[Explicit Module Builds] Add basic thread-safety to InterModuleDependencyOracle

Author: artemcm

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

@@ -14,16 +14,20 @@
   /// An API to allow clients to accumulate InterModuleDependencyGraphs across mutiple main modules/targets
   /// into a single collection of discovered modules.
   func mergeModules(from dependencyGraph: InterModuleDependencyGraph) throws {
-    for (moduleId, moduleInfo) in dependencyGraph.modules {
-      try InterModuleDependencyGraph.mergeModule(moduleId, moduleInfo, into: &modules)
+    try self.lock.withLock {
+      for (moduleId, moduleInfo) in dependencyGraph.modules {
+        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)
+    try self.lock.withLock {
+      for (moduleId, moduleInfo) in moduleInfoMap {
+        try InterModuleDependencyGraph.mergeModule(moduleId, moduleInfo, into: &modules)
+      }
     }
   }
 }

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

@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import TSCBasic
+
 // An inter-module dependency oracle, responsible for responding to queries about
 // dependencies of a given module, caching already-discovered dependencies along the way.
 //
@@ -26,13 +28,15 @@
 public class InterModuleDependencyOracle {
   /// Query the ModuleInfo of a module with a given ID
   @_spi(Testing) public func getModuleInfo(of moduleId: ModuleDependencyId) -> ModuleInfo? {
-    return modules[moduleId]
+    self.lock.withLock {
+      return modules[moduleId]
+    }
   }
 
   /// Query the direct dependencies of a module with a given ID
   @_spi(Testing) public func getDependencies(of moduleId: ModuleDependencyId)
   -> [ModuleDependencyId]? {
-    return modules[moduleId]?.directDependencies
+    return getModuleInfo(of: moduleId)?.directDependencies
   }
 
   // TODO: This will require a SwiftDriver entry-point for scanning a module given
@@ -44,6 +48,8 @@ public class InterModuleDependencyOracle {
   //                          commandLine: [Job.ArgTemplate]) -> InterModuleDependencyGraph {}
   //
 
+  internal let lock = Lock()
+
   /// The complete set of modules discovered so far, spanning potentially multiple targets
   internal var modules: ModuleInfoMap = [:]
 

Sources/SwiftDriver/Jobs/Planning.swift

@@ -407,6 +407,7 @@ extension Driver {
     }
 
     // Re-scan Clang modules at all the targets they will be built against.
+    // TODO: Should be deprecated once switched over to libSwiftScan
     try resolveVersionedClangDependencies(dependencyGraph: &dependencyGraph)
 
     // Set dependency modules' paths to be saved in the module cache.