[Explicit Module Builds] Refactor placeholder dependency resolution to use the dependency oracle

Author: artemcm

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

@@ -47,8 +47,8 @@ public class InterModuleDependencyOracle {
   /// The complete set of modules discovered so far, spanning potentially multiple targets
   internal var modules: ModuleInfoMap = [:]
 
-  /// Override the default initializer's access level for test access
-  @_spi(Testing) public init() {}
+  /// Allow external clients to instantiate the oracle
+  public init() {}
 }
 
 // This is a shim for backwards-compatibility with existing API used by SwiftPM.

Sources/SwiftDriver/Explicit Module Builds/PlaceholderDependencyResolution.swift

@@ -41,10 +41,11 @@ import Foundation
   // which the driver will then resolve using B's full dependency graph provided by the client.
 
   /// Resolve all placeholder dependencies using external dependency information provided by the client
-  mutating func resolvePlaceholderDependencies(using externalBuildArtifacts: ExternalBuildArtifacts)
+  mutating func resolvePlaceholderDependencies(for externalBuildArtifacts: ExternalBuildArtifacts,
+                                               using dependencyOracle: InterModuleDependencyOracle)
   throws {
     let externalTargetModulePathMap = externalBuildArtifacts.0
-    let externalModuleInfoMap = externalBuildArtifacts.1
+    //let externalModuleInfoMap = externalBuildArtifacts.1
     let placeholderFilter : (ModuleDependencyId) -> Bool = {
       if case .swiftPlaceholder(_) = $0 {
         return true
@@ -61,7 +62,7 @@ import Foundation
       }
       try resolveTargetPlaceholder(placeholderId: moduleId,
                                    placeholderPath: placeholderModulePath,
-                                   externalModuleInfoMap: externalModuleInfoMap)
+                                   dependencyOracle: dependencyOracle)
     }
 
     // Process remaining placeholders until there are none left
@@ -70,17 +71,17 @@ import Foundation
       let moduleId = placeholderModules.first!
       let swiftModuleId = ModuleDependencyId.swift(moduleId.moduleName)
 
-      guard externalModuleInfoMap[swiftModuleId] != nil else {
+      guard dependencyOracle.getModuleInfo(of: swiftModuleId) != nil else {
         throw Driver.Error.missingExternalDependency(moduleId.moduleName)
       }
-      let moduleInfo = externalModuleInfoMap[swiftModuleId]!
+      let moduleInfo = dependencyOracle.getModuleInfo(of: swiftModuleId)!
 
       // Insert the resolved module, replacing the placeholder.
       try Self.mergeModule(swiftModuleId, moduleInfo, into: &modules)
 
       // Traverse and add all of this external module's dependencies to the current graph.
       try resolvePlaceholderModuleDependencies(moduleId: swiftModuleId,
-                                               externalModuleInfoMap: externalModuleInfoMap)
+                                               dependencyOracle: dependencyOracle)
 
       // Update the set of remaining placeholders to resolve
       placeholderModules = modules.keys.filter(placeholderFilter)
@@ -92,7 +93,7 @@ fileprivate extension InterModuleDependencyGraph {
   /// Resolve a placeholder dependency that is an external target.
   mutating func resolveTargetPlaceholder(placeholderId: ModuleDependencyId,
                                          placeholderPath: AbsolutePath,
-                                         externalModuleInfoMap: ModuleInfoMap)
+                                         dependencyOracle: InterModuleDependencyOracle)
   throws {
     // For this placeholder dependency, generate a new module info containing only the pre-compiled
     // module path, and insert it into the current module's dependency graph,
@@ -119,15 +120,15 @@ fileprivate extension InterModuleDependencyGraph {
     let swiftPrebuiltModuleId = ModuleDependencyId.swiftPrebuiltExternal(placeholderId.moduleName)
 
     let externalModuleId: ModuleDependencyId
-    if externalModuleInfoMap[swiftModuleId] != nil {
+    if dependencyOracle.getModuleInfo(of: swiftModuleId) != nil {
       externalModuleId = swiftModuleId
-    } else if externalModuleInfoMap[swiftPrebuiltModuleId] != nil {
+    } else if dependencyOracle.getModuleInfo(of: swiftPrebuiltModuleId) != nil {
       externalModuleId = swiftPrebuiltModuleId
     } else {
       throw Driver.Error.missingExternalDependency(placeholderId.moduleName)
     }
 
-    let externalModuleInfo = externalModuleInfoMap[externalModuleId]!
+    let externalModuleInfo = dependencyOracle.getModuleInfo(of: externalModuleId)!
     let newExternalModuleDetails =
       SwiftPrebuiltExternalModuleDetails(compiledModulePath: placeholderPath.description)
     let newInfo = ModuleInfo(modulePath: placeholderPath.description,
@@ -140,13 +141,14 @@ fileprivate extension InterModuleDependencyGraph {
 
     // Traverse and add all of this external target's dependencies to the current graph.
     try resolvePlaceholderModuleDependencies(moduleId: externalModuleId,
-                                             externalModuleInfoMap: externalModuleInfoMap)
+                                             dependencyOracle: dependencyOracle)
   }
 
   /// Resolve all dependencies of a placeholder module (direct and transitive), but merging them into the current graph.
   mutating func resolvePlaceholderModuleDependencies(moduleId: ModuleDependencyId,
-                                                     externalModuleInfoMap: ModuleInfoMap) throws {
-    guard let resolvingModuleInfo = externalModuleInfoMap[moduleId] else {
+                                                     dependencyOracle: InterModuleDependencyOracle)
+  throws {
+    guard let resolvingModuleInfo = dependencyOracle.getModuleInfo(of: moduleId) else {
       throw Driver.Error.missingExternalDependency(moduleId.moduleName)
     }
 
@@ -157,7 +159,7 @@ fileprivate extension InterModuleDependencyGraph {
     while let currentId = toVisit[currentIndex...].first {
       currentIndex += 1
       visited.insert(currentId)
-      guard let currentInfo = externalModuleInfoMap[currentId] else {
+      guard let currentInfo = dependencyOracle.getModuleInfo(of: currentId) else {
         throw Driver.Error.missingExternalDependency(currentId.moduleName)
       }
 

Sources/SwiftDriver/Jobs/Planning.swift

@@ -395,7 +395,8 @@ extension Driver {
 
     // Resolve placeholder dependencies in the dependency graph, if any.
     if externalBuildArtifacts != nil {
-      try dependencyGraph.resolvePlaceholderDependencies(using: externalBuildArtifacts!)
+      try dependencyGraph.resolvePlaceholderDependencies(for: externalBuildArtifacts!,
+                                                         using: dependencyOracle)
     }
 
     // Re-scan Clang modules at all the targets they will be built against.

Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift

@@ -204,10 +204,10 @@ final class ExplicitModuleBuildTests: XCTestCase {
             try JSONDecoder().decode(
               InterModuleDependencyGraph.self,
               from: ModuleDependenciesInputs.bPlaceHolderInput.data(using: .utf8)!)
-
       let targetModulePathMap: ExternalTargetModulePathMap =
         [ModuleDependencyId.swiftPlaceholder("B"):AbsolutePath("/Somewhere/B.swiftmodule")]
-      let externalModuleInfoMap: ModuleInfoMap = inputDependencyGraph.modules
+      let dependencyOracle = InterModuleDependencyOracle()
+      try dependencyOracle.mergeModules(from: inputDependencyGraph)
 
       // Construct a module dependency graph that will contain .swiftPlaceholder("B"),
       // .swiftPlaceholder("Swift"), .swiftPlaceholder("SwiftOnoneSupport")
@@ -224,12 +224,13 @@ final class ExplicitModuleBuildTests: XCTestCase {
                                              fileSystem: localFileSystem,
                                              env: ProcessEnv.vars)
       var driver = try Driver(args: commandLine, executor: executor,
-                              externalBuildArtifacts: (targetModulePathMap, externalModuleInfoMap))
+                              externalBuildArtifacts: (targetModulePathMap, [:]),
+                              interModuleDependencyOracle: dependencyOracle)
 
 
       // Plan explicit dependency jobs, after resolving placeholders to actual dependencies.
-      try moduleDependencyGraph.resolvePlaceholderDependencies(
-        using: (targetModulePathMap, externalModuleInfoMap))
+      try moduleDependencyGraph.resolvePlaceholderDependencies(for: (targetModulePathMap, [:]),
+                                                               using: dependencyOracle)
 
       // Ensure the graph no longer contains any placeholders
       XCTAssertFalse(moduleDependencyGraph.modules.keys.contains {
@@ -239,7 +240,7 @@ final class ExplicitModuleBuildTests: XCTestCase {
         return false
       })
 
-      let dependencyOracle = InterModuleDependencyOracle()
+      // Merge the resolved version of the graph into the oracle
       try dependencyOracle.mergeModules(from: moduleDependencyGraph)
       driver.explicitDependencyBuildPlanner =
         try ExplicitDependencyBuildPlanner(mainModuleId: .swift("A"),