[clang] [clang][Dependency Scanning] Refactor Scanning Compiler Instance Initialization (PR #161300)

[Jan Svoboda via cfe-commits]

================
@@ -97,51 +84,24 @@ llvm::Error DependencyScanningWorker::computeDependencies(
     StringRef ModuleName) {
   // Capture the emitted diagnostics and report them to the client
   // in the case of a failure.
-  std::string DiagnosticOutput;
-  llvm::raw_string_ostream DiagnosticsOS(DiagnosticOutput);
-  auto DiagOpts = createDiagOptions(CommandLine);
-  TextDiagnosticPrinter DiagPrinter(DiagnosticsOS, *DiagOpts);
+  TextDiagnosticsPrinterWithOutput DiagPrinterWithOS(CommandLine);
 
   if (computeDependencies(WorkingDirectory, CommandLine, Consumer, Controller,
-                          DiagPrinter, ModuleName))
+                          DiagPrinterWithOS.DiagPrinter, ModuleName))
     return llvm::Error::success();
-  return llvm::make_error<llvm::StringError>(DiagnosticsOS.str(),
-                                             llvm::inconvertibleErrorCode());
+  return llvm::make_error<llvm::StringError>(
+      DiagPrinterWithOS.DiagnosticsOS.str(), llvm::inconvertibleErrorCode());
 }
 
 static bool forEachDriverJob(
     ArrayRef<std::string> ArgStrs, DiagnosticsEngine &Diags,
     IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
     llvm::function_ref<bool(const driver::Command &Cmd)> Callback) {
-  SmallVector<const char *, 256> Argv;
-  Argv.reserve(ArgStrs.size());
-  for (const std::string &Arg : ArgStrs)
-    Argv.push_back(Arg.c_str());
-
-  std::unique_ptr<driver::Driver> Driver = std::make_unique<driver::Driver>(
-      Argv[0], llvm::sys::getDefaultTargetTriple(), Diags,
-      "clang LLVM compiler", FS);
-  Driver->setTitle("clang_based_tool");
-
-  llvm::BumpPtrAllocator Alloc;
-  bool CLMode = driver::IsClangCL(
-      driver::getDriverMode(Argv[0], ArrayRef(Argv).slice(1)));
-
-  if (llvm::Error E =
-          driver::expandResponseFiles(Argv, CLMode, Alloc, FS.get())) {
-    Diags.Report(diag::err_drv_expand_response_file)
-        << llvm::toString(std::move(E));
-    return false;
-  }
-
-  const std::unique_ptr<driver::Compilation> Compilation(
-      Driver->BuildCompilation(llvm::ArrayRef(Argv)));
+  // Compilation owns a reference to the Driver, hence we need to
----------------
jansvoboda11 wrote:

```suggestion
  // Compilation holds a non-owning reference to the Driver, hence we need to
```

https://github.com/llvm/llvm-project/pull/161300