[IncludeTree] Fix PPCallback for include tree that can cause missing .d file

For IncludeDirective callback from include-tree, do not callback with
null FileEntry as that dependency collector using that to indicate a
missing header include, and will not emit dependency file in this case.

Unlike a regular callback from Lexer, include tree doesn't resolve
headers so it cannot callback with a FileEntry to the header file being
included when the include is actually a module. The behavior for the
callback has to be changed slightly that it uses the ASTFile FileEntry.

rdar://126885995

Author: cachemeifyoucan

clang/lib/Lex/PPDirectives.cpp

@@ -2015,11 +2015,10 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
       SrcMgr::CharacteristicKind FileCharacter =
           SourceMgr.getFileCharacteristic(FilenameTok.getLocation());
       if (SuggestedModule)
-        Callbacks->InclusionDirective(HashLoc, IncludeTok, Filename, isAngled,
-                                      FilenameRange, OptionalFileEntryRef(),
-                                      /*SearchPath=*/"", /*RelativePath=*/"",
-                                      SuggestedModule,
-                                      /*ModuleImported=*/true, FileCharacter);
+        Callbacks->InclusionDirective(
+            HashLoc, IncludeTok, Filename, isAngled, FilenameRange, FileRef,
+            /*SearchPath=*/"", /*RelativePath=*/"", SuggestedModule,
+            /*ModuleImported=*/true, FileCharacter);
       else
         Callbacks->InclusionDirective(
             HashLoc, IncludeTok, Filename, isAngled, FilenameRange, FileRef,
@@ -2101,7 +2100,14 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
           return;
       }
 
-      InclusionCallback({}, Imported);
+      // PPCallback for IncludeDirective. Using the AST file as the FileEntry in
+      // the callback to indicate this is not a missing header. Note this is not
+      // the same behavior as non-include-tree build where the FileEntry is for
+      // the header file.
+      // FIXME: Need to clarify what `File` means in the callback, and if that
+      // can be the module file entry instead of header file entry.
+      Module *M = Imported;
+      InclusionCallback(M->getASTFile(), Imported);
       makeModuleVisible(Imported, EndLoc);
       if (IncludeTok.getIdentifierInfo()->getPPKeywordID() !=
           tok::pp___include_macros)

clang/test/ClangScanDeps/modules-include-tree-dependency-file.c

@@ -0,0 +1,62 @@
+// REQUIRES: ondisk_cas
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed "s|DIR|%/t|g" %t/cdb.json.template > %t/cdb.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb.json \
+// RUN:   -cas-path %t/cas -format experimental-include-tree-full > %t/deps.json
+
+// RUN: %deps-to-rsp %t/deps.json --module-name Mod_Private > %t/private.rsp
+// RUN: %deps-to-rsp %t/deps.json --module-name Mod > %t/mod.rsp
+// RUN: %deps-to-rsp %t/deps.json --tu-index 0 > %t/tu.rsp
+// RUN: %clang @%t/private.rsp
+// RUN: %clang @%t/mod.rsp
+// RUN: %clang @%t/tu.rsp -dependency-dot %t/tu.dot
+/// Check dependency file is generated.
+// RUN: find %t/module-cache -name "*.d" | wc -l | grep 2
+// RUN: FileCheck %s -input-file=%t/tu.d
+
+// CHECK: dependencies:
+// CHECK-DAG: tu.m
+// CHECK-DAG: A.h
+
+// RUN: FileCheck %s -input-file=%t/tu.dot -check-prefix DOT
+// DOT: digraph "dependencies"
+// DOT-DAG: [[TU:header_[0-9]+]] [ shape="box", label="{{.*}}{{/|\\}}tu.m"];
+// DOT-DAG: [[HEADER:header_[0-9]+]] [ shape="box", label="{{.*}}{{/|\\}}A.h"];
+// DOT-DAG: [[PCM:header_[0-9]+]] [ shape="box", label="{{.*}}{{/|\\}}Mod-{{.*}}.pcm"];
+// DOT-DAG: [[TU]] -> [[HEADER]]
+// DOT-DAG: [[HEADER]] -> [[PCM]]
+
+//--- cdb.json.template
+[{
+  "file": "DIR/tu.m",
+  "directory": "DIR",
+  "command": "clang -fsyntax-only DIR/tu.m -F DIR -I DIR -fmodule-name=A -fmodules -fimplicit-modules -fimplicit-module-maps -fmodules-cache-path=DIR/module-cache -MMD -MT dependencies -MF DIR/tu.d"
+}]
+
+//--- Mod.framework/Modules/module.modulemap
+framework module Mod { header "Mod.h" }
+
+//--- Mod.framework/Modules/module.private.modulemap
+framework module Mod_Private { header "Priv.h" }
+
+//--- module.modulemap
+module A {
+  header "A.h"
+  export *
+}
+
+//--- A.h
+#include <Mod/Mod.h>
+
+//--- Mod.framework/Headers/Mod.h
+#include <Mod/Priv.h>
+void pub(void);
+
+//--- Mod.framework/PrivateHeaders/Priv.h
+void priv(void);
+
+//--- tu.m
+#import "A.h"