[clang-format] Assert that filenames are not empty

[MyDeveloperDay]

Summary

Adds asserts to catch empty filenames, which otherwise will cause a crash in SourceManager.
The clang-format tool now outputs an error if an empty filename is used.
Fixes bug: 34667

[MyDeveloperDay]

Thanks for the patch, I'm sorry it's taken so long sometimes items get lost...This looks to still be relevant, I think you'll need to rebase but it LGTM

$ clang-format --assume-filename= < ../clang-format-examples/test.cpp
Assertion failed: !HasError && "Cannot get value when an error exists!", file C:\llvm/llvm-project/llvm/include\llvm/Support/ErrorOr.h, line 243
Stack dump:
0.      Program arguments: C:\llvm\build\bin\clang-format.exe --assume-filename=
 #0 0x00007ff64d041b55 (C:\llvm\build\bin\clang-format.exe+0x41b55)
 #1 0x00007ff8efdcda2d (C:\WINDOWS\System32\ucrtbase.dll+0x6da2d)
 #2 0x00007ff8efdce901 (C:\WINDOWS\System32\ucrtbase.dll+0x6e901)
 #3 0x00007ff8efdd0261 (C:\WINDOWS\System32\ucrtbase.dll+0x70261)
 #4 0x00007ff8efdd0591 (C:\WINDOWS\System32\ucrtbase.dll+0x70591)
 #5 0x00007ff64d065cdd (C:\llvm\build\bin\clang-format.exe+0x65cdd)
 #6 0x00007ff64d0a11f3 (C:\llvm\build\bin\clang-format.exe+0xa11f3)
 #7 0x00007ff64d081dc3 (C:\llvm\build\bin\clang-format.exe+0x81dc3)
 #8 0x00007ff64d0817bb (C:\llvm\build\bin\clang-format.exe+0x817bb)
 #9 0x00007ff64d00b17c (C:\llvm\build\bin\clang-format.exe+0xb17c)
#10 0x00007ff64d00d515 (C:\llvm\build\bin\clang-format.exe+0xd515)
#11 0x00007ff64d12cc30 (C:\llvm\build\bin\clang-format.exe+0x12cc30)
#12 0x00007ff8efe77974 (C:\WINDOWS\System32\KERNEL32.DLL+0x17974)
#13 0x00007ff8f2caa271 (C:\WINDOWS\SYSTEM32\ntdll.dll+0x6a271)

[MyDeveloperDay]

@jr As there is no response from you, I wonder if you are ok with me taking this over, I'd like to recommend we keep just the:

if (AssumedFileName.empty()) {
    llvm::errs() << "error: empty filenames are not allowed\n";
    return true;
  }

For now, as the other functions where you are adding an assert might be being called from other tooling areas and I don't want to cause others problems, I'd like to keep this change localized, (I hope it's ok but I'll rebase and update the patch)

[MyDeveloperDay]

remove the asserts at least for now.

This fix is important for people using clang-format integrated into some editor tools.

[mitchell-stellar]

LGTM

lib/Basic/SourceManager.cpp

 }
 
 SourceManagerForFile::SourceManagerForFile(StringRef FileName,
                                            StringRef Content) {
   // This is referenced by `FileMgr` and will be released by `FileMgr` when it
   // is deleted.
   IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> InMemoryFileSystem(
       new llvm::vfs::InMemoryFileSystem);
-  InMemoryFileSystem->addFile(
+  bool DidAddFile = InMemoryFileSystem->addFile(
       FileName, 0,
       llvm::MemoryBuffer::getMemBuffer(Content, FileName,
                                        /*RequiresNullTerminator=*/false));
+  assert(DidAddFile && "Could not add file to InMemoryFileSystem");
   // This is passed to `SM` as reference, so the pointer has to be referenced
   // in `Environment` so that `FileMgr` can out-live this function scope.
   FileMgr =
       llvm::make_unique<FileManager>(FileSystemOptions(), InMemoryFileSystem);
   // This is passed to `SM` as reference, so the pointer has to be referenced
   // by `Environment` due to the same reason above.
   Diagnostics = llvm::make_unique<DiagnosticsEngine>(
       IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs),
       new DiagnosticOptions);
   SourceMgr = llvm::make_unique<SourceManager>(*Diagnostics, *FileMgr);
   FileID ID = SourceMgr->createFileID(FileMgr->getFile(FileName),
                                       SourceLocation(), clang::SrcMgr::C_User);
   assert(ID.isValid());
   SourceMgr->setMainFileID(ID);
 }

lib/Format/Format.cpp

bool isMpegTS(StringRef Code) {
   return Code.size() > 188 && Code[0] == 0x47 && Code[188] == 0x47;
 }
 
 bool isLikelyXml(StringRef Code) { return Code.ltrim().startswith("<"); }
 
 tooling::Replacements sortIncludes(const FormatStyle &Style, StringRef Code,
                                    ArrayRef<tooling::Range> Ranges,
                                    StringRef FileName, unsigned *Cursor) {
+  assert(!FileName.empty());
   tooling::Replacements Replaces;
   if (!Style.SortIncludes)
     return Replaces;
   if (isLikelyXml(Code))
     return Replaces;
   if (Style.Language == FormatStyle::LanguageKind::LK_JavaScript &&
       isMpegTS(Code))
     return Replaces;

 }
 
 namespace internal {
 std::pair<tooling::Replacements, unsigned>
 reformat(const FormatStyle &Style, StringRef Code,
          ArrayRef<tooling::Range> Ranges, unsigned FirstStartColumn,
          unsigned NextStartColumn, unsigned LastStartColumn, StringRef FileName,
          FormattingAttemptStatus *Status) {
+  assert(!FileName.empty());
   FormatStyle Expanded = expandPresets(Style);
   if (Expanded.DisableFormat)
     return {tooling::Replacements(), 0};
   if (isLikelyXml(Code))
     return {tooling::Replacements(), 0};
   if (Expanded.Language == FormatStyle::LK_JavaScript && isMpegTS(Code))
     return {tooling::Replacements(), 0};
 
return internal::reformat(Style, Code, Ranges,
                             /*NextStartColumn=*/0,
                             /*LastStartColumn=*/0, FileName, Status)
       .first;
 }
 
 tooling::Replacements cleanup(const FormatStyle &Style, StringRef Code,
                               ArrayRef<tooling::Range> Ranges,
                               StringRef FileName) {
+  assert(!FileName.empty());
   // cleanups only apply to C++ (they mostly concern ctor commas etc.)
   if (Style.Language != FormatStyle::LK_Cpp)
     return tooling::Replacements();
   return Cleaner(Environment(Code, FileName, Ranges), Style).process().first;
 }
 
 tooling::Replacements reformat(const FormatStyle &Style, StringRef Code,
                                ArrayRef<tooling::Range> Ranges,
                                StringRef FileName, bool *IncompleteFormat) {
   FormattingAttemptStatus Status;
   auto Result = reformat(Style, Code, Ranges, FileName, &Status);
   if (!Status.FormatComplete)
     *IncompleteFormat = true;
   return Result;
 }
 
 tooling::Replacements fixNamespaceEndComments(const FormatStyle &Style,
                                               StringRef Code,
                                               ArrayRef<tooling::Range> Ranges,
                                               StringRef FileName) {
+  assert(!FileName.empty());
   return NamespaceEndCommentsFixer(Environment(Code, FileName, Ranges), Style)
       .process()
       .first;
 }
 
 tooling::Replacements sortUsingDeclarations(const FormatStyle &Style,
                                             StringRef Code,
                                             ArrayRef<tooling::Range> Ranges,
                                             StringRef FileName) {
+  assert(!FileName.empty());
   return UsingDeclarationsSorter(Environment(Code, FileName, Ranges), Style)
       .process()
       .first;
 }
 
 LangOptions getFormattingLangOpts(const FormatStyle &Style) {
   LangOptions LangOpts;
   LangOpts.CPlusPlus = 1;

tools/clang-format/ClangFormat.cpp

static cl::list<std::string> FileNames(cl::Positional, cl::desc("[<file> ...]"),
                                        cl::cat(ClangFormatCategory));
 
 namespace clang {
 namespace format {
 
 static FileID createInMemoryFile(StringRef FileName, MemoryBuffer *Source,
                                  SourceManager &Sources, FileManager &Files,
                                  llvm::vfs::InMemoryFileSystem *MemFS) {
-  MemFS->addFileNoOwn(FileName, 0, Source);
+  bool DidAddFile = MemFS->addFileNoOwn(FileName, 0, Source);
+  assert(DidAddFile && "Could not add file to InMemoryFileSystem");
   return Sources.createFileID(Files.getFile(FileName), SourceLocation(),
                               SrcMgr::C_User);
 }
 
 // Parses <start line>:<end line> input to a pair of line numbers.
 // Returns true on error.
 static bool parseLineRange(StringRef Input, unsigned &FromLine,
                            unsigned &ToLine) {
static bool format(StringRef FileName) {
   }
   std::unique_ptr<llvm::MemoryBuffer> Code = std::move(CodeOrErr.get());
   if (Code->getBufferSize() == 0)
     return false; // Empty files are formatted correctly.
   std::vector<tooling::Range> Ranges;
   if (fillRanges(Code.get(), Ranges))
     return true;
   StringRef AssumedFileName = (FileName == "-") ? AssumeFileName : FileName;
+  if (AssumedFileName.empty()) {
+    llvm::errs() << "error: empty filenames are not allowed\n";
+    return true;
+  }
 
   llvm::Expected<FormatStyle> FormatStyle =
       getStyle(Style, AssumedFileName, FallbackStyle, Code->getBuffer());
   if (!FormatStyle) {
     llvm::errs() << llvm::toString(FormatStyle.takeError()) << "\n";
     return true;
   }