[Lex] Introduce `PPCallbacks::LexedFileChanged()` preprocessor callback

This is a preprocessor callback focused on the lexed file changing, without conflating effects of line number directives and other pragmas.
A client that only cares about what files the lexer processes, like dependency generation, can use this more straightforward
callback instead of `PPCallbacks::FileChanged()`. Clients that want the pragma directive effects as well can keep using `FileChanged()`.

A use case where `PPCallbacks::LexedFileChanged()` is particularly simpler to use than `FileChanged()` is in a situation
where a client wants to keep track of lexed file changes that include changes from/to the predefines buffer, where it becomes
unnecessary complicated trying to use `FileChanged()` while filtering out the pragma directives effects callbacks.

Also take the opportunity to provide information about the prior `FileID` the `Lexer` moved from, even when entering a new file.

Differential Revision: https://reviews.llvm.org/D128947

1 files changed, 14 insertions, 15 deletions

diff --git a/clang/lib/Frontend/DependencyFile.cpp b/clang/lib/Frontend/DependencyFile.cpp
index 3a810e5..06ddb0f 100644
--- a/clang/lib/Frontend/DependencyFile.cpp
+++ b/clang/lib/Frontend/DependencyFile.cpp
@@ -31,23 +31,21 @@ using namespace clang;
 namespace {
 struct DepCollectorPPCallbacks : public PPCallbacks {
   DependencyCollector &DepCollector;
-  SourceManager &SM;
-  DiagnosticsEngine &Diags;
-  DepCollectorPPCallbacks(DependencyCollector &L, SourceManager &SM,
-                          DiagnosticsEngine &Diags)
-      : DepCollector(L), SM(SM), Diags(Diags) {}
-
-  void FileChanged(SourceLocation Loc, FileChangeReason Reason,
-                   SrcMgr::CharacteristicKind FileType,
-                   FileID PrevFID) override {
-    if (Reason != PPCallbacks::EnterFile)
+  Preprocessor &PP;
+  DepCollectorPPCallbacks(DependencyCollector &L, Preprocessor &PP)
+      : DepCollector(L), PP(PP) {}
+
+  void LexedFileChanged(FileID FID, LexedFileChangeReason Reason,
+                        SrcMgr::CharacteristicKind FileType, FileID PrevFID,
+                        SourceLocation Loc) override {
+    if (Reason != PPCallbacks::LexedFileChangeReason::EnterFile)
       return;
 
     // Dependency generation really does want to go all the way to the
     // file entry for a source location to find out what is depended on.
     // We do not want #line markers to affect dependency generation!
-    if (Optional<StringRef> Filename = SM.getNonBuiltinFilenameForID(
-            SM.getFileID(SM.getExpansionLoc(Loc))))
+    if (Optional<StringRef> Filename =
+            PP.getSourceManager().getNonBuiltinFilenameForID(FID))
       DepCollector.maybeAddDependency(
           llvm::sys::path::remove_leading_dotslash(*Filename),
           /*FromModule*/ false, isSystem(FileType), /*IsModuleFile*/ false,
@@ -90,7 +88,9 @@ struct DepCollectorPPCallbacks : public PPCallbacks {
                                     /*IsMissing=*/false);
   }
 
-  void EndOfMainFile() override { DepCollector.finishedMainFile(Diags); }
+  void EndOfMainFile() override {
+    DepCollector.finishedMainFile(PP.getDiagnostics());
+  }
 };
 
 struct DepCollectorMMCallbacks : public ModuleMapCallbacks {
@@ -175,8 +175,7 @@ bool DependencyCollector::sawDependency(StringRef Filename, bool FromModule,
 
 DependencyCollector::~DependencyCollector() { }
 void DependencyCollector::attachToPreprocessor(Preprocessor &PP) {
-  PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(
-      *this, PP.getSourceManager(), PP.getDiagnostics()));
+  PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(*this, PP));
   PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
       std::make_unique<DepCollectorMMCallbacks>(*this));
 }