[libTooling] Generalize string explanation as templated metadata

Change RewriteRule from holding an `Explanation` to being able to generate
arbitrary metadata. Where TransformerClangTidyCheck was interested in a string
description for the diagnostic, other tools may be interested in richer metadata
at a higher level of abstraction than at the edit level (which is currently
available as ASTEdit::Metadata).

Reviewed By: ymandel

Differential Revision: https://reviews.llvm.org/D120360

1 files changed, 77 insertions, 9 deletions

diff --git a/clang/unittests/Tooling/TransformerTest.cpp b/clang/unittests/Tooling/TransformerTest.cpp
index 4ab3984..75ba9b9 100644
--- a/clang/unittests/Tooling/TransformerTest.cpp
+++ b/clang/unittests/Tooling/TransformerTest.cpp
@@ -31,9 +31,11 @@ using ::clang::transformer::makeRule;
 using ::clang::transformer::member;
 using ::clang::transformer::name;
 using ::clang::transformer::node;
+using ::clang::transformer::noEdits;
 using ::clang::transformer::remove;
 using ::clang::transformer::rewriteDescendants;
 using ::clang::transformer::RewriteRule;
+using ::clang::transformer::RewriteRuleWith;
 using ::clang::transformer::statement;
 using ::testing::ElementsAre;
 using ::testing::IsEmpty;
@@ -129,7 +131,7 @@ protected:
         Changes.insert(Changes.end(), std::make_move_iterator(C->begin()),
                        std::make_move_iterator(C->end()));
       } else {
-        // FIXME: stash this error rather then printing.
+        // FIXME: stash this error rather than printing.
         llvm::errs() << "Error generating changes: "
                      << llvm::toString(C.takeError()) << "\n";
         ++ErrorCount;
@@ -137,27 +139,58 @@ protected:
     };
   }
 
-  template <typename R>
-  void testRule(R Rule, StringRef Input, StringRef Expected) {
+  auto consumerWithStringMetadata() {
+    return [this](Expected<TransformerResult<std::string>> C) {
+      if (C) {
+        Changes.insert(Changes.end(),
+                       std::make_move_iterator(C->Changes.begin()),
+                       std::make_move_iterator(C->Changes.end()));
+        StringMetadata.push_back(std::move(C->Metadata));
+      } else {
+        // FIXME: stash this error rather than printing.
+        llvm::errs() << "Error generating changes: "
+                     << llvm::toString(C.takeError()) << "\n";
+        ++ErrorCount;
+      }
+    };
+  }
+
+  void testRule(RewriteRule Rule, StringRef Input, StringRef Expected) {
     Transformers.push_back(
         std::make_unique<Transformer>(std::move(Rule), consumer()));
     Transformers.back()->registerMatchers(&MatchFinder);
     compareSnippets(Expected, rewrite(Input));
   }
 
-  template <typename R> void testRuleFailure(R Rule, StringRef Input) {
+  void testRule(RewriteRuleWith<std::string> Rule, StringRef Input,
+                StringRef Expected) {
+    Transformers.push_back(std::make_unique<Transformer>(
+        std::move(Rule), consumerWithStringMetadata()));
+    Transformers.back()->registerMatchers(&MatchFinder);
+    compareSnippets(Expected, rewrite(Input));
+  }
+
+  void testRuleFailure(RewriteRule Rule, StringRef Input) {
     Transformers.push_back(
         std::make_unique<Transformer>(std::move(Rule), consumer()));
     Transformers.back()->registerMatchers(&MatchFinder);
     ASSERT_FALSE(rewrite(Input)) << "Expected failure to rewrite code";
   }
 
+  void testRuleFailure(RewriteRuleWith<std::string> Rule, StringRef Input) {
+    Transformers.push_back(std::make_unique<Transformer>(
+        std::move(Rule), consumerWithStringMetadata()));
+    Transformers.back()->registerMatchers(&MatchFinder);
+    ASSERT_FALSE(rewrite(Input)) << "Expected failure to rewrite code";
+  }
+
   // Transformers are referenced by MatchFinder.
   std::vector<std::unique_ptr<Transformer>> Transformers;
   clang::ast_matchers::MatchFinder MatchFinder;
   // Records whether any errors occurred in individual changes.
   int ErrorCount = 0;
   AtomicChanges Changes;
+  std::vector<std::string> StringMetadata;
 
 private:
   FileContentMappings FileContents = {{"header.h", ""}};
@@ -169,7 +202,7 @@ protected:
 };
 
 // Given string s, change strlen($s.c_str()) to REPLACED.
-static RewriteRule ruleStrlenSize() {
+static RewriteRuleWith<std::string> ruleStrlenSize() {
   StringRef StringExpr = "strexpr";
   auto StringType = namedDecl(hasAnyName("::basic_string", "::string"));
   auto R = makeRule(
@@ -886,12 +919,12 @@ TEST_F(TransformerTest, FlattenWithMixedArgs) {
 
 TEST_F(TransformerTest, OrderedRuleUnrelated) {
   StringRef Flag = "flag";
-  RewriteRule FlagRule = makeRule(
+  RewriteRuleWith<std::string> FlagRule = makeRule(
       cxxMemberCallExpr(on(expr(hasType(cxxRecordDecl(
                                     hasName("proto::ProtoCommandLineFlag"))))
                                .bind(Flag)),
                         unless(callee(cxxMethodDecl(hasName("GetProto"))))),
-      changeTo(node(std::string(Flag)), cat("PROTO")));
+      changeTo(node(std::string(Flag)), cat("PROTO")), cat(""));
 
   std::string Input = R"cc(
     proto::ProtoCommandLineFlag flag;
@@ -1657,8 +1690,8 @@ TEST_F(TransformerTest, MultiFileEdit) {
       makeRule(callExpr(callee(functionDecl(hasName("Func"))),
                         forEachArgumentWithParam(expr().bind("arg"),
                                                  parmVarDecl().bind("param"))),
-               editList({changeTo(node("arg"), cat("ARG")),
-                         changeTo(node("param"), cat("PARAM"))})),
+               {changeTo(node("arg"), cat("ARG")),
+                changeTo(node("param"), cat("PARAM"))}),
       [&](Expected<MutableArrayRef<AtomicChange>> Changes) {
         if (Changes)
           ChangeSets.push_back(AtomicChanges(Changes->begin(), Changes->end()));
@@ -1682,4 +1715,39 @@ TEST_F(TransformerTest, MultiFileEdit) {
                    "./input.h"))));
 }
 
+TEST_F(TransformerTest, GeneratesMetadata) {
+  std::string Input = R"cc(int target = 0;)cc";
+  std::string Expected = R"cc(REPLACE)cc";
+  RewriteRuleWith<std::string> Rule = makeRule(
+      varDecl(hasName("target")), changeTo(cat("REPLACE")), cat("METADATA"));
+  testRule(std::move(Rule), Input, Expected);
+  EXPECT_EQ(ErrorCount, 0);
+  EXPECT_THAT(StringMetadata, UnorderedElementsAre("METADATA"));
+}
+
+TEST_F(TransformerTest, GeneratesMetadataWithNoEdits) {
+  std::string Input = R"cc(int target = 0;)cc";
+  RewriteRuleWith<std::string> Rule = makeRule(
+      varDecl(hasName("target")).bind("var"), noEdits(), cat("METADATA"));
+  testRule(std::move(Rule), Input, Input);
+  EXPECT_EQ(ErrorCount, 0);
+  EXPECT_THAT(StringMetadata, UnorderedElementsAre("METADATA"));
+}
+
+TEST_F(TransformerTest, PropagateMetadataErrors) {
+  class AlwaysFail : public transformer::MatchComputation<std::string> {
+    llvm::Error eval(const ast_matchers::MatchFinder::MatchResult &,
+                     std::string *) const override {
+      return llvm::createStringError(llvm::errc::invalid_argument, "ERROR");
+    }
+    std::string toString() const override { return "AlwaysFail"; }
+  };
+  std::string Input = R"cc(int target = 0;)cc";
+  RewriteRuleWith<std::string> Rule = makeRule<std::string>(
+      varDecl(hasName("target")).bind("var"), changeTo(cat("REPLACE")),
+      std::make_shared<AlwaysFail>());
+  testRuleFailure(std::move(Rule), Input);
+  EXPECT_EQ(ErrorCount, 1);
+}
+
 } // namespace