Use the VFS from the CompilerInvocation by default

Summary:
The CompilerInstance should create its default VFS from its CompilerInvocation. Right now the
user has to manually create the VFS before creating the FileManager even though
`-ivfsoverlay file.yaml` was passed via the CompilerInvocation (which is exactly how we worked
around this issue in `FrontendAction.cpp` so far).

This patch uses the invocation's VFS by default and also tests this behavior now from the
point of view of a program that uses the clang API.

Reviewers: benlangmuir, v.g.vassilev

Reviewed By: v.g.vassilev

Subscribers: mgorny, cfe-commits, v.g.vassilev

Differential Revision: https://reviews.llvm.org/D37416

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313049 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 75 insertions, 0 deletions

diff --git a/unittests/Frontend/CMakeLists.txt b/unittests/Frontend/CMakeLists.txt
index 81a98280fd..e3a21f57ba 100644
--- a/unittests/Frontend/CMakeLists.txt
+++ b/unittests/Frontend/CMakeLists.txt
@@ -4,6 +4,7 @@ set(LLVM_LINK_COMPONENTS
 
 add_clang_unittest(FrontendTests
   ASTUnitTest.cpp
+  CompilerInstanceTest.cpp
   FrontendActionTest.cpp
   CodeGenActionTest.cpp
   PCHPreambleTest.cpp
diff --git a/unittests/Frontend/CompilerInstanceTest.cpp b/unittests/Frontend/CompilerInstanceTest.cpp
new file mode 100644
index 0000000000..30775bc3f7
--- /dev/null
+++ b/unittests/Frontend/CompilerInstanceTest.cpp
@@ -0,0 +1,74 @@
+//===- unittests/Frontend/CompilerInstanceTest.cpp - CI tests -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/CompilerInvocation.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace clang;
+
+namespace {
+
+TEST(CompilerInstance, DefaultVFSOverlayFromInvocation) {
+  // Create a temporary VFS overlay yaml file.
+  int FD;
+  SmallString<256> FileName;
+  ASSERT_FALSE(sys::fs::createTemporaryFile("vfs", "yaml", FD, FileName));
+  tool_output_file File(FileName, FD);
+
+  SmallString<256> CurrentPath;
+  sys::fs::current_path(CurrentPath);
+  sys::fs::make_absolute(CurrentPath, FileName);
+
+  // Mount the VFS file itself on the path 'virtual.file'. Makes this test
+  // a bit shorter than creating a new dummy file just for this purpose.
+  const std::string CurrentPathStr = CurrentPath.str();
+  const std::string FileNameStr = FileName.str();
+  const char *VFSYaml = "{ 'version': 0, 'roots': [\n"
+                        "  { 'name': '%s',\n"
+                        "    'type': 'directory',\n"
+                        "    'contents': [\n"
+                        "      { 'name': 'vfs-virtual.file', 'type': 'file',\n"
+                        "        'external-contents': '%s'\n"
+                        "      }\n"
+                        "    ]\n"
+                        "  }\n"
+                        "]}\n";
+  File.os() << format(VFSYaml, CurrentPathStr.c_str(), FileName.c_str());
+  File.os().flush();
+
+  // Create a CompilerInvocation that uses this overlay file.
+  const std::string VFSArg = "-ivfsoverlay" + FileNameStr;
+  const char *Args[] = {"clang", VFSArg.c_str(), "-xc++", "-"};
+
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(new DiagnosticOptions());
+
+  std::shared_ptr<CompilerInvocation> CInvok =
+      createInvocationFromCommandLine(Args, Diags);
+
+  if (!CInvok)
+    FAIL() << "could not create compiler invocation";
+  // Create a minimal CompilerInstance which should use the VFS we specified
+  // in the CompilerInvocation (as we don't explicitly set our own).
+  CompilerInstance Instance;
+  Instance.setDiagnostics(Diags.get());
+  Instance.setInvocation(CInvok);
+  Instance.createFileManager();
+
+  // Check if the virtual file exists which means that our VFS is used by the
+  // CompilerInstance.
+  ASSERT_TRUE(Instance.getFileManager().getFile("vfs-virtual.file"));
+}
+
+} // anonymous namespace