refactor(stack): Generalize filtering out the "ghc" package

The filtering of the "ghc" package is not covered by tests and it is
unkown whether it is needed with the current tooling versions. It seems
relatively safe to assume that the "ghc" package has not been referenced
by any scope back when the filtering was implemented.

Remove filtering "ghc" explicitly in favor of filtering out all
non-referenced packages, which solves the original problem in a more
general way.

Signed-off-by: Frank Viernau <frank_viernau@epam.com>

plugins/package-managers/stack/src/main/kotlin/Stack.kt

@@ -108,17 +108,10 @@ class Stack(
         val testDependencies = listDependencies(workingDir, TEST_SCOPE_NAME)
         val benchDependencies = listDependencies(workingDir, BENCH_SCOPE_NAME)
 
-        val dependencyPackageMap = buildMap {
-            (externalDependencies + testDependencies + benchDependencies).filterNot {
-                // Do not add the project as a package.
-                it.isProject()
-            }.forEach { dependency ->
-                val pkg = dependency.toPackage()
-
-                // Do not add the Glasgow Haskell Compiler (GHC) as a package.
-                if (pkg.id.name != "ghc") this[dependency] = pkg
-            }
-        }
+        val dependencyPackageMap = (externalDependencies + testDependencies + benchDependencies).filterNot {
+            // Do not add the project as a package.
+            it.isProject()
+        }.associateWith { it.toPackage() }
 
         fun List<String>.toPackageReferences(): Set<PackageReference> =
             mapNotNullTo(mutableSetOf()) { name ->
@@ -138,6 +131,9 @@ class Stack(
             Scope(BENCH_SCOPE_NAME, benchDependencies.getProjectDependencies().toPackageReferences())
         )
 
+        val referencedPackageIds = scopes.flatMapTo(mutableSetOf()) { it.collectDependencies() }
+        val packages = dependencyPackageMap.values.filterTo(mutableSetOf()) { it.id in referencedPackageIds }
+
         val project = Project(
             id = projectId,
             definitionFilePath = VersionControlSystem.getPathInfo(definitionFile).path,
@@ -149,7 +145,7 @@ class Stack(
             scopeDependencies = scopes
         )
 
-        return listOf(ProjectAnalyzerResult(project, dependencyPackageMap.values.toSet()))
+        return listOf(ProjectAnalyzerResult(project, packages))
     }
 
     private fun runStack(workingDir: File, vararg command: String): ProcessCapture {