Fix #6920 Don't ignore deps with same name as sub/foreign lib

ChangeLog.md

@@ -63,6 +63,8 @@ Bug fixes:
 * The output of Stack's `path --bin-path` command is now consistent with the
   Stack environment in Stack's `exec` command and includes the `bin` directory
   of Stack's local install root directory.
+* Stack now builds packages that depend directly on packages with the same name
+  as a sublibrary or foreign library of the package.
 
 ## v3.9.3 - 2026-02-19
 

src/Stack/Package.hs

@@ -38,12 +38,10 @@ module Stack.Package
 
 import qualified Data.Map.Strict as M
 import qualified Data.Set as S
-import qualified Data.Text as T
 import           Distribution.CabalSpecVersion ( cabalSpecToVersionDigits )
 import           Distribution.Compiler
                    ( CompilerFlavor (..), PerCompilerFlavor (..) )
 import           Distribution.ModuleName ( ModuleName )
-import           Distribution.Package ( mkPackageName )
 import           Distribution.PackageDescription
                    ( Benchmark (..), BuildInfo (..), BuildType (..)
                    , CondTree (..), Condition (..), ConfVar (..)
@@ -87,7 +85,6 @@ import           Stack.Types.BuildConfig ( HasBuildConfig (..), getWorkDir )
 import           Stack.Types.CompCollection
                    ( CompCollection, collectionLookup, foldAndMakeCollection
                    , foldComponentToAnotherCollection, getBuildableSet
-                   , getBuildableSetText
                    )
 import           Stack.Types.Compiler ( ActualCompiler (..) )
 import           Stack.Types.CompilerPaths ( cabalVersionL )
@@ -762,21 +759,11 @@ processPackageDeps pkg combineResults fn =
  where
   iterator :: PackageName -> DepValue -> m a -> m a
   iterator depPackageName depValue acc
-    | shouldIgnoreDep = acc
+    -- If the name of the dependency package is the same as the package, we
+    -- ignore the former. It is possible for a dependency package to have the
+    -- same name as a named sublibrary or a named foreign library.
+    | depPackageName == pkg.name = acc
     | otherwise = combineResults <$> fn depPackageName depValue <*> acc
-   where
-    shouldIgnoreDep
-      | depPackageName == pkg.name = True
-      | depPackageName `S.member` subLibNames = True
-      | depPackageName `S.member` foreignLibNames = True
-      | otherwise = False
-     where
-      !subLibNames = asPackageNameSet (.subLibraries)
-      !foreignLibNames = asPackageNameSet (.foreignLibraries)
-      asPackageNameSet ::
-        (Package -> CompCollection component) -> Set PackageName
-      asPackageNameSet accessor =
-        S.map (mkPackageName . T.unpack) $ getBuildableSetText $ accessor pkg
 
 -- | This is a function to iterate in a monad over all of a package's
 -- dependencies (including any custom-setup ones), and yield a list of

tests/integration/tests/6920-dep-name-clash/files/.gitignore

@@ -0,0 +1,2 @@
+myPackageA.cabal
+myPackageB.cabal

tests/integration/tests/6920-dep-name-clash/files/Main.hs

@@ -0,0 +1,11 @@
+-- | Stack builds a package which depends directly on a package with the same
+-- name as a sublibrary or foreign library of that package.
+--
+-- See: https://github.com/commercialhaskell/stack/issues/6920
+
+import           StackTest
+
+main :: IO ()
+main = do
+  stack ["build", "myPackageA"]
+  stack ["build", "myPackageB"]

tests/integration/tests/6920-dep-name-clash/files/myPackageA/int/Internal.hs

@@ -0,0 +1,5 @@
+module Internal
+  ( launchMissiles
+  ) where
+
+import           Acme.Missiles ( launchMissiles )

tests/integration/tests/6920-dep-name-clash/files/myPackageA/package.yaml

@@ -0,0 +1,17 @@
+spec-version: 0.36.0
+
+# Required, otherwise Hpack picks cabal-version: 3.0 and the dependency on
+# acme-missiles is assumed to refer to the name of the internal-library.
+verbatim:
+  cabal-version: 3.4
+
+name: myPackageA
+
+dependencies:
+- base
+
+internal-libraries:
+  acme-missiles:
+    source-dirs: int
+    dependencies:
+    - acme-missiles

tests/integration/tests/6920-dep-name-clash/files/myPackageB/package.yaml

@@ -0,0 +1,20 @@
+spec-version: 0.36.0
+
+name: myPackageB
+
+dependencies:
+- base
+
+verbatim: |
+  foreign-library acme-missiles
+    type: native-shared
+    other-modules:
+        Foreign
+    build-depends:
+        base
+      , acme-missiles
+    hs-source-dirs:
+        src-foreign
+    default-language: Haskell2010
+    if os(Windows)
+      options: standalone

tests/integration/tests/6920-dep-name-clash/files/myPackageB/src-foreign/Foreign.hs

@@ -0,0 +1,5 @@
+module Foreign
+  ( launchMissiles
+  ) where
+
+import           Acme.Missiles ( launchMissiles )

tests/integration/tests/6920-dep-name-clash/files/stack.yaml

@@ -0,0 +1,8 @@
+snapshot: ghc-9.10.3
+
+packages:
+- myPackageA
+- myPackageB
+
+extra-deps:
+- acme-missiles-0.3