type safe targets for properties

  * Property types have been improved to indicate what systems they target.
    This prevents using eg, Property FreeBSD on a Debian system.
    Transition guide for this sweeping API change:
    - Change "host name & foo & bar"
      to     "host name $ props & foo & bar"
    - Similarly, `propertyList` and `combineProperties` need `props`
      to be used to combine together properties; they no longer accept
      lists of properties. (If you have such a list, use `toProps`.)
    - And similarly, Chroot, Docker, and Systemd container need `props`
      to be used to combine together the properies used inside them.
    - The `os` property is removed. Instead use `osDebian`, `osBuntish`,
      or `osFreeBSD`. These tell the type checker the target OS of a host.
    - Change "Property NoInfo" to "Property UnixLike"
    - Change "Property HasInfo" to "Property (HasInfo + UnixLike)"
    - Change "RevertableProperty NoInfo" to
      "RevertableProperty UnixLike UnixLike"
    - Change "RevertableProperty HasInfo" to
      "RevertableProperty (HasInfo + UnixLike) UnixLike"
    - GHC needs {-# LANGUAGE TypeOperators #-} to use these fancy types.
      This is enabled by default for all modules in propellor.cabal. But
      if you are using propellor as a library, you may need to enable it
      manually.
    - If you know a property only works on a particular OS, like Debian
      or FreeBSD, use that instead of "UnixLike". For example:
      "Property Debian"
    - It's also possible make a property support a set of OS's, for example:
      "Property (Debian + FreeBSD)"
    - Removed `infoProperty` and `simpleProperty` constructors, instead use
      `property` to construct a Property.
    - Due to the polymorphic type returned by `property`, additional type
      signatures tend to be needed when using it. For example, this will
      fail to type check, because the type checker cannot guess what type
      you intend the intermediate property "go" to have:
        foo :: Property UnixLike
        foo = go `requires` bar
	  where
		go = property "foo" (return NoChange)
      To fix, specify the type of go:
	  	go :: Property UnixLike
    - `ensureProperty` now needs to be passed a witness to the type of the
      property it's used in.
      change this:  foo = property desc $ ... ensureProperty bar
      to this:      foo = property' desc $ \w -> ... ensureProperty w bar
    - General purpose properties like cmdProperty have type "Property UnixLike".
      When using that to run a command only available on Debian, you can
      tighten the type to only the OS that your more specific property works on.
      For example:
        upgraded :: Property Debian
        upgraded = tightenTargets (cmdProperty "apt-get" ["upgrade"])
    - Several utility functions have been renamed:
      getInfo to fromInfo
      propertyInfo to getInfo
      propertyDesc to getDesc
      propertyChildren to getChildren
  * The new `pickOS` property combinator can be used to combine different
    properties, supporting different OS's, into one Property that chooses
    which to use based on the Host's OS.
  * Re-enabled -O0 in propellor.cabal to reign in ghc's memory use handling
    these complex new types.
  * Added dependency on concurrent-output; removed embedded copy.

1 files changed, 9 insertions, 8 deletions

diff --git a/src/Propellor/Property/Obnam.hs b/src/Propellor/Property/Obnam.hs
index 666328ac..6d6f4a7f 100644
--- a/src/Propellor/Property/Obnam.hs
+++ b/src/Propellor/Property/Obnam.hs
@@ -40,7 +40,7 @@ data NumClients = OnlyClient | MultipleClients
 -- Since obnam uses a fair amount of system resources, only one obnam
 -- backup job will be run at a time. Other jobs will wait their turns to
 -- run.
-backup :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Property NoInfo
+backup :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Property DebianLike
 backup dir crontimes params numclients =
 	backup' dir crontimes params numclients
 		`requires` restored dir params
@@ -50,7 +50,7 @@ backup dir crontimes params numclients =
 --
 -- The gpg secret key will be automatically imported
 -- into root's keyring using Propellor.Property.Gpg.keyImported
-backupEncrypted :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Gpg.GpgKeyId -> Property HasInfo
+backupEncrypted :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Gpg.GpgKeyId -> Property (HasInfo + DebianLike)
 backupEncrypted dir crontimes params numclients keyid =
 	backup dir crontimes params' numclients
 		`requires` Gpg.keyImported keyid (User "root")
@@ -58,7 +58,7 @@ backupEncrypted dir crontimes params numclients keyid =
 	params' = ("--encrypt-with=" ++ Gpg.getGpgKeyId keyid) : params
 
 -- | Does a backup, but does not automatically restore.
-backup' :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Property NoInfo
+backup' :: FilePath -> Cron.Times -> [ObnamParam] -> NumClients -> Property DebianLike
 backup' dir crontimes params numclients = cronjob `describe` desc
   where
 	desc = dir ++ " backed up by obnam"
@@ -96,11 +96,12 @@ backup' dir crontimes params numclients = cronjob `describe` desc
 --
 -- The restore is performed atomically; restoring to a temp directory
 -- and then moving it to the directory.
-restored :: FilePath -> [ObnamParam] -> Property NoInfo
-restored dir params = property (dir ++ " restored by obnam") go
-	`requires` installed
+restored :: FilePath -> [ObnamParam] -> Property DebianLike
+restored dir params = go `requires` installed
   where
-	go = ifM (liftIO needsRestore)
+	desc = dir ++ " restored by obnam"
+	go :: Property DebianLike
+	go = property desc $ ifM (liftIO needsRestore)
 		( do
 			warningMessage $ dir ++ " is empty/missing; restoring from backup ..."
 			liftIO restore
@@ -152,5 +153,5 @@ keepParam ps = "--keep=" ++ intercalate "," (map go ps)
 isKeepParam :: ObnamParam -> Bool
 isKeepParam p = "--keep=" `isPrefixOf` p
 
-installed :: Property NoInfo
+installed :: Property DebianLike
 installed = Apt.installed ["obnam"]