[clang-rename] Fix handling of unchanged files

Fix the output of clang-rename for the files without modifications.
Update the code in clang-reorder-fields/tool/ClangReorderFields.cpp 
to avoid inconsistency.

Example:
a.h:
struct A {};
a.cpp:
#include "a.h"
int main() { return 0; }

Before the changes the output looks like this:
clang-rename -qualified-name=A -new-name=B a.cpp
<<<<<INVALID SOURCE LOCATION>>>>>

Test plan: make -j8 check-clang-tools

Differential revision: https://reviews.llvm.org/D24634

llvm-svn: 281826

clang-tools-extra/clang-rename/tool/ClangRename.cpp

@@ -222,7 +222,7 @@ int main(int argc, const char **argv) {
     Tool.applyAllReplacements(Rewrite);
     for (const auto &File : Files) {
       const auto *Entry = FileMgr.getFile(File);
-      auto ID = Sources.translateFile(Entry);
+      const auto ID = Sources.getOrCreateFileID(Entry, SrcMgr::C_User);
       Rewrite.getEditBuffer(ID).write(outs());
     }
   }

clang-tools-extra/clang-reorder-fields/tool/ClangReorderFields.cpp

@@ -80,13 +80,8 @@ int main(int argc, const char **argv) {
 
   for (const auto &File : Files) {
     const auto *Entry = FileMgr.getFile(File);
-    const auto ID = Sources.translateFile(Entry);
-    // The method Rewriter::getRewriteBufferFor returns nullptr if
-    // the file has not been changed.
-    if (const auto *RB = Rewrite.getRewriteBufferFor(ID))
-      RB->write(outs());
-    else
-      outs() << Sources.getMemoryBufferForFile(Entry)->getBuffer();
+    const auto ID = Sources.getOrCreateFileID(Entry, SrcMgr::C_User);
+    Rewrite.getEditBuffer(ID).write(outs());
   }
 
   return ExitCode;

clang-tools-extra/test/clang-rename/IncludeHeaderWithSymbol.cpp

@@ -0,0 +1,10 @@
+#include "Inputs/HeaderWithSymbol.h"
+
+int main() {
+  return 0; // CHECK: {{^  return 0;}}
+}
+
+// Test 1.
+// The file IncludeHeaderWithSymbol.cpp doesn't contain the symbol Foo
+// and is expected to be written to stdout without modifications
+// RUN: clang-rename -qualified-name=Foo -new-name=Bar %s -- | FileCheck %s

clang-tools-extra/test/clang-rename/Inputs/HeaderWithSymbol.h

@@ -0,0 +1 @@
+struct Foo {};