[ASTImporter] Add an ImportImpl method to allow customizing Import behavior.

Summary:
We are currently implementing support in LLDB that reconstructs the STL templates from
the target program in the expression evaluator. This reconstruction happens during the
import process from our debug info AST into the expression evaluation AST, which means
we need a way to intercept the ASTImporter import process.

This patch adds an protected ImportImpl method that we can overwrite in LLDB to implement
our special importing logic (which is essentially just looking into a C++ module that is attached to
the target context). Because ImportImpl has to call MapImported/AddToLookup for the decls it
creates, this patch also exposes those via a new unified method and checks that we call it when
importing decls.

Reviewers: martong, balazske, a.sidorin, shafik, a_sidorin

Reviewed By: martong, a_sidorin

Subscribers: rnkovacs, cfe-commits, lldb-commits, aprantl

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59485

llvm-svn: 359502

1 files changed, 101 insertions, 9 deletions

diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
index 48d479d8af2..07a7c3aea81 100644
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -313,6 +313,17 @@ class ASTImporterTestBase : public CompilerOptionSpecificTest {
   const char *const InputFileName = "input.cc";
   const char *const OutputFileName = "output.cc";
 
+public:
+  /// Allocates an ASTImporter (or one of its subclasses).
+  typedef std::function<ASTImporter *(ASTContext &, FileManager &, ASTContext &,
+                                      FileManager &, bool,
+                                      ASTImporterLookupTable *)>
+      ImporterConstructor;
+
+  // The lambda that constructs the ASTImporter we use in this test.
+  ImporterConstructor Creator;
+
+private:
   // Buffer for the To context, must live in the test scope.
   std::string ToCode;
 
@@ -325,22 +336,32 @@ class ASTImporterTestBase : public CompilerOptionSpecificTest {
     std::unique_ptr<ASTUnit> Unit;
     TranslationUnitDecl *TUDecl = nullptr;
     std::unique_ptr<ASTImporter> Importer;
-    TU(StringRef Code, StringRef FileName, ArgVector Args)
+    ImporterConstructor Creator;
+    TU(StringRef Code, StringRef FileName, ArgVector Args,
+       ImporterConstructor C = ImporterConstructor())
         : Code(Code), FileName(FileName),
           Unit(tooling::buildASTFromCodeWithArgs(this->Code, Args,
                                                  this->FileName)),
-          TUDecl(Unit->getASTContext().getTranslationUnitDecl()) {
+          TUDecl(Unit->getASTContext().getTranslationUnitDecl()), Creator(C) {
       Unit->enableSourceFileDiagnostics();
+
+      // If the test doesn't need a specific ASTImporter, we just create a
+      // normal ASTImporter with it.
+      if (!Creator)
+        Creator = [](ASTContext &ToContext, FileManager &ToFileManager,
+                     ASTContext &FromContext, FileManager &FromFileManager,
+                     bool MinimalImport, ASTImporterLookupTable *LookupTable) {
+          return new ASTImporter(ToContext, ToFileManager, FromContext,
+                                 FromFileManager, MinimalImport, LookupTable);
+        };
     }
 
     void lazyInitImporter(ASTImporterLookupTable &LookupTable, ASTUnit *ToAST) {
       assert(ToAST);
-      if (!Importer) {
-        Importer.reset(
-            new ASTImporter(ToAST->getASTContext(), ToAST->getFileManager(),
-                            Unit->getASTContext(), Unit->getFileManager(),
-                            false, &LookupTable));
-      }
+      if (!Importer)
+        Importer.reset(Creator(ToAST->getASTContext(), ToAST->getFileManager(),
+                               Unit->getASTContext(), Unit->getFileManager(),
+                               false, &LookupTable));
       assert(&ToAST->getASTContext() == &Importer->getToContext());
       createVirtualFileIfNeeded(ToAST, FileName, Code);
     }
@@ -424,7 +445,7 @@ public:
     ArgVector FromArgs = getArgVectorForLanguage(FromLang),
               ToArgs = getArgVectorForLanguage(ToLang);
 
-    FromTUs.emplace_back(FromSrcCode, InputFileName, FromArgs);
+    FromTUs.emplace_back(FromSrcCode, InputFileName, FromArgs, Creator);
     TU &FromTU = FromTUs.back();
 
     assert(!ToAST);
@@ -562,6 +583,74 @@ TEST_P(CanonicalRedeclChain, ShouldBeSameForAllDeclInTheChain) {
   EXPECT_THAT(RedeclsD1, ::testing::ContainerEq(RedeclsD2));
 }
 
+namespace {
+struct RedirectingImporter : public ASTImporter {
+  using ASTImporter::ASTImporter;
+
+protected:
+  llvm::Expected<Decl *> ImportImpl(Decl *FromD) override {
+    auto *ND = dyn_cast<NamedDecl>(FromD);
+    if (!ND || ND->getName() != "shouldNotBeImported")
+      return ASTImporter::ImportImpl(FromD);
+    for (Decl *D : getToContext().getTranslationUnitDecl()->decls()) {
+      if (auto *ND = dyn_cast<NamedDecl>(D))
+        if (ND->getName() == "realDecl") {
+          RegisterImportedDecl(FromD, ND);
+          return ND;
+        }
+    }
+    return ASTImporter::ImportImpl(FromD);
+  }
+};
+
+} // namespace
+
+struct RedirectingImporterTest : ASTImporterOptionSpecificTestBase {
+  RedirectingImporterTest() {
+    Creator = [](ASTContext &ToContext, FileManager &ToFileManager,
+                 ASTContext &FromContext, FileManager &FromFileManager,
+                 bool MinimalImport, ASTImporterLookupTable *LookupTable) {
+      return new RedirectingImporter(ToContext, ToFileManager, FromContext,
+                                     FromFileManager, MinimalImport,
+                                     LookupTable);
+    };
+  }
+};
+
+// Test that an ASTImporter subclass can intercept an import call.
+TEST_P(RedirectingImporterTest, InterceptImport) {
+  Decl *From, *To;
+  std::tie(From, To) =
+      getImportedDecl("class shouldNotBeImported {};", Lang_CXX,
+                      "class realDecl {};", Lang_CXX, "shouldNotBeImported");
+  auto *Imported = cast<CXXRecordDecl>(To);
+  EXPECT_EQ(Imported->getQualifiedNameAsString(), "realDecl");
+
+  // Make sure our importer prevented the importing of the decl.
+  auto *ToTU = Imported->getTranslationUnitDecl();
+  auto Pattern = functionDecl(hasName("shouldNotBeImported"));
+  unsigned count =
+      DeclCounterWithPredicate<CXXRecordDecl>().match(ToTU, Pattern);
+  EXPECT_EQ(0U, count);
+}
+
+// Test that when we indirectly import a declaration the custom ASTImporter
+// is still intercepting the import.
+TEST_P(RedirectingImporterTest, InterceptIndirectImport) {
+  Decl *From, *To;
+  std::tie(From, To) =
+      getImportedDecl("class shouldNotBeImported {};"
+                      "class F { shouldNotBeImported f; };",
+                      Lang_CXX, "class realDecl {};", Lang_CXX, "F");
+
+  // Make sure our ASTImporter prevented the importing of the decl.
+  auto *ToTU = To->getTranslationUnitDecl();
+  auto Pattern = functionDecl(hasName("shouldNotBeImported"));
+  unsigned count =
+      DeclCounterWithPredicate<CXXRecordDecl>().match(ToTU, Pattern);
+  EXPECT_EQ(0U, count);
+}
+
 TEST_P(ImportExpr, ImportStringLiteral) {
   MatchVerifier<Decl> Verifier;
   testImport(
@@ -5549,6 +5638,9 @@ INSTANTIATE_TEST_CASE_P(ParameterizedTests, ImportDecl,
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ASTImporterOptionSpecificTestBase,
                         DefaultTestValuesForRunOptions, );
 
+INSTANTIATE_TEST_CASE_P(ParameterizedTests, RedirectingImporterTest,
+                        DefaultTestValuesForRunOptions, );
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ImportFunctions,
                         DefaultTestValuesForRunOptions, );