[Dependency Scanner] Add import-prescan handling to batch scanning

Author: artemcm

lib/FrontendTool/ScanDependencies.cpp

@@ -659,6 +659,8 @@ static bool scanModuleDependencies(CompilerInstance &instance,
                                               FEOpts.PrebuiltModuleCachePath,
                                               FEOpts.SerializeModuleInterfaceDependencyHashes,
                                               FEOpts.shouldTrackSystemDependencies());
+  std::error_code EC;
+  llvm::raw_fd_ostream out(outputPath, EC, llvm::sys::fs::F_None);
   Optional<ModuleDependencies> rootDeps;
   if (isClang) {
     // Loading the clang module using Clang importer.
@@ -677,6 +679,12 @@ static bool scanModuleDependencies(CompilerInstance &instance,
   allModules.insert({moduleName.str(), isClang ? ModuleDependenciesKind::Clang:
     ModuleDependenciesKind::Swift});
 
+  // Output module prescan.
+  if (FEOpts.ImportPrescan) {
+    writePrescanJSON(out, rootDeps.getValue());
+    return false;
+  }
+
   // Explore the dependencies of every module.
   for (unsigned currentModuleIdx = 0;
        currentModuleIdx < allModules.size();
@@ -687,8 +695,6 @@ static bool scanModuleDependencies(CompilerInstance &instance,
     allModules.insert(discoveredModules.begin(), discoveredModules.end());
   }
   // Write out the JSON description.
-  std::error_code EC;
-  llvm::raw_fd_ostream out(outputPath, EC, llvm::sys::fs::F_None);
   writeJSON(out, instance, cache, ASTDelegate, allModules.getArrayRef());
   return false;
 }

test/ScanDependencies/batch_prescan.swift

@@ -0,0 +1,22 @@
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/inputs)
+// RUN: %empty-directory(%t/outputs)
+// RUN: mkdir -p %t/clang-module-cache
+
+// RUN: echo "[{" > %/t/inputs/input.json
+// RUN: echo "\"swiftModuleName\": \"F\"," >> %/t/inputs/input.json
+// RUN: echo "\"arguments\": \"-target x86_64-apple-macosx10.9\"," >> %/t/inputs/input.json
+// RUN: echo "\"output\": \"%/t/outputs/F.swiftmodule.json\"" >> %/t/inputs/input.json
+// RUN: echo "}]" >> %/t/inputs/input.json
+
+// RUN: %target-swift-frontend -scan-dependencies -import-prescan -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 -import-objc-header %S/Inputs/CHeaders/Bridging.h -swift-version 4 -batch-scan-input-file %/t/inputs/input.json
+
+// Check the contents of the JSON output
+// RUN: %FileCheck %s -check-prefix=CHECK-SWIFT < %t/outputs/F.swiftmodule.json
+
+// CHECK-SWIFT: {
+// CHECK-SWIFT-NEXT:"imports": [
+// CHECK-SWIFT-NEXT:  "Swift",
+// CHECK-SWIFT-NEXT:  "F",
+// CHECK-SWIFT-NEXT:  "SwiftOnoneSupport"
+// CHECK-SWIFT-NEXT:]