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

5 files changed, 118 insertions, 5 deletions

diff --git a/clang-tidy/.editorconfig b/clang-tidy/.editorconfig
new file mode 100644
index 000000000..19ee09eec
--- /dev/null
+++ b/clang-tidy/.editorconfig
@@ -0,0 +1,4 @@
+# LLVM style code is 2-space indented
+[*.{cc,hh}]
+indent_style = space
+indent_size = 2
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
diff --git a/clang-tidy/FixIncludes.hh b/clang-tidy/FixIncludes.hh
new file mode 100644
index 000000000..ea890cd39
--- /dev/null
+++ b/clang-tidy/FixIncludes.hh
@@ -0,0 +1,21 @@
+#pragma once
+///@file
+
+#include <clang-tidy/ClangTidyCheck.h>
+#include <clang/ASTMatchers/ASTMatchFinder.h>
+#include <llvm/ADT/StringRef.h>
+
+namespace nix::clang_tidy {
+
+using namespace clang;
+using namespace clang::tidy;
+
+class FixIncludesCheck : public ClangTidyCheck {
+    public:
+    FixIncludesCheck(StringRef Name, ClangTidyContext *Context)
+            : ClangTidyCheck(Name, Context) {}
+
+    void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) override;
+};
+
+};
diff --git a/clang-tidy/NixClangTidyChecks.cc b/clang-tidy/LixClangTidyChecks.cc
index 8f0309107..b3503dd3a 100644
--- a/clang-tidy/NixClangTidyChecks.cc
+++ b/clang-tidy/LixClangTidyChecks.cc
@@ -1,5 +1,6 @@
 #include <clang-tidy/ClangTidyModule.h>
 #include <clang-tidy/ClangTidyModuleRegistry.h>
+#include "FixIncludes.hh"
 #include "HasPrefixSuffix.hh"
 
 namespace nix::clang_tidy {
@@ -9,9 +10,10 @@ using namespace clang::tidy;
 class NixClangTidyChecks : public ClangTidyModule {
     public:
         void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
-            CheckFactories.registerCheck<HasPrefixSuffixCheck>("nix-hasprefixsuffix");
+            CheckFactories.registerCheck<HasPrefixSuffixCheck>("lix-hasprefixsuffix");
+            CheckFactories.registerCheck<FixIncludesCheck>("lix-fixincludes");
         }
 };
 
-static ClangTidyModuleRegistry::Add<NixClangTidyChecks> X("nix-module", "Adds nix specific checks");
+static ClangTidyModuleRegistry::Add<NixClangTidyChecks> X("lix-module", "Adds lix specific checks");
 };
diff --git a/clang-tidy/meson.build b/clang-tidy/meson.build
index 48770e39f..c59164a72 100644
--- a/clang-tidy/meson.build
+++ b/clang-tidy/meson.build
@@ -1,8 +1,13 @@
-project('nix-clang-tidy', ['cpp', 'c'],
+project('lix-clang-tidy', ['cpp', 'c'],
   version : '0.1',
   default_options : ['warning_level=3', 'cpp_std=c++20'])
 
 llvm = dependency('Clang', version: '>= 14', modules: ['libclang'])
-sources = ['HasPrefixSuffix.cc', 'NixClangTidyChecks.cc']
-shared_module('nix-clang-tidy', sources,
+sources = files(
+  'HasPrefixSuffix.cc',
+  'LixClangTidyChecks.cc',
+  'FixIncludes.cc',
+)
+
+shared_module('lix-clang-tidy', sources,
   dependencies: llvm)