separate Hs-Source-Dirs for binaries

This is a trick I only just learned about, see
https://stackoverflow.com/questions/6711151/how-to-avoid-recompiling-in-this-cabal-file#6711739

Significantly increased propellor build speed when your config.hs is in
a fork of the propellor repository, by avoiding redundant builds of
propellor library.

Also avoids needing to list all the build deps 3 times.

Also avoids cabal 2.x wanting every module to be listed 3 times.

Note that the bulk of wrapper.hs had to move into the propellor library,
since that code depended on stuff not exposed by the library.

This commit was sponsored by Henrik Riomar on Patreon.

5 files changed, 35 insertions, 36 deletions

diff --git a/debian/changelog b/debian/changelog
index 9af87222..e75d7f8f 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -2,6 +2,9 @@ propellor (5.3.5) UNRELEASED; urgency=medium
 
   * Apt.stdSourcesList now adds stable-updates suite
     Thanks, Sean Whitton
+  * Significantly increased propellor build speed when your config.hs
+    is in a fork of the propellor repository, by avoiding redundant builds
+    of propellor library.
 
  -- Joey Hess <id@joeyh.name>  Wed, 18 Apr 2018 10:12:21 -0400
 
diff --git a/src/propellor-config.hs b/executables/propellor-config.hs
index e3af968e..e3af968e 120000
--- a/src/propellor-config.hs
+++ b/executables/propellor-config.hs
diff --git a/executables/wrapper.hs b/executables/wrapper.hs
new file mode 100644
index 00000000..3a6cee3a
--- /dev/null
+++ b/executables/wrapper.hs
@@ -0,0 +1,6 @@
+module Main where
+
+import Propellor.Wrapper
+
+main :: IO ()
+main = runWrapper
diff --git a/propellor.cabal b/propellor.cabal
index 18d28db3..4e4102d0 100644
--- a/propellor.cabal
+++ b/propellor.cabal
@@ -35,38 +35,6 @@ Description:
  .
  It is configured using haskell.
 
-Executable propellor
-  Default-Language: Haskell98
-  Main-Is: wrapper.hs
-  GHC-Options: -threaded -Wall -fno-warn-tabs -O0
-  if impl(ghc >= 8.0)
-    GHC-Options: -fno-warn-redundant-constraints
-  Default-Extensions: TypeOperators
-  Hs-Source-Dirs: src
-  Build-Depends:
-    -- propellor needs to support the ghc shipped in Debian stable,
-    -- and also only depends on packages in Debian stable.
-    base >= 4.5, base < 5,
-    directory, filepath, IfElse, process, bytestring, hslogger, split,
-    unix, unix-compat, ansi-terminal, containers (>= 0.5), network, async,
-    time, mtl, transformers, exceptions (>= 0.6), stm, text, hashable
-  Other-Modules:
-    Propellor.DotDir
-
-Executable propellor-config
-  Default-Language: Haskell98
-  Main-Is: propellor-config.hs
-  GHC-Options: -threaded -Wall -fno-warn-tabs -O0
-  if impl(ghc >= 8.0)
-    GHC-Options: -fno-warn-redundant-constraints
-  Default-Extensions: TypeOperators
-  Hs-Source-Dirs: src
-  Build-Depends:
-    base >= 4.5, base < 5,
-    directory, filepath, IfElse, process, bytestring, hslogger, split,
-    unix, unix-compat, ansi-terminal, containers (>= 0.5), network, async,
-    time, mtl, transformers, exceptions (>= 0.6), stm, text, hashable
-
 Library
   Default-Language: Haskell98
   GHC-Options: -Wall -fno-warn-tabs -O0
@@ -75,6 +43,8 @@ Library
   Default-Extensions: TypeOperators
   Hs-Source-Dirs: src
   Build-Depends:
+    -- propellor needs to support the ghc shipped in Debian stable,
+    -- and also only depends on packages in Debian stable.
     base >= 4.5, base < 5,
     directory, filepath, IfElse, process, bytestring, hslogger, split,
     unix, unix-compat, ansi-terminal, containers (>= 0.5), network, async,
@@ -83,6 +53,7 @@ Library
   Exposed-Modules:
     Propellor
     Propellor.Base
+    Propellor.DotDir
     Propellor.Location
     Propellor.Property
     Propellor.Property.Aiccu
@@ -211,6 +182,7 @@ Library
     Propellor.Types.ResultCheck
     Propellor.Types.Singletons
     Propellor.Types.ZFS
+    Propellor.Wrapper
   Other-Modules:
     Propellor.Bootstrap
     Propellor.Git
@@ -254,6 +226,23 @@ Library
     System.Console.Concurrent
     System.Console.Concurrent.Internal
     System.Process.Concurrent
+    Paths_propellor
+
+Executable propellor-config
+  Default-Language: Haskell98
+  Hs-Source-Dirs: executables
+  Main-Is: propellor-config.hs
+  GHC-Options: -threaded -Wall -fno-warn-tabs -O0
+  if impl(ghc >= 8.0)
+    GHC-Options: -fno-warn-redundant-constraints
+  Default-Extensions: TypeOperators
+  Build-Depends: propellor, base
+
+Executable propellor
+  Default-Language: Haskell98
+  Hs-Source-Dirs: executables
+  Main-Is: wrapper.hs
+  Build-Depends: propellor, base
 
 source-repository head
   type: git
diff --git a/src/wrapper.hs b/src/Propellor/Wrapper.hs
index 20b4d8c6..f399b2cf 100644
--- a/src/wrapper.hs
+++ b/src/Propellor/Wrapper.hs
@@ -1,4 +1,5 @@
--- | Wrapper program for propellor distribution.
+-- | This module is used to implement a wrapper program for propellor
+-- distribution.
 --
 -- Distributions should install this program into PATH.
 -- (Cabal builds it as dist/build/propellor/propellor).
@@ -10,7 +11,7 @@
 -- If ./config.hs exists and looks like a propellor config file, 
 -- it instead builds and runs in the current working directory.
 
-module Main where
+module Propellor.Wrapper (runWrapper) where
 
 import Propellor.DotDir
 import Propellor.Message
@@ -30,8 +31,8 @@ import Control.Monad.IfElse
 import Control.Applicative
 import Prelude
 
-main :: IO ()
-main = withConcurrentOutput $ do
+runWrapper :: IO ()
+runWrapper = withConcurrentOutput $ do
 	useFileSystemEncoding
 	go =<< getArgs
   where