Fix google#185: Support and use autogen-modules.

This makes it possible to generate tarballs without generated modules
(which would be regenerated anyway when the package is build).
See tensorflow/haskell#180 for an example of the issues that causes.

docs/releasing.md

@@ -17,26 +17,8 @@ since they are intended only for use within this repository:
 - Make sure you are on a commit that has been merged upstream to `google/proto-lens`.
 
 ## Steps
-1. For each package *without* autogenerated proto modules, simply run (from the root of the repo):
+First, run `stack build` at the top level.  Then, for each package that you want to upload, run
 
         stack upload {name-of-package}
 
-  Then verify that they've been uploaded successfully by visiting `hackage.org` in a web browser.
-
-2. For packages *with* autogenerated proto-modules (currently:
-`proto-lens-protobuf-types` and `proto-lens-combinators`): these are a little
-harder to upload due to #185.  We have a script for running `sdist`:
-
-        ./release.sh
-
-  Then, for each package that should be uploaded:
-
-        cabal upload {package}/dist/{path}.tar.gz
-
-3. Finally, tag each uploaded package with its version and push it back to upstream.  For example:
-
-        git tag -a proto-lens-v0.3.0.0 -m "Release proto-lens v0.3.0.0"
-        ...
-        git remote add upstream [email protected]:google/proto-lens.git
-        git push upstream --follow-tags  # See: https://stackoverflow.com/a/26438076
-
+Then verify that they've been uploaded successfully by visiting `hackage.org` in a web browser.

proto-lens-combinators/package.yaml

@@ -45,6 +45,6 @@ tests:
       - proto-lens-protoc
       - test-framework
       - test-framework-hunit
-    other-modules:
+    generated-other-modules:
       Proto.Combinators
       Proto.Combinators_Fields

proto-lens-protobuf-types/package.yaml

@@ -32,7 +32,7 @@ dependencies:
 
 library:
   source-dirs: src
-  exposed-modules:
+  generated-exposed-modules:
     - Data.ProtoLens.Any
     - Proto.Google.Protobuf.Any
     - Proto.Google.Protobuf.Any_Fields
@@ -42,3 +42,4 @@ library:
     - Proto.Google.Protobuf.Wrappers_Fields
     - Proto.Google.Protobuf.Timestamp
     - Proto.Google.Protobuf.Timestamp_Fields
+  other-modules: []

proto-lens-protoc/src/Data/ProtoLens/Setup.hs

@@ -185,11 +185,16 @@ generatingSpecificProtos root getProtos hooks = hooks
     { buildHook = \p l h f -> generate l >> buildHook hooks p l h f
     , haddockHook = \p l h f -> generate l >> haddockHook hooks p l h f
     , replHook = \p l h f args -> generate l >> replHook hooks p l h f args
+#if !MIN_VERSION_Cabal(2,0,0)
+    -- Older versions of Cabal don't support the autogen-modules field.
+    -- Work around it by manually generating the modules and putting them
+    -- in a place where `cabal sdist` will pick them up.
     , sDistHook = \p maybe_l h f -> case maybe_l of
             Nothing -> error "Can't run protoc; run 'cabal configure' first."
             Just l -> do
                         generate l
                         sDistHook hooks (fudgePackageDesc l p) maybe_l h f
+#endif
     , postCopy = \a flags pkg lbi -> do
                   let verb = fromFlag $ copyVerbosity flags
                   let destDir = datadir (absoluteInstallDirs pkg lbi