Ninja: add support for Swift's output-file-map.json

Add an emitter for the Swift's output-map-file.json to emit the
requisite support files for Swift compilation.  This additionally
prevents the build rules for the object file emission as well to
properly support the Swift build semantics.

Source/cmNinjaTargetGenerator.cxx

@@ -915,6 +915,28 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatements()
   }
 
   this->GetBuildFileStream() << "\n";
+
+  if (!this->SwiftOutputMap.empty()) {
+    std::string const mapFilePath = this->ConvertToNinjaPath(
+      this->GeneratorTarget->GetSupportDirectory() + "/output-file-map.json");
+    std::string const targetSwiftDepsPath = [this]() -> std::string {
+      cmGeneratorTarget const* target = this->GeneratorTarget;
+      if (const char* name = target->GetProperty("Swift_DEPENDENCIES_FILE")) {
+        return name;
+      }
+      return this->ConvertToNinjaPath(target->GetSupportDirectory() + "/" +
+                                      target->GetName() + ".swiftdeps");
+    }();
+
+    // build the global target dependencies
+    // https://github.com/apple/swift/blob/master/docs/Driver.md#output-file-maps
+    Json::Value deps(Json::objectValue);
+    deps["swift-dependencies"] = targetSwiftDepsPath;
+    this->SwiftOutputMap[""] = deps;
+
+    cmGeneratedFileStream output(mapFilePath);
+    output << this->SwiftOutputMap;
+  }
 }
 
 void cmNinjaTargetGenerator::WriteObjectBuildStatement(
@@ -1131,10 +1153,14 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
 
   std::string const rspfile = objectFileName + ".rsp";
 
-  this->GetGlobalGenerator()->WriteBuild(
-    this->GetBuildFileStream(), comment, rule, outputs,
-    /*implicitOuts=*/cmNinjaDeps(), explicitDeps, implicitDeps, orderOnlyDeps,
-    vars, rspfile, commandLineLengthLimit);
+  if (language == "Swift") {
+    this->EmitSwiftDependencyInfo(source);
+  } else {
+    this->GetGlobalGenerator()->WriteBuild(
+      this->GetBuildFileStream(), comment, rule, outputs,
+      /*implicitOuts=*/cmNinjaDeps(), explicitDeps, implicitDeps,
+      orderOnlyDeps, vars, rspfile, commandLineLengthLimit);
+  }
 
   if (const char* objectOutputs = source->GetProperty("OBJECT_OUTPUTS")) {
     std::vector<std::string> outputList;
@@ -1193,6 +1219,52 @@ void cmNinjaTargetGenerator::WriteTargetDependInfo(std::string const& lang)
   tdif << tdi;
 }
 
+void cmNinjaTargetGenerator::EmitSwiftDependencyInfo(
+  cmSourceFile const* source)
+{
+  std::string const sourceFilePath =
+    this->ConvertToNinjaPath(this->GetSourceFilePath(source));
+  std::string const objectFilePath =
+    this->ConvertToNinjaPath(this->GetObjectFilePath(source));
+  std::string const swiftDepsPath = [source, objectFilePath]() -> std::string {
+    if (const char* name = source->GetProperty("Swift_DEPENDENCIES_FILE")) {
+      return name;
+    }
+    return objectFilePath + ".swiftdeps";
+  }();
+  std::string const swiftDiaPath = [source, objectFilePath]() -> std::string {
+    if (const char* name = source->GetProperty("Swift_DIAGNOSTICS_FILE")) {
+      return name;
+    }
+    return objectFilePath + ".dia";
+  }();
+  std::string const makeDepsPath = [this, source]() -> std::string {
+    cmLocalNinjaGenerator const* local = this->GetLocalGenerator();
+    std::string const objectFileName =
+      this->ConvertToNinjaPath(this->GetObjectFilePath(source));
+    std::string const objectFileDir =
+      cmSystemTools::GetFilenamePath(objectFileName);
+
+    if (this->Makefile->IsOn("CMAKE_Swift_DEPFLE_EXTNSION_REPLACE")) {
+      std::string dependFileName =
+        cmSystemTools::GetFilenameWithoutLastExtension(objectFileName) + ".d";
+      return local->ConvertToOutputFormat(objectFileDir + "/" + dependFileName,
+                                          cmOutputConverter::SHELL);
+    }
+    return local->ConvertToOutputFormat(objectFileName + ".d",
+                                        cmOutputConverter::SHELL);
+  }();
+
+  // build the source file mapping
+  // https://github.com/apple/swift/blob/master/docs/Driver.md#output-file-maps
+  Json::Value entry = Json::Value(Json::objectValue);
+  entry["object"] = objectFilePath;
+  entry["dependencies"] = makeDepsPath;
+  entry["swift-dependencies"] = swiftDepsPath;
+  entry["diagnostics"] = swiftDiaPath;
+  SwiftOutputMap[sourceFilePath] = entry;
+}
+
 void cmNinjaTargetGenerator::ExportObjectCompileCommand(
   std::string const& language, std::string const& sourceFileName,
   std::string const& objectDir, std::string const& objectFileName,

Source/cmNinjaTargetGenerator.h

@@ -5,6 +5,8 @@
 
 #include "cmConfigure.h" // IWYU pragma: keep
 
+#include "cm_jsoncpp_value.h"
+
 #include "cmCommonTargetGenerator.h"
 #include "cmGlobalNinjaGenerator.h"
 #include "cmNinjaTypes.h"
@@ -128,6 +130,8 @@ protected:
   void WriteObjectBuildStatement(cmSourceFile const* source);
   void WriteTargetDependInfo(std::string const& lang);
 
+  void EmitSwiftDependencyInfo(cmSourceFile const* source);
+
   void ExportObjectCompileCommand(
     std::string const& language, std::string const& sourceFileName,
     std::string const& objectDir, std::string const& objectFileName,
@@ -171,7 +175,10 @@ private:
   cmLocalNinjaGenerator* LocalGenerator;
   /// List of object files for this target.
   cmNinjaDeps Objects;
+  // Fortran Support
   std::map<std::string, cmNinjaDeps> DDIFiles;
+  // Swift Support
+  Json::Value SwiftOutputMap;
   std::vector<cmCustomCommand const*> CustomCommands;
   cmNinjaDeps ExtraFiles;
 };