Merge branch 'no-cabal-hgettext'

https://github.com/fpco/stackage/issues/746

6 files changed, 534 insertions, 66 deletions

diff --git a/.travis.yml b/.travis.yml
index aa8be2f..8b3e518 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,58 +1,79 @@
+# This file has been generated -- see https://github.com/hvr/multi-ghc-travis
+language: c
 sudo: false
 
-env:
-# TODO
-# # Fedora 22:
-#  - CABALVER=1.18 GHCVER=7.8.4
-# 7.10.2 is not in the magic whitelist at https://github.com/travis-ci/apt-package-whitelist/blob/master/ubuntu-precise
- - CABALVER=1.22 GHCVER=7.10.1
- - CABALVER=head GHCVER=head
+cache:
+  directories:
+    - $HOME/.cabsnap
+    - $HOME/.cabal/packages
+
+before_cache:
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/build-reports.log
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/00-index.tar
 
 matrix:
-  allow_failures:
-   - env: CABALVER=head GHCVER=head
-
-addons:
-  apt:
-    sources:
-    # https://github.com/hvr/multi-ghc-travis
-    - hvr-ghc
-    packages:
-    - libpcap-dev
-    - libgtk-3-dev
-    - libcairo2-dev
-    # GAH: I guess env does not have any effect here
-    - cabal-install-1.18
-    - cabal-install-1.22
-    - cabal-install-head
-    - ghc-7.8.4
-    - ghc-7.10.1
-    - ghc-head
-    # /GAH
-    - happy-1.19.4
-    - alex-3.1.3
+  include:
+    - env: CABALVER=1.18 GHCVER=7.8.4
+      compiler: ": #GHC 7.8.4"
+      addons: {apt: {packages: [cabal-install-1.18,ghc-7.8.4,libpcap-dev,libgtk-3-dev,libcairo2-dev,happy-1.19.4,alex-3.1.3], sources: [hvr-ghc]}}
+    - env: CABALVER=1.22 GHCVER=7.10.1
+      compiler: ": #GHC 7.10.1"
+      addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.1,libpcap-dev,libgtk-3-dev,libcairo2-dev,happy-1.19.4,alex-3.1.3], sources: [hvr-ghc]}}
+
+before_install:
+ - unset CC
+ - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:/opt/happy/1.19.4/bin:/opt/alex/3.1.3/bin:$PATH
 
 install:
-# Is it just not installing those packages?
- - dpkg -l
- - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:/opt/alex/3.1.3/bin:/opt/happy/1.19.4/bin:$PATH
  - cabal --version
  - echo "$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]"
- - ghc-pkg list Cabal
- - travis_retry cabal update
-# TODO: shouldn't gtk3 et al build-depend on this? Should we do so?
- - cabal install gtk2hs-buildtools
- - cabal install --only-dependencies --enable-tests --enable-benchmarks
+ - if [ -f $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz ];
+   then
+     zcat $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz >
+          $HOME/.cabal/packages/hackage.haskell.org/00-index.tar;
+   fi
+ - travis_retry cabal update -v
+ - sed -i 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config
+ - cabal install --only-dependencies --enable-tests --enable-benchmarks --flags='WithGtk2HsBuildTools' --dry -v > installplan.txt
+ - sed -i -e '1,/^Resolving /d' installplan.txt; cat installplan.txt
+
+# check whether current requested install-plan matches cached package-db snapshot
+ - if diff -u installplan.txt $HOME/.cabsnap/installplan.txt;
+   then
+     echo "cabal build-cache HIT";
+     rm -rfv .ghc;
+     cp -a $HOME/.cabsnap/ghc $HOME/.ghc;
+     cp -a $HOME/.cabsnap/lib $HOME/.cabsnap/share $HOME/.cabsnap/bin $HOME/.cabal/;
+   else
+     echo "cabal build-cache MISS";
+     rm -rf $HOME/.cabsnap;
+     mkdir -p $HOME/.ghc $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin;
+     travis_retry cabal install --only-dependencies --enable-tests --enable-benchmarks --flags='WithGtk2HsBuildTools';
+   fi
+ 
+# snapshot package-db on cache miss
+ - if [ ! -d $HOME/.cabsnap ];
+   then
+      echo "snapshotting package-db to build-cache";
+      mkdir $HOME/.cabsnap;
+      cp -a $HOME/.ghc $HOME/.cabsnap/ghc;
+      cp -a $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin installplan.txt $HOME/.cabsnap/;
+   fi
 
+# Here starts the actual work to be performed for the package under test;
+# any command which exits with a non-zero exit code causes the build to fail.
 script:
  - if [ -f configure.ac ]; then autoreconf -i; fi
- - cabal configure --enable-tests --enable-benchmarks -v2
- - cabal build
- - cabal test
+ - cabal configure --enable-tests --enable-benchmarks -v2  # -v2 provides useful information for debugging
+ - cabal build   # this builds all libraries and executables (including tests/benchmarks)
+ - ./dist/setup/setup test
  - cabal check
- - cabal sdist
+ - cabal sdist   # tests that a source-distribution can be generated
+
 # Check that the resulting source distribution can be built & installed.
 # If there are no other `.tar.gz` files in `dist`, this can be even simpler:
 # `cabal install --force-reinstalls dist/*-*.tar.gz`
  - SRC_TGZ=$(cabal info . | awk '{print $2;exit}').tar.gz &&
    (cd dist && cabal install --force-reinstalls "$SRC_TGZ")
+
+# EOF
diff --git a/GetText.hs b/GetText.hs
new file mode 100644
index 0000000..1c27146
--- /dev/null
+++ b/GetText.hs
@@ -0,0 +1,220 @@
+-- | This library extends the Distribution with internationalization support.
+--
+-- It performs two functions:
+--
+-- * compiles and installs PO files to the specified directory
+--
+-- * tells the application where files were installed to make it able
+-- to bind them to the code
+--
+-- Each PO file will be placed to the
+-- @{datadir}\/locale\/{loc}\/LC_MESSAGES\/{domain}.mo@ where:
+--
+--  [@datadir@] Usually @prefix/share@ but could be different, depends
+--  on system.
+--
+--  [@loc@] Locale name (language code, two characters). This module
+--  supposes, that each PO file has a base name set to the proper
+--  locale, e.g. @de.po@ is the German translation of the program, so
+--  this file will be placed under @{datadir}\/locale\/de@ directory
+--
+--  [@domain@] Program domain. A unique identifier of single
+--  translational unit (program). By default domain will be set to the
+--  package name, but its name could be configured in the @.cabal@ file.
+--
+-- The module defines following @.cabal@ fields:
+--
+--  [@x-gettext-domain-name@] Name of the domain. One ofmore
+--  alphanumeric characters separated by hyphens or underlines. When
+--  not set, package name will be used.
+--
+--  [@x-gettext-po-files@] List of files with translations. Could be
+--  used a limited form of wildcards, e.g.: @x-gettext-po-files:
+--  po/*.po@
+--
+--  [@x-gettext-domain-def@] Name of the macro, in which domain name
+--  will be passed to the program. Default value is
+--  @__MESSAGE_CATALOG_DOMAIN__@
+--
+--  [@x-gettext-msg-cat-def@] Name of the macro, in which path to the
+--  message catalog will be passed to the program. Default value is
+--  @__MESSAGE_CATALOG_DIR__@
+--
+-- The last two parameters are used to send configuration data to the
+-- code during its compilation. The most common usage example is:
+--
+--
+-- > ...
+-- > prepareI18N = do
+-- >    setLocale LC_ALL (Just "") 
+-- >    bindTextDomain __MESSAGE_CATALOG_DOMAIN__ (Just __MESSAGE_CATALOG_DIR__)
+-- >    textDomain __MESSAGE_CATALOG_DOMAIN__
+-- >
+-- > main = do
+-- >    prepareI18N
+-- >    ...
+-- >
+-- > ...
+--
+--
+-- /NOTE:/ files, passed in the @x-gettext-po-files@ are not
+-- automatically added to the source distribution, so they should be
+-- also added to the @extra-source-files@ parameter, along with
+-- translation template file (usually @message.pot@)
+--
+-- /WARNING:/ sometimes, when only configuration targets changes, code
+-- will not recompile, thus you should execute @cabal clean@ to
+-- cleanup the build and restart it again from the configuration. This
+-- is temporary bug, it will be fixed in next releases.
+--
+-- /TODO:/ this is lifted verbatim (modulo other /TODO/s) from hgettext's
+-- Distribution.Simple.I18N.GetText partly to expose individual hooks and
+-- partly to avoid the /cabal configure/-time dependency. For the latter,
+-- see https://github.com/fpco/stackage/issues/746
+-- 
+
+module GetText 
+    (
+    -- | /TODO:/ upstream exporting the individual hooks?
+     installPOFiles,
+
+    -- | /TODO:/ upstream generating GetText_foo.hs rather than exporting these?
+     getDomainNameDefault,
+     getPackageName,
+     targetDataDir,
+
+     installGetTextHooks,
+     gettextDefaultMain
+    ) where
+
+import Distribution.Simple
+import Distribution.Simple.Setup as S
+import Distribution.Simple.LocalBuildInfo
+import Distribution.PackageDescription
+import Distribution.Simple.Configure
+import Distribution.Simple.InstallDirs as I
+import Distribution.Simple.Utils
+
+import Language.Haskell.Extension
+
+import Control.Monad
+import Control.Arrow (second)
+import Data.Maybe (listToMaybe, maybeToList, fromMaybe)
+import Data.List (unfoldr,nub,null)
+import System.FilePath
+import System.Directory
+import System.Process
+
+-- | Default main function, same as
+-- 
+-- > defaultMainWithHooks $ installGetTextHooks simpleUserHooks
+-- 
+gettextDefaultMain :: IO ()
+gettextDefaultMain = defaultMainWithHooks $ installGetTextHooks simpleUserHooks
+
+-- | Installs hooks, used by GetText module to install
+-- PO files to the system. Previous won't be disabled
+--
+installGetTextHooks :: UserHooks -- ^ initial user hooks
+                    -> UserHooks -- ^ patched user hooks
+installGetTextHooks uh = uh{
+                           confHook = \a b -> 
+                                      (confHook uh) a b >>= 
+                                      return . updateLocalBuildInfo,
+
+                           postInst = \a b c d -> 
+                                      (postInst uh) a b c d >> 
+                                      installPOFiles a b c d
+                         }
+
+
+updateLocalBuildInfo :: LocalBuildInfo -> LocalBuildInfo
+updateLocalBuildInfo l = 
+    let sMap = getCustomFields l
+        [domDef, catDef] = map ($ sMap) [getDomainDefine, getMsgCatalogDefine]
+        dom = getDomainNameDefault sMap (getPackageName l)
+        tar = targetDataDir l
+        [catMS, domMS] = map (uncurry formatMacro) [(domDef, dom), (catDef, tar)]
+    in (appendCPPOptions [domMS,catMS] . appendExtension [EnableExtension CPP]) l
+
+installPOFiles :: Args -> InstallFlags -> PackageDescription -> LocalBuildInfo -> IO ()
+installPOFiles _ _ _ l = 
+    let sMap = getCustomFields l
+        destDir = targetDataDir l
+        dom = getDomainNameDefault sMap (getPackageName l)
+        installFile file = do
+          let fname = takeFileName file
+          let bname = takeBaseName fname
+          let targetDir = destDir </> bname </> "LC_MESSAGES"
+          -- ensure we have directory destDir/{loc}/LC_MESSAGES
+          createDirectoryIfMissing True targetDir
+          system $ "msgfmt --output-file=" ++ 
+                     (targetDir </> dom <.> "mo") ++ 
+                     " " ++ file
+    in do
+      filelist <- getPoFilesDefault sMap
+      -- copy all whose name is in the form of dir/{loc}.po to the
+      -- destDir/{loc}/LC_MESSAGES/dom.mo
+      -- with the 'msgfmt' tool
+      mapM_ installFile filelist      
+
+forBuildInfo :: LocalBuildInfo -> (BuildInfo -> BuildInfo) -> LocalBuildInfo
+forBuildInfo l f = 
+    let a = l{localPkgDescr = updPkgDescr (localPkgDescr l)}
+        updPkgDescr x = x{library = updLibrary (library x), 
+                          executables = updExecs (executables x)}
+        updLibrary Nothing = Nothing
+        updLibrary (Just x) = Just $ x{libBuildInfo = f (libBuildInfo x)}
+        updExecs x = map updExec x
+        updExec x = x{buildInfo = f (buildInfo x)}
+    in a
+
+appendExtension :: [Extension] -> LocalBuildInfo -> LocalBuildInfo
+appendExtension exts l = 
+    forBuildInfo l updBuildInfo
+    where updBuildInfo x = x{defaultExtensions = updExts (defaultExtensions x)}
+          updExts s = nub (s ++ exts)
+
+appendCPPOptions :: [String] -> LocalBuildInfo -> LocalBuildInfo
+appendCPPOptions opts l = 
+    forBuildInfo l updBuildInfo
+    where updBuildInfo x = x{cppOptions = updOpts (cppOptions x)}
+          updOpts s = nub (s ++ opts)
+
+formatMacro name value = "-D" ++ name ++ "=" ++ (show value)
+
+targetDataDir :: LocalBuildInfo -> FilePath
+targetDataDir l = 
+    let dirTmpls = installDirTemplates l
+        prefix' = prefix dirTmpls
+        data' = datadir dirTmpls
+        dataEx = I.fromPathTemplate $ I.substPathTemplate [(PrefixVar, prefix')] data'
+    in dataEx ++ "/locale"
+
+getPackageName :: LocalBuildInfo -> String
+getPackageName = fromPackageName . packageName . localPkgDescr
+    where fromPackageName (PackageName s) = s
+
+getCustomFields :: LocalBuildInfo -> [(String, String)]
+getCustomFields = customFieldsPD . localPkgDescr
+
+findInParametersDefault :: [(String, String)] -> String -> String -> String
+findInParametersDefault al name def = (fromMaybe def . lookup name) al
+
+getDomainNameDefault :: [(String, String)] -> String -> String
+getDomainNameDefault al d = findInParametersDefault al "x-gettext-domain-name" d
+
+getDomainDefine :: [(String, String)] -> String
+getDomainDefine al = findInParametersDefault al "x-gettext-domain-def" "__MESSAGE_CATALOG_DOMAIN__"
+
+getMsgCatalogDefine :: [(String, String)] -> String
+getMsgCatalogDefine al = findInParametersDefault al "x-gettext-msg-cat-def" "__MESSAGE_CATALOG_DIR__"
+
+getPoFilesDefault :: [(String, String)] -> IO [String]
+getPoFilesDefault al = toFileList $ findInParametersDefault al "x-gettext-po-files" ""
+    where toFileList "" = return []
+          toFileList x = liftM concat $ mapM matchFileGlob $ split' x
+          -- from Blow your mind (HaskellWiki)
+          -- splits string by newline, space and comma
+          split' x = concatMap lines $ concatMap words $ unfoldr (\b -> fmap (const . (second $ drop 1) . break (==',') $ b) . listToMaybe $ b) x
+
diff --git a/Makefile b/Makefile
index 12ba32a..459b2f2 100644
--- a/Makefile
+++ b/Makefile
@@ -123,3 +123,6 @@ maintainer-make-release: bustle.cabal dist/build/autogen/version.txt
 	git tag -s -m 'Bustle '`cat dist/build/autogen/version.txt` \
 		bustle-`cat dist/build/autogen/version.txt`
 	make maintainer-binary-tarball
+
+.travis.yml: bustle.cabal make_travis_yml.hs
+	./make_travis_yml.hs $< libpcap-dev libgtk-3-dev libcairo2-dev happy-1.19.4 alex-3.1.3 > $@
diff --git a/Setup.hs b/Setup.hs
index 9ab758c..d067f7e 100644
--- a/Setup.hs
+++ b/Setup.hs
@@ -1,11 +1,9 @@
 {-# OPTIONS_GHC -Wall #-}
-import Data.Maybe (fromMaybe)
 import System.FilePath ( (</>), (<.>) )
 
 import Distribution.PackageDescription
 import Distribution.Simple
 import Distribution.Simple.BuildPaths ( autogenModulesDir )
-import Distribution.Simple.InstallDirs as I
 import Distribution.Simple.LocalBuildInfo
 import Distribution.Simple.Setup as S
 import Distribution.Simple.Utils
@@ -14,7 +12,7 @@ import Distribution.Text ( display )
 import Distribution.ModuleName (ModuleName)
 import qualified Distribution.ModuleName as ModuleName
 
-import qualified Distribution.Simple.I18N.GetText as GetText
+import qualified GetText as GetText
 
 main :: IO ()
 main = defaultMainWithHooks $ installBustleHooks simpleUserHooks
@@ -31,13 +29,13 @@ main = defaultMainWithHooks $ installBustleHooks simpleUserHooks
 installBustleHooks :: UserHooks
                    -> UserHooks
 installBustleHooks uh = uh
-  { postInst = postInst gtuh
+  { postInst = \a b c d -> do
+        postInst uh a b c d
+        GetText.installPOFiles a b c d
   , buildHook = \pkg lbi hooks flags -> do
         writeGetTextConstantsFile pkg lbi flags
         buildHook uh pkg lbi hooks flags
   }
-  where
-    gtuh = GetText.installGetTextHooks uh
 
 
 writeGetTextConstantsFile :: PackageDescription -> LocalBuildInfo -> BuildFlags -> IO ()
@@ -90,24 +88,7 @@ generateModule pkg lbi =
         "getMessageCatalogDir = catchIO (getEnv \"" ++ fixedPackageName pkg ++ "_localedir\") (\\_ -> return messageCatalogDir)\n"
 
     sMap = customFieldsPD (localPkgDescr lbi)
-    dom = getDomainNameDefault sMap (getPackageName lbi)
-    tar = targetDataDir lbi
+    dom = GetText.getDomainNameDefault sMap (GetText.getPackageName lbi)
+    tar = GetText.targetDataDir lbi
 
 -- Cargo-culted from hgettext
-findInParametersDefault :: [(String, String)] -> String -> String -> String
-findInParametersDefault al name def = (fromMaybe def . lookup name) al
-
-getPackageName :: LocalBuildInfo -> String
-getPackageName = fromPackageName . packageName . localPkgDescr
-    where fromPackageName (PackageName s) = s
-
-getDomainNameDefault :: [(String, String)] -> String -> String
-getDomainNameDefault al d = findInParametersDefault al "x-gettext-domain-name" d
-
-targetDataDir :: LocalBuildInfo -> FilePath
-targetDataDir l =
-    let dirTmpls = installDirTemplates l
-        prefix' = prefix dirTmpls
-        data' = datadir dirTmpls
-        dataEx = I.fromPathTemplate $ I.substPathTemplate [(PrefixVar, prefix')] data'
-    in dataEx ++ "/locale"
diff --git a/bustle.cabal b/bustle.cabal
index 05386d8..f9edb84 100644
--- a/bustle.cabal
+++ b/bustle.cabal
@@ -2,6 +2,7 @@ Name:           bustle
 Category:       Network, Desktop
 Version:        0.5.1
 Cabal-Version:  >= 1.18
+Tested-With:    GHC >= 7.8.4 && < 7.11
 Synopsis:       Draw sequence diagrams of D-Bus traffic
 Description:    Draw sequence diagrams of D-Bus traffic
 License:        OtherLicense
@@ -35,6 +36,10 @@ Extra-source-files:
                   , ldd-me-up.sh
                   , LICENSE.bundled-libraries
 
+                  -- inlined copy of the Cabal hooks from hgettext;
+                  -- see https://github.com/fpco/stackage/issues/746
+                  , GetText.hs
+
                   -- wow many translate
                   , po/*.po
                   , po/*.pot
@@ -67,6 +72,13 @@ Flag threaded
   Description:    Build with the multi-threaded runtime
   Default:        True
 
+Flag WithGtk2HsBuildTools
+  Description:    Build-depend on gtk2hs-buildtools. They aren't (currently)
+                  used to build Bustle itself but are needed to build
+                  dependencies like gtk3, which for whatever reason do not
+                  Build-Depend on the tools.
+  Default:        False
+
 Executable bustle
   Main-is:       Bustle.hs
   Other-modules: Bustle.Application.Monad
@@ -122,6 +134,9 @@ Executable bustle
                , text
                , time
 
+  if flag(WithGtk2HsBuildTools)
+    Build-Depends: gtk2hs-buildtools
+
 Executable test-monitor
   if flag(InteractiveTests)
     buildable: True
diff --git a/make_travis_yml.hs b/make_travis_yml.hs
new file mode 100755
index 0000000..551cbd5
--- /dev/null
+++ b/make_travis_yml.hs
@@ -0,0 +1,228 @@
+#!/usr/bin/env runghc
+
+-- NB: This code deliberately avoids relying on non-standard packages
+
+import Control.Monad
+import Data.Maybe
+import Data.List
+import System.Environment
+import System.Exit
+import System.IO
+
+import Distribution.PackageDescription.Parse (readPackageDescription)
+import Distribution.PackageDescription (packageDescription, testedWith)
+import Distribution.Compiler (CompilerFlavor(..))
+import Distribution.Version
+import Distribution.Text
+
+putStrLnErr :: String -> IO ()
+putStrLnErr m = hPutStrLn stderr ("*ERROR* " ++ m) >> exitFailure
+
+putStrLnWarn :: String -> IO ()
+putStrLnWarn m = hPutStrLn stderr ("*WARNING* " ++ m)
+
+putStrLnInfo :: String -> IO ()
+putStrLnInfo m = hPutStrLn stderr ("*INFO* " ++ m)
+
+main :: IO ()
+main = do
+    args <- getArgs
+    case args of
+        (cabfn:xpkgs) -> do genTravisFromCabalFile cabfn xpkgs
+        _ -> putStrLnErr (unlines $ [ "expected .cabal file as command-line argument"
+                                    , "Usage: make_travis_yml.hs <cabal-file> <extra-apt-packages...>"
+                                    , ""
+                                    , "Example: make_travis_yml.hs someProject.cabal alex-3.1.4 liblzma-dev > .travis.yml"
+                                    ])
+
+genTravisFromCabalFile :: FilePath -> [String] -> IO ()
+genTravisFromCabalFile fn xpkgs = do
+    gpd <- readPackageDescription maxBound fn
+
+    let compilers = testedWith $ packageDescription $ gpd
+
+    let unknownComps = nub [ c | (c,_) <- compilers, c /= GHC ]
+        ghcVerConstrs = [ vc | (GHC,vc) <- compilers ]
+        ghcVerConstrs' = simplifyVersionRange $ foldr unionVersionRanges noVersion ghcVerConstrs
+
+    when (null compilers) $ do
+        putStrLnErr "empty or missing 'tested-with:' definition in .cabal file"
+
+    unless (null unknownComps) $ do
+        putStrLnWarn $ "ignoring unsupported compilers mentioned in tested-with: " ++ show unknownComps
+
+    when (null ghcVerConstrs) $ do
+        putStrLnErr "'tested-with:' doesn't mention any 'GHC' version"
+
+    when (isNoVersion ghcVerConstrs') $ do
+        putStrLnErr "'tested-with:' describes an empty version range for 'GHC'"
+
+    when (isAnyVersion ghcVerConstrs') $ do
+        putStrLnErr "'tested-with:' allows /any/ 'GHC' version"
+
+    let testedGhcVersions = filter (`withinRange` ghcVerConstrs') knownGhcVersions
+
+    when (null testedGhcVersions) $ do
+        putStrLnErr "no known GHC version is allowed by the 'tested-with' specification"
+
+    let pathBits = concat [ [ "/opt/ghc/$GHCVER/bin", "/opt/cabal/$CABALVER/bin" ]
+                          , catMaybes (map pathForPackage xpkgs)
+                          , ["$PATH"]
+                          ]
+
+    -- FIXME
+    let flags = "WithGtk2HsBuildTools"
+
+    putStrLnInfo $ "Generating Travis-CI config for testing for GHC versions: " ++ (unwords $ map disp' $ testedGhcVersions)
+
+    ----------------------------------------------------------------------------
+    -- travis.yml generation starts here
+
+    putStrLn "# This file has been generated -- see https://github.com/hvr/multi-ghc-travis"
+    putStrLn "language: c"
+    putStrLn "sudo: false"
+    putStrLn ""
+    putStrLn "cache:"
+    putStrLn "  directories:"
+    putStrLn "    - $HOME/.cabsnap"
+    putStrLn "    - $HOME/.cabal/packages"
+    putStrLn ""
+    putStrLn "before_cache:"
+    putStrLn "  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/build-reports.log"
+    putStrLn "  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/00-index.tar"
+    putStrLn ""
+    putStrLn "matrix:"
+    putStrLn "  include:"
+
+    forM_ testedGhcVersions $ \gv -> do
+        let cvs = disp' (lookupCabVer gv)
+            gvs = disp' gv
+
+            xpkgs' = concatMap (',':) xpkgs
+
+        putStrLn $ concat [ "    - env: CABALVER=", cvs, " GHCVER=", gvs ]
+        putStrLn $ concat [ "      compiler: \": #GHC ", gvs, "\"" ]
+        putStrLn $ concat [ "      addons: {apt: {packages: [cabal-install-", cvs, ",ghc-", gvs, xpkgs'
+                          , "], sources: [hvr-ghc]}}" ]
+        return ()
+
+    let headGhcVers = filter isHead testedGhcVersions
+
+    unless (null headGhcVers) $ do
+        putStrLn ""
+        putStrLn "  allow_failures:"
+
+    forM_ headGhcVers $ \gv -> do
+        let cvs = disp' (lookupCabVer gv)
+            gvs = disp' gv
+        putStrLn $ concat [ "    - env: CABALVER=", cvs, " GHCVER=", gvs ]
+
+    putStrLn ""
+    putStrLn "before_install:"
+    putStrLn " - unset CC"
+    putStrLn $ " - export PATH=" ++ intercalate ":" pathBits
+
+    putStrLn ""
+
+    putStr $ unlines
+        [ "install:"
+        , " - cabal --version"
+        , " - echo \"$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]\""
+        , " - if [ -f $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz ];"
+        , "   then"
+        , "     zcat $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz >"
+        , "          $HOME/.cabal/packages/hackage.haskell.org/00-index.tar;"
+        , "   fi"
+        , " - travis_retry cabal update -v"
+        , " - sed -i 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config"
+        , " - cabal install --only-dependencies --enable-tests --enable-benchmarks --flags='" ++ flags ++ "' --dry -v > installplan.txt"
+        , " - sed -i -e '1,/^Resolving /d' installplan.txt; cat installplan.txt"
+        , ""
+        , "# check whether current requested install-plan matches cached package-db snapshot"
+        , " - if diff -u installplan.txt $HOME/.cabsnap/installplan.txt;"
+        , "   then"
+        , "     echo \"cabal build-cache HIT\";"
+        , "     rm -rfv .ghc;"
+        , "     cp -a $HOME/.cabsnap/ghc $HOME/.ghc;"
+        , "     cp -a $HOME/.cabsnap/lib $HOME/.cabsnap/share $HOME/.cabsnap/bin $HOME/.cabal/;"
+        , "   else"
+        , "     echo \"cabal build-cache MISS\";"
+        , "     rm -rf $HOME/.cabsnap;"
+        , "     mkdir -p $HOME/.ghc $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin;"
+        -- TODO: shouldn't gtk3 et al build-depend on gtk2hs-buildtools? We have to do
+        -- this incantation twice because gtk2hs-buildtools may not be installed before
+        -- the things that secretly depend on its presence. Silly.
+        , "     travis_retry cabal install --only-dependencies --enable-tests --enable-benchmarks --flags='" ++ flags ++ "';"
+        , "   fi"
+        , " "
+        , "# snapshot package-db on cache miss"
+        , " - if [ ! -d $HOME/.cabsnap ];"
+        , "   then"
+        , "      echo \"snapshotting package-db to build-cache\";"
+        , "      mkdir $HOME/.cabsnap;"
+        , "      cp -a $HOME/.ghc $HOME/.cabsnap/ghc;"
+        , "      cp -a $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin installplan.txt $HOME/.cabsnap/;"
+        , "   fi"
+        , ""
+        , "# Here starts the actual work to be performed for the package under test;"
+        , "# any command which exits with a non-zero exit code causes the build to fail."
+        , "script:"
+        , " - if [ -f configure.ac ]; then autoreconf -i; fi"
+        , " - cabal configure --enable-tests --enable-benchmarks -v2  # -v2 provides useful information for debugging"
+        , " - cabal build   # this builds all libraries and executables (including tests/benchmarks)"
+        -- FIXME
+        -- , " - cabal test"
+        , " - ./dist/setup/setup test"
+        , " - cabal check"
+        , " - cabal sdist   # tests that a source-distribution can be generated"
+        , ""
+        , "# Check that the resulting source distribution can be built & installed."
+        , "# If there are no other `.tar.gz` files in `dist`, this can be even simpler:"
+        , "# `cabal install --force-reinstalls dist/*-*.tar.gz`"
+        , " - SRC_TGZ=$(cabal info . | awk '{print $2;exit}').tar.gz &&"
+        , "   (cd dist && cabal install --force-reinstalls \"$SRC_TGZ\")"
+        , ""
+        , "# EOF"
+        ]
+
+    return ()
+  where
+    knownGhcVersions :: [Version]
+    knownGhcVersions = fmap (`Version` [])
+                       [ [7,0,1],  [7,0,2], [7,0,3], [7,0,4]
+                       , [7,2,1],  [7,2,2]
+                       , [7,4,1],  [7,4,2]
+                       , [7,6,1],  [7,6,2], [7,6,3]
+                       , [7,8,1],  [7,8,2], [7,8,3], [7,8,4]
+                       , [7,10,1]
+                       -- 7.10.2 is not in the magic whitelist at
+                       -- https://github.com/travis-ci/apt-package-whitelist/blob/master/ubuntu-precise
+                       --, [7,10,2]
+                       , [7,11] -- HEAD
+                       ]
+
+    lookupCabVer :: Version -> Version
+    lookupCabVer (Version (x:y:_) _) = maybe (error "internal error") id $ lookup (x,y) cabalVerMap
+      where
+        cabalVerMap = fmap (fmap (`Version` []))
+                      [ ((7, 0),  [1,16])
+                      , ((7, 2),  [1,16])
+                      , ((7, 4),  [1,16])
+                      , ((7, 6),  [1,16])
+                      , ((7, 8),  [1,18])
+                      , ((7,10), [1,22])
+                      , ((7,11), [1,23]) -- HEAD
+                      ]
+
+    isHead (Version (_:y:_) _) = odd (y :: Int)
+
+    disp' v | isHead v = "head"
+            | otherwise = display v
+
+    pathForPackage :: String -> Maybe String
+    pathForPackage xpkg = do
+        i <- findIndex (== '-') xpkg
+        let (p, _:ver) = splitAt i xpkg
+        guard $ p `elem` ["happy", "alex"]
+        return $ "/opt/" ++ p ++ "/" ++ ver ++ "/bin"
+