[clang][cas] Fix include-tree with pch importing public/private modules

We were dropping the modular import of a private module if its public
module was imported via PCH, because we skipped parsing the private
modulemap during scanning.

(cherry picked from commit 6034ccd)

Author: benlangmuir

clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp

@@ -154,6 +154,19 @@ struct PPCallbacksDependencyCollector : public DependencyCollector {
     PP.addPPCallbacks(std::move(CB));
   }
 };
+/// A utility for adding \c ASTReaderListener to a compiler instance at the
+/// appropriate time.
+struct ASTReaderListenerDependencyCollector : public DependencyCollector {
+  using MakeL =
+      llvm::unique_function<std::unique_ptr<ASTReaderListener>(ASTReader &R)>;
+  MakeL Create;
+  ASTReaderListenerDependencyCollector(MakeL Create) : Create(std::move(Create)) {}
+  void attachToASTReader(ASTReader &R) final {
+    std::unique_ptr<ASTReaderListener> L = Create(R);
+    assert(L);
+    R.addListener(std::move(L));
+  }
+};
 
 struct IncludeTreePPCallbacks : public PPCallbacks {
   IncludeTreeBuilder &Builder;
@@ -218,6 +231,40 @@ struct IncludeTreePPCallbacks : public PPCallbacks {
     Builder.exitedSubmodule(PP, M, ImportLoc, ForPragma);
   }
 };
+
+/// Utility to trigger module lookup in header search for modules loaded via
+/// PCH. This causes dependency scanning via PCH to parse modulemap files at
+/// roughly the same point they would with modulemap files embedded in the pcms,
+/// which is disabled with include-tree modules. Without this, we can fail to
+/// find modules that are in the same directory as a named import, since
+/// it may be skipped during search (see \c loadFrameworkModule).
+///
+/// The specific lookup we do matches what happens in ASTReader for the
+/// MODULE_DIRECTORY record, and ignores the result.
+class LookupPCHModulesListener : public ASTReaderListener {
+public:
+  LookupPCHModulesListener(Preprocessor &PP) : PP(PP) {}
+
+private:
+  void ReadModuleName(StringRef ModuleName) final {
+    if (PCHFinished)
+      return;
+    // Match MODULE_DIRECTORY: allow full search and ignore failure to find
+    // the module.
+    (void)PP.getHeaderSearchInfo().lookupModule(
+        ModuleName, SourceLocation(), /*AllowSearch=*/true,
+        /*AllowExtraModuleMapSearch=*/true);
+  }
+  void visitModuleFile(StringRef Filename,
+                       serialization::ModuleKind Kind) final {
+    if (Kind == serialization::MK_PCH)
+      PCHFinished = true;
+  }
+
+private:
+  Preprocessor &PP;
+  bool PCHFinished = false;
+};
 } // namespace
 
 /// The PCH recorded file paths with canonical paths, create a VFS that
@@ -275,6 +322,15 @@ Error IncludeTreeActionController::initialize(
       });
   ScanInstance.addDependencyCollector(std::move(DC));
 
+  // Attach callback for modules loaded via PCH.
+  if (!ScanInstance.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
+    auto DC = std::make_shared<ASTReaderListenerDependencyCollector>(
+      [&](ASTReader &R) {
+        return std::make_unique<LookupPCHModulesListener>(R.getPreprocessor());
+      });
+    ScanInstance.addDependencyCollector(std::move(DC));
+  }
+
   // Enable caching in the resulting commands.
   ScanInstance.getFrontendOpts().CacheCompileJob = true;
   CASOpts = ScanInstance.getCASOpts();

clang/test/ClangScanDeps/modules-include-tree-pch-with-private.c

@@ -0,0 +1,65 @@
+// Test importing a private module whose public module was previously imported
+// via a PCH.
+
+// 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: sed "s|DIR|%/t|g" %t/cdb_pch.json.template > %t/cdb_pch.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb_pch.json \
+// RUN:   -cas-path %t/cas -module-files-dir %t/outputs \
+// RUN:   -format experimental-include-tree-full -mode preprocess-dependency-directives \
+// RUN:   > %t/deps_pch.json
+
+// RUN: %deps-to-rsp %t/deps_pch.json --module-name Mod > %t/Mod.rsp
+// RUN: %deps-to-rsp %t/deps_pch.json --tu-index 0 > %t/pch.rsp
+// RUN: %clang @%t/Mod.rsp
+// RUN: %clang @%t/pch.rsp
+
+// RUN: clang-scan-deps -compilation-database %t/cdb.json \
+// RUN:   -cas-path %t/cas -module-files-dir %t/outputs \
+// RUN:   -format experimental-include-tree-full -mode preprocess-dependency-directives \
+// RUN:   > %t/deps.json
+
+// RUN: %deps-to-rsp %t/deps.json --module-name Mod_Private > %t/Mod_Private.rsp
+// RUN: %deps-to-rsp %t/deps.json --tu-index 0 > %t/tu.rsp
+// RUN: %clang @%t/Mod_Private.rsp
+// RUN: %clang @%t/tu.rsp
+
+//--- cdb.json.template
+[{
+  "file": "DIR/tu.m",
+  "directory": "DIR",
+  "command": "clang -fsyntax-only DIR/tu.m -include prefix.h -F DIR -fmodules -fimplicit-modules -fimplicit-module-maps -fmodules-cache-path=DIR/module-cache"
+}]
+
+//--- cdb_pch.json.template
+[{
+  "file": "DIR/prefix.h",
+  "directory": "DIR",
+  "command": "clang -x objective-c-header DIR/prefix.h -o DIR/prefix.h.pch -F DIR -fmodules -fimplicit-modules -fimplicit-module-maps -fmodules-cache-path=DIR/module-cache"
+}]
+
+//--- Mod.framework/Modules/module.modulemap
+framework module Mod { header "Mod.h" }
+
+//--- Mod.framework/Modules/module.private.modulemap
+framework module Mod_Private { header "Priv.h" }
+
+//--- Mod.framework/Headers/Mod.h
+void pub(void);
+
+//--- Mod.framework/PrivateHeaders/Priv.h
+void priv(void);
+
+//--- prefix.h
+#import <Mod/Mod.h>
+
+//--- tu.m
+#import <Mod/Priv.h>
+void tu(void) {
+  pub();
+  priv();
+}