Implement file+noindex:///local/repositories

Resolve #6359

`preferred-versions` are left out for now.
It shouldn't be difficult to add, but needs work nevertheless.

In addtition
- change the index cache to use `Distribution.Utils.Structured`,
  making Binary instances generically derived.
- separate Distribution.Client.HashValue into own module.
  This allows to use HashValue for hashing the part of localRepoPath
  (breaks module dependency cycle).

Almost as a feature generated 01-index.cache is never updated.
If you change the contents of the directory, you have to purge
01-index.cache file yourself.

Cabal/Distribution/Utils/Structured.hs

@@ -49,8 +49,10 @@ module Distribution.Utils.Structured (
     -- | These functions operate like @binary@'s counterparts,
     -- but the serialised version has a structure hash in front.
     structuredEncode,
+    structuredEncodeFile,
     structuredDecode,
     structuredDecodeOrFailIO,
+    structuredDecodeFileOrFail,
     -- * Structured class
     Structured (structure),
     MD5,
@@ -262,6 +264,10 @@ structuredEncode
   => a -> LBS.ByteString
 structuredEncode x = Binary.encode (Tag :: Tag a, x)
 
+-- | Lazily serialise a value to a file
+structuredEncodeFile :: (Binary.Binary a, Structured a) => FilePath -> a -> IO ()
+structuredEncodeFile f = LBS.writeFile f . structuredEncode
+
 -- | Structured 'Binary.decode'.
 -- Decode a value from a lazy 'LBS.ByteString', reconstructing the original structure.
 -- Throws pure exception on invalid inputs.
@@ -280,6 +286,10 @@ structuredDecodeOrFailIO bs =
     handler (ErrorCall str) = return $ Left str
 #endif
 
+-- | Lazily reconstruct a value previously written to a file.
+structuredDecodeFileOrFail :: (Binary.Binary a, Structured a) => FilePath -> IO (Either String a)
+structuredDecodeFileOrFail f = structuredDecodeOrFailIO =<< LBS.readFile f
+
 -------------------------------------------------------------------------------
 -- Helper data
 -------------------------------------------------------------------------------

Cabal/doc/installing-packages.rst

@@ -57,7 +57,7 @@ The name of the repository is given on the first line, and can be
 anything; packages downloaded from this repository will be cached under
 ``~/.cabal/packages/hackage.haskell.org`` (or whatever name you specify;
 you can change the prefix by changing the value of
-``remote-repo-cache``). If you want, you can configure multiple
+:cfg-field:`remote-repo-cache`). If you want, you can configure multiple
 repositories, and ``cabal`` will combine them and be able to download
 packages from any of them.
 
@@ -97,7 +97,32 @@ received were the right ones. How that is done is however outside the
 scope of ``cabal`` proper.
 
 More information about the security infrastructure can be found at
-https://github.com/well-typed/hackage-security.
+https://github.com/haskell/hackage-security.
+
+Local no-index repositories
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+It's possible to use a directory of `.tar.gz` package files as a local package
+repository.
+
+::
+
+    repository my-local-repository
+      url: file+noindex:///absolute/path/to/directory
+
+``cabal`` will construct the index automatically from the
+``package-name-version.tar.gz`` files in the directory, and will use optional
+corresponding ``package-name-version.cabal`` files as new revisions.
+
+The index is cached inside the given directory. If the directory is not
+writable, you can append ``#shared-cache`` fragment to the URI,
+then the cache will be stored inside the :cfg-field:`remote-repo-cache` directory.
+The part of the path will be used to determine the cache key part.
+
+.. note::
+    The URI scheme ``file:`` is interpreted as a remote repository,
+    as described in the previous sections, thus requiring manual construction
+    of ``01-index.tar`` file.
 
 Legacy repositories
 ^^^^^^^^^^^^^^^^^^^
@@ -120,7 +145,7 @@ although, in (and only in) the specific case of Hackage, the URL
 ``http://hackage.haskell.org/packages/archive`` will be silently
 translated to ``http://hackage.haskell.org/``.
 
-The second kind of legacy repositories are so-called “local”
+The second kind of legacy repositories are so-called “(legacy) local”
 repositories:
 
 ::

cabal-install/Distribution/Client/CmdUpdate.hs

@@ -186,7 +186,8 @@ updateRepo :: Verbosity -> UpdateFlags -> RepoContext -> (Repo, IndexState)
 updateRepo verbosity _updateFlags repoCtxt (repo, indexState) = do
   transport <- repoContextGetTransport repoCtxt
   case repo of
-    RepoLocal{..} -> return ()
+    RepoLocal{} -> return ()
+    RepoLocalNoIndex{} -> return ()
     RepoRemote{..} -> do
       downloadResult <- downloadIndex transport verbosity
                         repoRemote repoLocalDir

cabal-install/Distribution/Client/Config.hs

@@ -41,7 +41,8 @@ module Distribution.Client.Config (
     userConfigUpdate,
     createDefaultConfigFile,
 
-    remoteRepoFields
+    remoteRepoFields,
+    postProcessRepo,
   ) where
 
 import Language.Haskell.Extension ( Language(Haskell2010) )
@@ -50,7 +51,7 @@ import Distribution.Deprecated.ViewAsFieldDescr
          ( viewAsFieldDescr )
 
 import Distribution.Client.Types
-         ( RemoteRepo(..), Username(..), Password(..), emptyRemoteRepo
+         ( RemoteRepo(..), LocalRepo (..), Username(..), Password(..), emptyRemoteRepo
          , AllowOlder(..), AllowNewer(..), RelaxDeps(..), isRelaxDeps
          )
 import Distribution.Client.BuildReports.Types
@@ -64,7 +65,7 @@ import Distribution.Client.Setup
          , InstallFlags(..), installOptions, defaultInstallFlags
          , UploadFlags(..), uploadCommand
          , ReportFlags(..), reportCommand
-         , showRepo, parseRepo, readRepo )
+         , showRemoteRepo, parseRemoteRepo, readRemoteRepo )
 import Distribution.Client.CmdInstall.ClientInstallFlags
          ( ClientInstallFlags(..), defaultClientInstallFlags
          , clientInstallOptions )
@@ -92,7 +93,7 @@ import Distribution.Deprecated.ParseUtils
          , locatedErrorMsg, showPWarning
          , readFields, warning, lineNo
          , simpleField, listField, spaceListField
-         , parseFilePathQ, parseOptCommaList, parseTokenQ )
+         , parseFilePathQ, parseOptCommaList, parseTokenQ, syntaxError)
 import Distribution.Client.ParseUtils
          ( parseFields, ppFields, ppSection )
 import Distribution.Client.HttpUtils
@@ -252,6 +253,7 @@ instance Semigroup SavedConfig where
         globalRemoteRepos       = lastNonEmptyNL globalRemoteRepos,
         globalCacheDir          = combine globalCacheDir,
         globalLocalRepos        = lastNonEmptyNL globalLocalRepos,
+        globalLocalNoIndexRepos = lastNonEmptyNL globalLocalNoIndexRepos,
         globalLogsDir           = combine globalLogsDir,
         globalWorldFile         = combine globalWorldFile,
         globalRequireSandbox    = combine globalRequireSandbox,
@@ -1034,7 +1036,7 @@ deprecatedFieldDescriptions :: [FieldDescr SavedConfig]
 deprecatedFieldDescriptions =
   [ liftGlobalFlag $
     listField "repos"
-      (Disp.text . showRepo) parseRepo
+      (Disp.text . showRemoteRepo) parseRemoteRepo
       (fromNubList . globalRemoteRepos)
       (\rs cfg -> cfg { globalRemoteRepos = toNubList rs })
   , liftGlobalFlag $
@@ -1117,19 +1119,25 @@ parseConfig src initial = \str -> do
   let init0   = savedInitFlags config
       user0   = savedUserInstallDirs config
       global0 = savedGlobalInstallDirs config
-  (remoteRepoSections0, haddockFlags, initFlags, user, global, paths, args) <-
+  (remoteRepoSections0, localRepoSections0, haddockFlags, initFlags, user, global, paths, args) <-
     foldM parseSections
-          ([], savedHaddockFlags config, init0, user0, global0, [], [])
+          ([], [], savedHaddockFlags config, init0, user0, global0, [], [])
           knownSections
 
   let remoteRepoSections =
           reverse
         . nubBy ((==) `on` remoteRepoName)
         $ remoteRepoSections0
 
+  let localRepoSections =
+          reverse
+        . nubBy ((==) `on` localRepoName)
+        $ localRepoSections0
+
   return . fixConfigMultilines $ config {
     savedGlobalFlags       = (savedGlobalFlags config) {
        globalRemoteRepos   = toNubList remoteRepoSections,
+       globalLocalNoIndexRepos = toNubList localRepoSections,
        -- the global extra prog path comes from the configure flag prog path
        globalProgPathExtra = configProgramPathExtra (savedConfigureFlags config)
        },
@@ -1185,68 +1193,92 @@ parseConfig src initial = \str -> do
     parse = parseFields (configFieldDescriptions src
                       ++ deprecatedFieldDescriptions) initial
 
-    parseSections (rs, h, i, u, g, p, a)
-                 (ParseUtils.Section _ "repository" name fs) = do
+    parseSections (rs, ls, h, i, u, g, p, a)
+                 (ParseUtils.Section lineno "repository" name fs) = do
       r' <- parseFields remoteRepoFields (emptyRemoteRepo name) fs
-      when (remoteRepoKeyThreshold r' > length (remoteRepoRootKeys r')) $
-        warning $ "'key-threshold' for repository " ++ show (remoteRepoName r')
-               ++ " higher than number of keys"
-      when (not (null (remoteRepoRootKeys r'))
-            && remoteRepoSecure r' /= Just True) $
-        warning $ "'root-keys' for repository " ++ show (remoteRepoName r')
-               ++ " non-empty, but 'secure' not set to True."
-      return (r':rs, h, i, u, g, p, a)
-
-    parseSections (rs, h, i, u, g, p, a)
+      r'' <- postProcessRepo lineno name r'
+      case r'' of
+          Left local   -> return (rs,        local:ls, h, i, u, g, p, a)
+          Right remote -> return (remote:rs, ls,       h, i, u, g, p, a)
+
+    parseSections (rs, ls, h, i, u, g, p, a)
                  (ParseUtils.F lno "remote-repo" raw) = do
-      let mr' = readRepo raw
+      let mr' = readRemoteRepo raw
       r' <- maybe (ParseFailed $ NoParse "remote-repo" lno) return mr'
-      return (r':rs, h, i, u, g, p, a)
+      return (r':rs, ls, h, i, u, g, p, a)
 
-    parseSections accum@(rs, h, i, u, g, p, a)
+    parseSections accum@(rs, ls, h, i, u, g, p, a)
                  (ParseUtils.Section _ "haddock" name fs)
       | name == ""        = do h' <- parseFields haddockFlagsFields h fs
-                               return (rs, h', i, u, g, p, a)
+                               return (rs, ls, h', i, u, g, p, a)
       | otherwise         = do
           warning "The 'haddock' section should be unnamed"
           return accum
 
-    parseSections accum@(rs, h, i, u, g, p, a)
+    parseSections accum@(rs, ls, h, i, u, g, p, a)
                  (ParseUtils.Section _ "init" name fs)
       | name == ""        = do i' <- parseFields initFlagsFields i fs
-                               return (rs, h, i', u, g, p, a)
+                               return (rs, ls, h, i', u, g, p, a)
       | otherwise         = do
           warning "The 'init' section should be unnamed"
           return accum
 
-    parseSections accum@(rs, h, i, u, g, p, a)
+    parseSections accum@(rs, ls, h, i, u, g, p, a)
                   (ParseUtils.Section _ "install-dirs" name fs)
       | name' == "user"   = do u' <- parseFields installDirsFields u fs
-                               return (rs, h, i, u', g, p, a)
+                               return (rs, ls, h, i, u', g, p, a)
       | name' == "global" = do g' <- parseFields installDirsFields g fs
-                               return (rs, h, i, u, g', p, a)
+                               return (rs, ls, h, i, u, g', p, a)
       | otherwise         = do
           warning "The 'install-paths' section should be for 'user' or 'global'"
           return accum
       where name' = lowercase name
-    parseSections accum@(rs, h, i, u, g, p, a)
+    parseSections accum@(rs, ls, h, i, u, g, p, a)
                  (ParseUtils.Section _ "program-locations" name fs)
       | name == ""        = do p' <- parseFields withProgramsFields p fs
-                               return (rs, h, i, u, g, p', a)
+                               return (rs, ls, h, i, u, g, p', a)
       | otherwise         = do
           warning "The 'program-locations' section should be unnamed"
           return accum
-    parseSections accum@(rs, h, i, u, g, p, a)
+    parseSections accum@(rs, ls, h, i, u, g, p, a)
                   (ParseUtils.Section _ "program-default-options" name fs)
       | name == ""        = do a' <- parseFields withProgramOptionsFields a fs
-                               return (rs, h, i, u, g, p, a')
+                               return (rs, ls, h, i, u, g, p, a')
       | otherwise         = do
           warning "The 'program-default-options' section should be unnamed"
           return accum
     parseSections accum f = do
       warning $ "Unrecognized stanza on line " ++ show (lineNo f)
       return accum
 
+postProcessRepo :: Int -> String -> RemoteRepo -> ParseResult (Either LocalRepo RemoteRepo)
+postProcessRepo lineno reponame repo0 = do
+    when (null reponame) $
+        syntaxError lineno $ "a 'repository' section requires the "
+                          ++ "repository name as an argument"
+
+    case uriScheme (remoteRepoURI repo0) of
+        -- TODO: check that there are no authority, query or fragment
+        -- Note: the trailing colon is important
+        "file+noindex:" -> do
+            let uri = remoteRepoURI repo0
+            return $ Left $ LocalRepo reponame (uriPath uri) (uriFragment uri == "#shared-cache")
+
+        _              -> do
+            let repo = repo0 { remoteRepoName = reponame }
+
+            when (remoteRepoKeyThreshold repo > length (remoteRepoRootKeys repo)) $
+                warning $ "'key-threshold' for repository "
+                    ++ show (remoteRepoName repo)
+                    ++ " higher than number of keys"
+
+            when (not (null (remoteRepoRootKeys repo)) && remoteRepoSecure repo /= Just True) $
+                warning $ "'root-keys' for repository "
+                    ++ show (remoteRepoName repo)
+                    ++ " non-empty, but 'secure' not set to True."
+
+            return $ Right repo
+
 showConfig :: SavedConfig -> String
 showConfig = showConfigWithComments mempty
 
@@ -1297,7 +1329,7 @@ installDirsFields = map viewAsFieldDescr installDirsOptions
 
 ppRemoteRepoSection :: RemoteRepo -> RemoteRepo -> Doc
 ppRemoteRepoSection def vals = ppSection "repository" (remoteRepoName vals)
-        remoteRepoFields (Just def) vals
+    remoteRepoFields (Just def) vals
 
 remoteRepoFields :: [FieldDescr RemoteRepo]
 remoteRepoFields =

cabal-install/Distribution/Client/FetchUtils.hs

@@ -177,6 +177,7 @@ fetchRepoTarball verbosity' repoCtxt repo pkgid = do
 
     downloadRepoPackage = case repo of
       RepoLocal{..} -> return (packageFile repo pkgid)
+      RepoLocalNoIndex{..} -> return (packageFile repo pkgid)
 
       RepoRemote{..} -> do
         transport <- repoContextGetTransport repoCtxt
@@ -292,6 +293,7 @@ packageFile repo pkgid = packageDir repo pkgid
 -- the tarball for a given @PackageIdentifer@ is stored.
 --
 packageDir :: Repo -> PackageId -> FilePath
+packageDir (RepoLocalNoIndex (LocalRepo _ dir _) _) _pkgid = dir
 packageDir repo pkgid = repoLocalDir repo
                     </> display (packageName    pkgid)
                     </> display (packageVersion pkgid)