[Explicit Module Builds] Fix topological sort of inter-module dependency graph

to account for Swift overlay dependencies

Author: artemcm

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift

@@ -57,7 +57,15 @@ extension InterModuleDependencyGraph {
   var topologicalSorting: [ModuleDependencyId] {
     get throws {
       try topologicalSort(Array(modules.keys),
-                          successors: { try moduleInfo(of: $0).directDependencies! })
+                          successors: {
+        var dependencies: [ModuleDependencyId] = []
+        let moduleInfo = try moduleInfo(of: $0)
+        dependencies.append(contentsOf: moduleInfo.directDependencies ?? [])
+        if case .swift(let swiftModuleDetails) = moduleInfo.details {
+          dependencies.append(contentsOf: swiftModuleDetails.swiftOverlayDependencies ?? [])
+        }
+        return dependencies
+      })
     }
   }
 
@@ -71,7 +79,7 @@ extension InterModuleDependencyGraph {
   ///     T(v) = T(v) ∪ T(w)
   ///   }
   /// }
-  func computeTransitiveClosure() throws -> [ModuleDependencyId : Set<ModuleDependencyId>] {
+  @_spi(Testing) public func computeTransitiveClosure() throws -> [ModuleDependencyId : Set<ModuleDependencyId>] {
     let topologicalIdList = try self.topologicalSorting
     // This structure will contain the final result
     var transitiveClosureMap =

Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift

@@ -1791,6 +1791,18 @@ final class ExplicitModuleBuildTests: XCTestCase {
     XCTAssertTrue(scanJobCommand.contains(swiftInputWithoutSpace))
   }
 
+  func testDependencyGraphTransitiveClosure() throws {
+    let moduleDependencyGraph =
+          try JSONDecoder().decode(
+            InterModuleDependencyGraph.self,
+            from: ModuleDependenciesInputs.simpleDependencyGraphInputWithSwiftOverlayDep.data(using: .utf8)!)
+    let reachabilityMap = try moduleDependencyGraph.computeTransitiveClosure()
+    let mainModuleDependencies = try XCTUnwrap(reachabilityMap[.swift("simpleTestModule")])
+    let aModuleDependencies = try XCTUnwrap(reachabilityMap[.swift("A")])
+    XCTAssertTrue(mainModuleDependencies.contains(.swift("B")))
+    XCTAssertTrue(aModuleDependencies.contains(.swift("B")))
+  }
+
   func testExplicitSwiftModuleMap() throws {
     let jsonExample : String = """
     [

Tests/SwiftDriverTests/Inputs/ExplicitModuleDependencyBuildInputs.swift

@@ -515,6 +515,112 @@ enum ModuleDependenciesInputs {
     """
   }
 
+  static var simpleDependencyGraphInputWithSwiftOverlayDep: String {
+    """
+    {
+      "mainModuleName": "simpleTestModule",
+      "modules": [
+        {
+          "swift": "A"
+        },
+        {
+          "modulePath": "A.swiftmodule",
+          "sourceFiles": [
+          ],
+          "directDependencies": [
+            {
+              "clang": "B"
+            }
+          ],
+          "details": {
+            "swift": {
+              "moduleInterfacePath": "A.swiftmodule/A.swiftinterface",
+              "isFramework": false,
+              "extraPcmArgs": [
+                "-Xcc",
+                "-fapinotes-swift-version=5"
+              ],
+              "swiftOverlayDependencies": [
+                {
+                  "swift": "B"
+                }
+              ]
+            }
+          }
+        },
+        {
+          "swift": "simpleTestModule"
+        },
+        {
+          "modulePath": "simpleTestModule.swiftmodule",
+          "sourceFiles": [
+            "/main/simpleTestModule.swift"
+          ],
+          "directDependencies": [
+            {
+              "swift": "A"
+            },
+          ],
+          "details": {
+            "swift": {
+              "isFramework": false,
+              "extraPcmArgs": [
+                "-Xcc",
+                "-fapinotes-swift-version=5"
+              ]
+            }
+          }
+        },
+        {
+          "swift" : "B"
+        },
+        {
+          "modulePath" : "B.swiftmodule",
+          "sourceFiles": [
+          ],
+          "directDependencies" : [
+    
+          ],
+          "details" : {
+            "swift" : {
+              "moduleInterfacePath": "B.swiftmodule/B.swiftinterface",
+              "isFramework": false,
+              "extraPcmArgs": [
+                "-Xcc",
+                "-fapinotes-swift-version=5"
+              ],
+            }
+          }
+        },
+        {
+          "clang": "B"
+        },
+        {
+          "modulePath": "B.pcm",
+          "sourceFiles": [
+            "/B/module.map",
+            "/B/include/b.h"
+          ],
+          "directDependencies": [
+          ],
+          "details": {
+            "clang": {
+              "moduleMapPath": "/B/module.map",
+              "contextHash": "2QEMRLNY63H2N",
+              "commandLine": [
+                "-remove-preceeding-explicit-module-build-incompatible-options",
+                "-fno-implicit-modules",
+                "-emit-module",
+                "-fmodule-name=c_simd"
+              ]
+            }
+          }
+        }
+      ]
+    }
+    """
+  }
+
   static var mergeGraphInput2: String {
     """
     {