Fix non-buildable bug in Cabal <= 1.22

Author: snoyberg

ChangeLog.md

@@ -1,5 +1,21 @@
 # Changelog
 
+## Unreleased changes
+
+Release notes:
+
+Major changes:
+
+Behaviour changes:
+
+Other enhancements:
+
+Bug fixes:
+
+* For versions of Cabal before 1.24, ensure that the dependencies of
+  non-buildable components are part of the build plan to work around an old
+  Cabal bug.
+
 ## v1.6.1
 
 Major changes:

src/Stack/BuildPlan.hs

@@ -198,7 +198,7 @@ gpdPackageDeps
     -> Map FlagName Bool
     -> Map PackageName VersionRange
 gpdPackageDeps gpd cv platform flags =
-    Map.filterWithKey (const . (/= name)) (packageDependencies pkgDesc)
+    Map.filterWithKey (const . (/= name)) (packageDependencies cv pkgDesc)
     where
         name = gpdPackageName gpd
         -- Since tests and benchmarks are both enabled, doesn't matter

src/Stack/Package.hs

@@ -356,7 +356,7 @@ packageFromPackageDescription packageConfig pkgFlags (PackageDescriptionPair pkg
     pkgId = package pkg
     name = fromCabalPackageName (pkgName pkgId)
     deps = M.filterWithKey (const . not . isMe) (M.union
-        (packageDependencies pkg)
+        (packageDependencies (packageConfigCompilerVersion packageConfig) pkg)
         -- We include all custom-setup deps - if present - in the
         -- package deps themselves. Stack always works with the
         -- invariant that there will be a single installed package
@@ -602,12 +602,36 @@ getBuildComponentDir Nothing = Nothing
 getBuildComponentDir (Just name) = parseRelDir (name FilePath.</> (name ++ "-tmp"))
 
 -- | Get all dependencies of the package (buildable targets only).
-packageDependencies :: PackageDescription -> Map PackageName VersionRange
-packageDependencies pkg =
+--
+-- Note that for Cabal versions 1.22 and earlier, there is a bug where
+-- Cabal requires dependencies for non-buildable components to be
+-- present. We're going to use GHC version as a proxy for Cabal
+-- library version in this case for simplicity, so we'll check for GHC
+-- being 7.10 or earlier. This obviously makes our function a lot more
+-- fun to write...
+packageDependencies
+  :: CompilerVersion 'CVActual
+  -> PackageDescription
+  -> Map PackageName VersionRange
+packageDependencies ghcVersion pkg' =
   M.fromListWith intersectVersionRanges $
   map (depName &&& depRange) $
   concatMap targetBuildDepends (allBuildInfo' pkg) ++
   maybe [] setupDepends (setupBuildInfo pkg)
+  where
+    pkg
+      | getGhcVersion ghcVersion >= $(mkVersion "8.0") = pkg'
+      -- Set all components to buildable. Only need to worry about
+      -- library, exe, test, and bench, since others didn't exist in
+      -- older Cabal versions
+      | otherwise = pkg'
+        { library = (\c -> c { libBuildInfo = go (libBuildInfo c) }) <$> library pkg'
+        , executables = (\c -> c { buildInfo = go (buildInfo c) }) <$> executables pkg'
+        , testSuites = (\c -> c { testBuildInfo = go (testBuildInfo c) }) <$> testSuites pkg'
+        , benchmarks = (\c -> c { benchmarkBuildInfo = go (benchmarkBuildInfo c) }) <$> benchmarks pkg'
+        }
+
+    go bi = bi { buildable = True }
 
 -- | Get all dependencies of the package (buildable targets only).
 --

src/Stack/Snapshot.hs

@@ -769,7 +769,7 @@ calculate gpd platform compilerVersion loc flags hide options =
       , lpiGhcOptions = options
       , lpiPackageDeps = Map.map fromVersionRange
                        $ Map.filterWithKey (const . (/= name))
-                       $ packageDependencies pd
+                       $ packageDependencies compilerVersion pd
       , lpiProvidedExes =
             Set.fromList
           $ map (ExeName . T.pack . C.unUnqualComponentName . C.exeName)

test/integration/tests/cabal-non-buildable-bug/Main.hs

@@ -0,0 +1,18 @@
+import StackTest
+
+main :: IO ()
+main = do
+  -- Newer Cabal: dry run and building should succeed, because they'll
+  -- both ignore the do-not-build
+  writeFile "stack.yaml" "resolver: ghc-8.0.2"
+  stack ["build", "--dry-run"]
+  stack ["build"]
+
+  -- Older Cabal: both should fail, because they'll both try to
+  -- include the non-buildable component. If there's a regression, the
+  -- dry run will succeed (because Stack will use the proper logic)
+  -- and build will fail (because Cabal will be using its broken
+  -- logic).
+  writeFile "stack.yaml" "resolver: ghc-7.10.3"
+  stackErr ["build"]
+  stackErr ["build", "--dry-run"]

test/integration/tests/cabal-non-buildable-bug/files/.gitignore

@@ -0,0 +1,2 @@
+stack.yaml
+foo.cabal

test/integration/tests/cabal-non-buildable-bug/files/package.yaml

@@ -0,0 +1,14 @@
+name: foo
+version: "0"
+
+dependencies:
+- base
+
+library: {}
+
+executables:
+  not-built:
+    main: Main.hs
+    dependencies:
+    - does-not-exist
+    buildable: false