Create clang-tidy check to rename all our includes

It is a little bit scuffed, but it seems to produce correct results. We
can run it at a later date when we want to explode every in-flight
commit in existence and then need to filter-branch them.

Fixes: https://git.lix.systems/lix-project/lix/issues/188

Change-Id: Id97e4651f78804a941d941df02c7c1b21ce453b6

1 files changed, 81 insertions, 0 deletions

diff --git a/clang-tidy/FixIncludes.cc b/clang-tidy/FixIncludes.cc
new file mode 100644
index 000000000..8ba350243
--- /dev/null
+++ b/clang-tidy/FixIncludes.cc
@@ -0,0 +1,81 @@
+#include "FixIncludes.hh"
+#include <clang-tidy/ClangTidyCheck.h>
+#include <clang/Basic/Diagnostic.h>
+#include <clang/Basic/SourceManager.h>
+#include <clang/Lex/PPCallbacks.h>
+#include <clang/Lex/Preprocessor.h>
+#include <llvm/ADT/StringRef.h>
+#include <llvm/Support/Debug.h>
+#include <memory>
+#include <set>
+#include <string>
+
+namespace nix::clang_tidy {
+
+using namespace clang;
+using namespace clang::tidy;
+
+class FixIncludesCallbacks : public PPCallbacks {
+public:
+  ClangTidyCheck &Check;
+  Preprocessor &PP;
+  FixIncludesCallbacks(ClangTidyCheck &Check, Preprocessor &PP)
+      : Check(Check), PP(PP) {}
+
+private:
+  bool Ignore = false;
+  virtual void LexedFileChanged(FileID FID, LexedFileChangeReason Reason,
+                                SrcMgr::CharacteristicKind FileType,
+                                FileID PrevFID, SourceLocation Loc) override;
+
+  virtual void InclusionDirective(SourceLocation HashLoc,
+                                  const Token &IncludeTok, StringRef FileName,
+                                  bool IsAngled, CharSourceRange FilenameRange,
+                                  OptionalFileEntryRef File,
+                                  StringRef SearchPath, StringRef RelativePath,
+                                  const Module *Imported,
+                                  SrcMgr::CharacteristicKind FileType) override;
+};
+
+void FixIncludesCallbacks::LexedFileChanged(FileID, LexedFileChangeReason,
+                                            SrcMgr::CharacteristicKind FileType,
+                                            FileID, SourceLocation) {
+  Ignore = FileType != SrcMgr::C_User;
+}
+
+void FixIncludesCallbacks::InclusionDirective(
+    SourceLocation, const Token &, StringRef, bool,
+    CharSourceRange FilenameRange, OptionalFileEntryRef File, StringRef,
+    StringRef, const Module *, SrcMgr::CharacteristicKind) {
+  if (Ignore)
+    return;
+
+  // FIXME: this is kinda evil, but this is a one-time fixup
+  const std::string SourceDir = "src/";
+
+  if (File && File->getNameAsRequested().contains(SourceDir)) {
+    StringRef Name = File->getNameAsRequested();
+    auto Idx = Name.find(SourceDir);
+    assert(Idx != std::string::npos);
+    StringRef Suffix = Name.drop_front(Idx + SourceDir.length());
+
+    if (!Suffix.starts_with("lib")) {
+      llvm::dbgs() << "ignored: " << Suffix << "\n";
+      return;
+    }
+
+    auto Diag = Check.diag(FilenameRange.getBegin(),
+                           "include needs to specify the source subdir");
+
+    Diag << FilenameRange
+         << FixItHint::CreateReplacement(FilenameRange,
+                                         ("\"" + Suffix + "\"").str());
+  }
+}
+
+void FixIncludesCheck::registerPPCallbacks(const SourceManager &,
+                                           Preprocessor *PP, Preprocessor *) {
+  PP->addPPCallbacks(std::make_unique<FixIncludesCallbacks>(*this, *PP));
+}
+
+}; // namespace nix::clang_tidy