Disambiguate build directories.

We suffix all the build directories and files that we make with a
package name and version. As package name is a target name, there can
only be a unique one in single project and we preserve some sanity in
build environment, at least for the directories we declare and pass
around. This allows multiple `haskell_library` and `haskell_binary`
targets in a single package.

Closes #7.

haskell/haskell.bzl

@@ -9,7 +9,8 @@ load(":toolchain.bzl",
      "src_to_ext",
      "get_object_suffix",
      "get_interface_suffix",
-     "hsc2hs_args"
+     "hsc2hs_args",
+     "mk_name",
 )
 
 def _haskell_binary_impl(ctx):
@@ -26,7 +27,7 @@ def _haskell_binary_impl(ctx):
 
   depInputs += ctx.files.srcs
 
-  objDir = ctx.actions.declare_directory("objects")
+  objDir = ctx.actions.declare_directory(mk_name(ctx, "objects"))
   binObjs = [ctx.actions.declare_file(src_to_ext(ctx, s, get_object_suffix(ctx), directory=objDir))
              for s in ctx.files.srcs]
 
@@ -57,12 +58,11 @@ def _haskell_binary_impl(ctx):
   )
 
 def _haskell_library_impl(ctx):
-
-  objDir = ctx.actions.declare_directory("objects")
+  objDir = ctx.actions.declare_directory(mk_name(ctx, "objects"))
   objectFiles = [ctx.actions.declare_file(src_to_ext(ctx, s, get_object_suffix(ctx), directory=objDir))
                  for s in ctx.files.srcs]
 
-  ifaceDir = ctx.actions.declare_directory("interfaces")
+  ifaceDir = ctx.actions.declare_directory(mk_name(ctx, "interfaces"))
   interfaceFiles = [ctx.actions.declare_file(src_to_ext(ctx, s, get_interface_suffix(ctx), directory=ifaceDir))
                     for s in ctx.files.srcs ]
 
@@ -119,9 +119,10 @@ def _haskell_library_impl(ctx):
   # Make library archive; currently only static
   #
   # TODO: configurable shared &c. see various scenarios in buck
-  libDir = ctx.actions.declare_directory("lib")
-  pkgLib = ctx.actions.declare_file("{0}/lib{1}.a".format(libDir.basename, ctx.attr.name))
-
+  pkgId = "{0}-{1}".format(ctx.attr.name, ctx.attr.version)
+  libDir = ctx.actions.declare_directory(mk_name(ctx, "lib"))
+  # We need libDir because ghc-pkg wants a directory for library-dirs.
+  pkgLib = ctx.actions.declare_file("{0}/lib{1}.a".format(libDir.basename, pkgId))
   ctx.actions.run(
     inputs = objectFiles,
     outputs = [pkgLib, libDir],
@@ -131,7 +132,6 @@ def _haskell_library_impl(ctx):
   )
 
   # Create and register ghc package.
-  pkgId = "{0}-{1}".format(ctx.attr.name, ctx.attr.version)
   pkgDbDir = ctx.actions.declare_directory(pkgId)
   confFile = ctx.actions.declare_file("{0}/{1}.conf".format(pkgDbDir.basename, pkgId))
   cacheFile = ctx.actions.declare_file("package.cache", sibling=confFile)
@@ -190,7 +190,11 @@ _haskell_common_attrs = {
   ),
   "prebuiltDeps": attr.string_list(
     doc="Haskell packages which are magically available such as wired-in packages."
-  )
+  ),
+  "version": attr.string(
+    default="1.0.0",
+    doc="Package/binary version"
+  ),
 }
 
 haskell_library = rule(
@@ -199,12 +203,7 @@ haskell_library = rule(
     "conf": "%{name}-%{version}/%{name}-%{version}.conf",
     "packageCache": "%{name}-%{version}/package.cache"
   },
-  attrs = _haskell_common_attrs + {
-    "version": attr.string(
-      default="1.0.0",
-      doc="Library version"
-    ),
-  }
+  attrs = _haskell_common_attrs,
 )
 
 haskell_binary = rule(

haskell/toolchain.bzl

@@ -13,6 +13,14 @@ HaskellPackageInfo = provider(
   }
 )
 
+def mk_name(ctx, namePrefix):
+  """Make a target-unique name.
+
+  Args:
+    namePrefix: Template for the name.
+  """
+  return "{0}-{1}-{2}".format(namePrefix, ctx.attr.name, ctx.attr.version)
+
 def ghc_bin_obj_args(ctx, objDir):
   """Build arguments for Haskell binary object building.
 
@@ -173,7 +181,7 @@ def mk_registration_file(ctx, pkgId, interfaceDir, libDir):
     interfaceDir: Directory with interface files.
     libDir: Directory containing library archive(s).
   """
-  registrationFile = ctx.actions.declare_file("registration-file")
+  registrationFile = ctx.actions.declare_file(mk_name(ctx, "registration-file"))
   registrationFileDict = {
     "name": ctx.attr.name,
     "version": ctx.attr.version,
@@ -186,7 +194,7 @@ def mk_registration_file(ctx, pkgId, interfaceDir, libDir):
                                  for f in ctx.files.srcs]),
     "import-dirs": "${{pkgroot}}/{0}".format(interfaceDir.basename),
     "library-dirs": "${{pkgroot}}/{0}".format(libDir.basename),
-    "hs-libraries": ctx.attr.name,
+    "hs-libraries": pkgId,
     "depends": ", ".join([ d[HaskellPackageInfo].pkgName for d in ctx.attr.deps ])
   }
   ctx.actions.write(

tests/BUILD

@@ -10,6 +10,16 @@ haskell_binary(
     deps = ["//tests/test-lib"]
 )
 
+haskell_binary(
+  name = "two-libs-one-BUILD",
+  main = "TogetherTest.main",
+  srcs = ["TogetherTest.hs"],
+  deps = [
+    "//tests/together-lib:one",
+    "//tests/together-lib:two"
+  ]
+)
+
 [sh_test(
     name = "Run" + binary,
     srcs = ["test_binary.sh"],
@@ -18,4 +28,5 @@ haskell_binary(
     timeout="short",
 ) for binary in [
     "hello",
+    "two-libs-one-BUILD",
 ]]

tests/TogetherTest.hs

@@ -0,0 +1,7 @@
+module TogetherTest (main) where
+
+import One (one)
+import Two (two)
+
+main :: IO ()
+main = putStrLn $ "One and Two makes " ++ show (one + two)

tests/together-lib/BUILD

@@ -0,0 +1,16 @@
+package(default_visibility = ["//visibility:public"])
+
+load(
+  "@io_tweag_rules_haskell//haskell:haskell.bzl",
+  "haskell_library",
+)
+
+haskell_library(
+  name = 'one',
+  srcs = [ 'One.hs' ]
+)
+
+haskell_library(
+  name = 'two',
+  srcs = [ 'Two.hs' ]
+)

tests/together-lib/One.hs

@@ -0,0 +1,4 @@
+module One (one) where
+
+one :: Int
+one = 1

tests/together-lib/Two.hs

@@ -0,0 +1,4 @@
+module Two (two) where
+
+two :: Int
+two = 2