[Dependency scanning] Emit make-style dependency files.

If requested, produce the normal make-style dependency file from the
fast dependency scanner, using the same dependency-tracking
infrastructure.

Author: DougGregor

lib/FrontendTool/FrontendTool.cpp

@@ -923,10 +923,6 @@ static Optional<bool> dumpASTIfNeeded(const CompilerInvocation &Invocation,
   case FrontendOptions::ActionType::EmitImportedModules:
     emitImportedModules(Context, Instance.getMainModule(), opts);
     break;
-
-  case FrontendOptions::ActionType::ScanDependencies:
-    scanDependencies(Context, Instance.getMainModule(), opts);
-    break;
   }
   return Context.hadError();
 }
@@ -1270,10 +1266,16 @@ static bool performCompile(CompilerInstance &Instance,
   if (Action == FrontendOptions::ActionType::Parse)
     return Context.hadError();
 
+  if (Action == FrontendOptions::ActionType::ScanDependencies) {
+    scanDependencies(Context, Instance.getMainModule(),
+                     Instance.getDependencyTracker(), opts);
+  }
+
   (void)emitMakeDependenciesIfNeeded(Context.Diags,
                                      Instance.getDependencyTracker(), opts);
 
-  if (Action == FrontendOptions::ActionType::ResolveImports)
+  if (Action == FrontendOptions::ActionType::ResolveImports ||
+      Action == FrontendOptions::ActionType::ScanDependencies)
     return Context.hadError();
 
   if (observer)

lib/FrontendTool/ScanDependencies.cpp

@@ -283,6 +283,7 @@ static void writeJSON(llvm::raw_ostream &out,
 }
 
 bool swift::scanDependencies(ASTContext &Context, ModuleDecl *mainModule,
+                             DependencyTracker *depTracker,
                              const FrontendOptions &opts) {
 
   std::string path = opts.InputsAndOutputs.getSingleOutputFilename();
@@ -353,6 +354,29 @@ bool swift::scanDependencies(ASTContext &Context, ModuleDecl *mainModule,
   // Write out the JSON description.
   writeJSON(out, Context, cache, allModules.getArrayRef());
 
+  // Update the dependency tracker.
+  if (depTracker) {
+    for (auto module : allModules) {
+      auto deps = cache.findDependencies(module.first, module.second);
+      if (!deps)
+        continue;
+
+      if (auto swiftDeps = deps->getAsSwiftModule()) {
+        if (auto swiftInterfaceFile = swiftDeps->swiftInterfaceFile)
+          depTracker->addDependency(*swiftInterfaceFile, /*IsSystem=*/false);
+        for (const auto &sourceFile : swiftDeps->sourceFiles)
+          depTracker->addDependency(sourceFile, /*IsSystem=*/false);
+        for (const auto &bridgingSourceFile : swiftDeps->bridgingSourceFiles)
+          depTracker->addDependency(bridgingSourceFile, /*IsSystem=*/false);
+      } else {
+        auto clangDeps = deps->getAsClangModule();
+        depTracker->addDependency(clangDeps->moduleMapFile, /*IsSystem=*/false);
+        for (const auto &sourceFile : clangDeps->fileDependencies)
+          depTracker->addDependency(sourceFile, /*IsSystem=*/false);
+      }
+    }
+  }
+
   // This process succeeds regardless of whether any errors occurred.
   // FIXME: We shouldn't need this, but it's masking bugs in our scanning
   // logic where we don't create a fresh context when scanning Swift interfaces

lib/FrontendTool/ScanDependencies.h

@@ -16,11 +16,13 @@
 namespace swift {
 
 class ASTContext;
+class DependencyTracker;
 class FrontendOptions;
 class ModuleDecl;
 
 /// Scans the dependencies of \c mainModule.
 bool scanDependencies(ASTContext &Context, ModuleDecl *mainModule,
+                      DependencyTracker *depTracker,
                       const FrontendOptions &opts);
 
 } // end namespace swift

test/ScanDependencies/module_deps.swift

@@ -1,7 +1,9 @@
 // RUN: %empty-directory(%t)
 // RUN: mkdir -p %t/clang-module-cache
-// RUN: %target-swift-frontend -scan-dependencies -module-cache-path %t/clang-module-cache %s -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift
+// RUN: %target-swift-frontend -scan-dependencies -module-cache-path %t/clang-module-cache %s -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift -emit-dependencies -emit-dependencies-path %t/deps.d
+
 // RUN: %FileCheck %s < %t/deps.json
+// RUN: %FileCheck %s -check-prefix CHECK-MAKE-DEPS < %t/deps.d
 
 import C
 import E
@@ -73,3 +75,11 @@ import E
 
 /// --------Clang module SwiftShims
 // CHECK-LABEL: "modulePath": "SwiftShims.pcm",
+
+
+// Check make-style dependencies
+// CHECK-MAKE-DEPS: module_deps.swift
+// CHECK-MAKE-DEPS-SAME: Swift.swiftmodule
+// CHECK-MAKE-DEPS-SAME: A.swiftinterface
+// CHECK-MAKE-DEPS-SAME: B.h
+// CHECK-MAKE-DEPS-SAME: module.modulemap