[clangd] Use CommandMangler in TestTU

This makes testing setup look closer to production.

Differential Revision: https://reviews.llvm.org/D106535

clang-tools-extra/clangd/unittests/TestTU.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "TestTU.h"
+#include "CompileCommands.h"
 #include "Compiler.h"
 #include "Diagnostics.h"
 #include "TestFS.h"
@@ -56,6 +57,9 @@ ParseInputs TestTU::inputs(MockFS &FS) const {
   // Put the file name at the end -- this allows the extra arg (-xc++) to
   // override the language setting.
   Argv.push_back(FullFilename);
+
+  auto Mangler = CommandMangler::forTests();
+  Mangler.adjust(Inputs.CompileCommand.CommandLine);
   Inputs.CompileCommand.Filename = FullFilename;
   Inputs.CompileCommand.Directory = testRoot();
   Inputs.Contents = Code;

clang/lib/Frontend/CreateInvocationFromCommandLine.cpp

@@ -10,15 +10,17 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Frontend/Utils.h"
 #include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Driver/Action.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
-#include "clang/Driver/Action.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/Utils.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/Host.h"
 using namespace clang;
@@ -37,7 +39,10 @@ std::unique_ptr<CompilerInvocation> clang::createInvocationFromCommandLine(
   SmallVector<const char *, 16> Args(ArgList.begin(), ArgList.end());
 
   // FIXME: Find a cleaner way to force the driver into restricted modes.
-  Args.push_back("-fsyntax-only");
+  Args.insert(
+      llvm::find_if(
+          Args, [](const char *Elem) { return llvm::StringRef(Elem) == "--"; }),
+      "-fsyntax-only");
 
   // FIXME: We shouldn't have to pass in the path info.
   driver::Driver TheDriver(Args[0], llvm::sys::getDefaultTargetTriple(), *Diags,