Clean up topologicalSort in PackageGraph

Author: plemarquand

Sources/PackageGraph/ModulesGraph.swift

@@ -13,7 +13,6 @@
 import OrderedCollections
 import PackageLoading
 import PackageModel
-import TSCBasic
 
 import protocol Basics.FileSystem
 import class Basics.ObservabilityScope
@@ -270,7 +269,7 @@ public struct ModulesGraph {
 
         for module in rootModules where module.type == .executable {
             // Find all dependencies of this module within its package. Note that we do not traverse plugin usages.
-            let dependencies = try topologicalSortIdentifiable(module.dependencies, successors: {
+            let dependencies = try topologicalSort(module.dependencies, successors: {
                 $0.dependencies.compactMap{ $0.module }.filter{ $0.type != .plugin }.map{ .module($0, conditions: []) }
             }).compactMap({ $0.module })
 
@@ -403,7 +402,7 @@ enum GraphError: Error {
 ///
 /// - Complexity: O(v + e) where (v, e) are the number of vertices and edges
 /// reachable from the input nodes via the relation.
-func topologicalSortIdentifiable<T: Identifiable>(
+fileprivate func topologicalSort<T: Identifiable>(
     _ nodes: [T], successors: (T) throws -> [T]
 ) throws -> [T] {
     // Implements a topological sort via recursion and reverse postorder DFS.
@@ -497,3 +496,12 @@ public func loadModulesGraph(
         modulesFilter: nil
     )
 }
+
+fileprivate extension Array {
+    /// Create a dictionary with given sequence of elements.
+    func spm_createDictionary<Key: Hashable, Value>(
+        _ uniqueKeysWithValues: (Element) -> (Key, Value)
+    ) -> [Key: Value] {
+        return Dictionary(uniqueKeysWithValues: self.map(uniqueKeysWithValues))
+    }
+}