (error "No local build info generated during configure. Over-ride empty configure hook.")),
       postConf  = ru,
       preBuild  = rn',

Cabal/Distribution/Simple/UserHooks.hs

@@ -15,6 +15,7 @@ module Distribution.Types.ComponentEnabledSpec (
 
 import Prelude ()
 import Distribution.Compat.Prelude
+import Distribution.Text
 
 import Distribution.Types.Component -- TODO: maybe remove me?
 import Distribution.Types.ComponentName
@@ -50,10 +51,9 @@ import Distribution.Types.ComponentName
 --
 -- @since 2.0.0.0
 data ComponentEnabledSpec
-    = ComponentEnabledSpec {
-        testsEnabled :: Bool,
-        benchmarksEnabled :: Bool
-   }
+    = ComponentEnabledSpec { testsEnabled :: Bool,
+                             benchmarksEnabled :: Bool }
+    | OneComponentEnabledSpec ComponentName
   deriving (Generic, Read, Show)
 instance Binary ComponentEnabledSpec
 
@@ -91,15 +91,21 @@ componentDisabledReason enabled comp
 -- @since 2.0.0.0
 componentNameDisabledReason :: ComponentEnabledSpec -> ComponentName
                             -> Maybe ComponentDisabledReason
-componentNameDisabledReason enabled (CTestName _)
-    | not (testsEnabled enabled) = Just DisabledAllTests
-componentNameDisabledReason enabled (CBenchName _)
-    | not (benchmarksEnabled enabled) = Just DisabledAllBenchmarks
-componentNameDisabledReason _ _ = Nothing
+componentNameDisabledReason
+    ComponentEnabledSpec{ testsEnabled      = False } (CTestName _)
+    = Just DisabledAllTests
+componentNameDisabledReason
+    ComponentEnabledSpec{ benchmarksEnabled = False } (CBenchName _)
+    = Just DisabledAllBenchmarks
+componentNameDisabledReason ComponentEnabledSpec{} _ = Nothing
+componentNameDisabledReason (OneComponentEnabledSpec cname) c
+    | c == cname = Nothing
+    | otherwise = Just (DisabledAllButOne (display cname))
 
 -- | A reason explaining why a component is disabled.
 --
 -- @since 2.0.0.0
 data ComponentDisabledReason = DisabledComponent
                              | DisabledAllTests
                              | DisabledAllBenchmarks
+                             | DisabledAllButOne String

Cabal/Distribution/Types/ComponentEnabledSpec.hs

@@ -66,6 +66,10 @@
 	internal use.
 	* Macros in 'cabal_macros.h' are now ifndef'd, so that they
 	don't cause an error if the macro is already defined. (#3041)
+	* './Setup configure' now accepts a single argument specifying
+	  the component to be configured.  The semantics of this mode
+	  of operation are described in
+	  <https://github.com/ghc-proposals/ghc-proposals/pull/4>
 
 1.24.0.0 Ryan Thomas <[email protected]> March 2016
 	* Support GHC 8.

Cabal/changelog

@@ -410,6 +410,35 @@ is passed the `--with-hc-pkg`, `--prefix`, `--bindir`, `--libdir`,
 value of the `--with-compiler` option is passed in a `--with-hc` option
 and all options specified with `--configure-option=` are passed on.
 
+In Cabal 2.0, support for a single positional argument was added to `setup configure`
+This makes Cabal configure a the specific component to be
+configured.  Specified names can be qualified with `lib:` or
+`exe:` in case just a name is ambiguous (as would be the case
+for a package named `p` which has a library and an executable
+named `p`.)  This has the following effects:
+
+* Subsequent invocations of `build`, `register`, etc. operate only
+  on the configured component.
+
+* Cabal requires all "internal" dependencies (e.g., an executable
+  depending on a library defined in the same package) must be
+  found in the set of databases via `--package-db` (and related flags):
+  these dependencies are assumed to be up-to-date.  A dependency can
+  be explicitly specified using `--dependency` simply by giving
+  the name of the internal library; e.g., the dependency for an
+  internal library named `foo` is given as `--dependency=pkg-internal=pkg-1.0-internal-abcd`.
+
+* Only the dependencies needed for the requested component are
+  required.  Similarly, when `--exact-configuration` is specified,
+  it's only necessary to specify `--dependency` for the component.
+  (As mentioned previously, you *must* specify internal dependencies
+  as well.)
+
+* Internal `build-tools` dependencies are expected to be in the `PATH`
+  upon subsequent invocations of `setup`.
+
+Full details can be found in the [Componentized Cabal proposal](https://github.com/ezyang/ghc-proposals/blob/master/proposals/0000-componentized-cabal.rst).
+
 ### Programs used for building ###
 
 The following options govern the programs used to process the source
@@ -753,6 +782,19 @@ be controlled with the following command line options.
 
     To reset the stack, use `--package-db=clear`.
 
+`--ipid=`_ipid_
+:   Specifies the _installed package identifier_ of the package to be
+    built; this identifier is passed on to GHC and serves as the basis
+    for linker symbols and the `id` field in a `ghc-pkg` registration.
+    When a package has multiple components, the actual component
+    identifiers are derived off of this identifier (e.g., an
+    internal library `foo` from package `p-0.1-abcd` will get the
+    identifier `p-0.1-abcd-foo`.
+
+`--cid=`_cid_
+:   Specifies the _component identifier_ of the component being built;
+    this is only valid if you are configuring a single component.
+
 `--default-user-config=` _file_
 :   Allows a "default" `cabal.config` freeze file to be passed in
     manually. This file will only be used if one does not exist in the
@@ -954,6 +996,18 @@ be controlled with the following command line options.
     for libraries it is also saved in the package registration
     information and used when compiling modules that use the library.
 
+`--dependency`[=_pkgname_=_ipid_]
+:   Specify that a particular dependency should used for a particular
+    package name. In particular, it declares that any reference to
+    _pkgname_ in a `build-depends` should be resolved to _ipid_.
+
+`--exact-configuration`
+:   This changes Cabal to require every dependency be explicitly
+    specified using `--dependency`, rather than use Cabal's
+    (very simple) dependency solver.  This is useful for programmatic
+    use of Cabal's API, where you want to error if you didn't
+    specify enough `--dependency` flags.
+
 `--allow-newer`[=_pkgs_], `--allow-older`[=_pkgs_]
 :   Selectively relax upper or lower bounds in dependencies without
     editing the package description respectively.

Cabal/doc/installing-packages.markdown

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, Haskell!"

Cabal/tests/PackageTests/ConfigureComponent/Exe/Bad.hs

@@ -0,0 +1,18 @@
+name:                Exe
+version:             0.1.0.0
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          [email protected]
+build-type:          Simple
+cabal-version:       >=1.10
+
+executable goodexe
+  main-is:             Good.hs
+  build-depends:       base
+  default-language:    Haskell2010
+
+-- We deliberately don't configure badexe, so that we can build ONLY goodexe
+executable badexe
+  main-is:             Bad.hs
+  build-depends:       totally-impossible-dependency-to-fill == 10000.25.6
+  default-language:    Haskell2010

Cabal/tests/PackageTests/ConfigureComponent/Exe/Exe.cabal

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "OK"

Cabal/tests/PackageTests/ConfigureComponent/Exe/Good.hs

@@ -0,0 +1,18 @@
+name:                Lib
+version:             0.1.0.0
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          [email protected]
+build-type:          Simple
+cabal-version:       >=1.10
+
+library sublib
+  build-depends:       base
+  exposed-modules:     Lib
+  default-language:    Haskell2010
+
+executable exe
+  main-is:             Exe.hs
+  build-depends:       base, sublib
+  hs-source-dirs:      exe
+  default-language:    Haskell2010

Cabal/tests/PackageTests/ConfigureComponent/SubLib/Lib.cabal

@@ -0,0 +1,2 @@
+module Lib where
+lib = "OK"

Cabal/tests/PackageTests/ConfigureComponent/SubLib/Lib.hs

@@ -0,0 +1,2 @@
+import Lib
+main = putStrLn lib

Cabal/tests/PackageTests/ConfigureComponent/SubLib/exe/Exe.hs

@@ -0,0 +1,2 @@
+module Lib where
+lib = "OK"