[Explicit Module Builds] Add extra adapter to handle previous ModuleInfoMap-based API used by SwiftPM

Author: artemcm

Sources/SwiftDriver/Driver/Driver.swift

@@ -377,6 +377,14 @@ public struct Driver {
       self.interModuleDependencyOracle = dependencyOracle
     } else {
       self.interModuleDependencyOracle = InterModuleDependencyOracle()
+
+      // This is a shim for backwards-compatibility with ModuleInfoMap-based API
+      // used by SwiftPM
+      if let externalArtifacts = externalBuildArtifacts {
+        if !externalArtifacts.1.isEmpty {
+          try self.interModuleDependencyOracle.mergeModules(from: externalArtifacts.1)
+        }
+      }
     }
 
     let outputFileMap: OutputFileMap?

Sources/SwiftDriver/Explicit Module Builds/Inter Module Dependencies/CommonDependencyOperations.swift

@@ -18,6 +18,14 @@
       try InterModuleDependencyGraph.mergeModule(moduleId, moduleInfo, into: &modules)
     }
   }
+
+  // This is a backwards-compatibility shim to handle existing ModuleInfoMap-based API
+  // used by SwiftPM
+  func mergeModules(from moduleInfoMap: ModuleInfoMap) throws {
+    for (moduleId, moduleInfo) in moduleInfoMap {
+      try InterModuleDependencyGraph.mergeModule(moduleId, moduleInfo, into: &modules)
+    }
+  }
 }
 
 public extension InterModuleDependencyGraph {

Sources/SwiftDriver/Explicit Module Builds/PlaceholderDependencyResolution.swift

@@ -45,7 +45,6 @@ import Foundation
                                                using dependencyOracle: InterModuleDependencyOracle)
   throws {
     let externalTargetModulePathMap = externalBuildArtifacts.0
-    //let externalModuleInfoMap = externalBuildArtifacts.1
     let placeholderFilter : (ModuleDependencyId) -> Bool = {
       if case .swiftPlaceholder(_) = $0 {
         return true