[clang-tidy] Generalize TransformerClangTidyCheck to take a rule generator.

Summary: Tidy check behavior often depends on language and/or clang-tidy options. This revision allows a user of TranformerClangTidyCheck to pass rule _generator_ in place of a rule, where the generator takes both the language and clang-tidy options. Additionally, the generator returns an `Optional` to allow for the case where the check is deemed irrelevant/disable based on those options.

Reviewers: gribozavr

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63288

llvm-svn: 364442

3 files changed, 105 insertions, 15 deletions

diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
index 80a82980868..1dedb0571c3 100644
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
@@ -14,20 +14,40 @@ namespace tidy {
 namespace utils {
 using tooling::RewriteRule;
 
+static bool hasExplanation(const RewriteRule::Case &C) {
+  return C.Explanation != nullptr;
+}
+
+// This constructor cannot dispatch to the simpler one (below), because, in
+// order to get meaningful results from `getLangOpts` and `Options`, we need the
+// `ClangTidyCheck()` constructor to have been called. If we were to dispatch,
+// we would be accessing `getLangOpts` and `Options` before the underlying
+// `ClangTidyCheck` instance was properly initialized.
+TransformerClangTidyCheck::TransformerClangTidyCheck(
+    std::function<Optional<RewriteRule>(const LangOptions &,
+                                        const OptionsView &)>
+        MakeRule,
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context), Rule(MakeRule(getLangOpts(), Options)) {
+  if (Rule)
+    assert(llvm::all_of(Rule->Cases, hasExplanation) &&
+           "clang-tidy checks must have an explanation by default;"
+           " explicitly provide an empty explanation if none is desired");
+}
+
 TransformerClangTidyCheck::TransformerClangTidyCheck(RewriteRule R,
                                                      StringRef Name,
                                                      ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context), Rule(std::move(R)) {
-  assert(llvm::all_of(Rule.Cases, [](const RewriteRule::Case &C) {
-                       return C.Explanation != nullptr;
-                     }) &&
+  assert(llvm::all_of(Rule->Cases, hasExplanation) &&
          "clang-tidy checks must have an explanation by default;"
          " explicitly provide an empty explanation if none is desired");
 }
 
 void TransformerClangTidyCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
-  Finder->addDynamicMatcher(tooling::detail::buildMatcher(Rule), this);
+  if (Rule)
+    Finder->addDynamicMatcher(tooling::detail::buildMatcher(*Rule), this);
 }
 
 void TransformerClangTidyCheck::check(
@@ -43,7 +63,8 @@ void TransformerClangTidyCheck::check(
       Root->second.getSourceRange().getBegin());
   assert(RootLoc.isValid() && "Invalid location for Root node of match.");
 
-  RewriteRule::Case Case = tooling::detail::findSelectedCase(Result, Rule);
+  assert(Rule && "check() should not fire if Rule is None");
+  RewriteRule::Case Case = tooling::detail::findSelectedCase(Result, *Rule);
   Expected<SmallVector<tooling::detail::Transformation, 1>> Transformations =
       tooling::detail::translateEdits(Result, Case.Edits);
   if (!Transformations) {
diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
index faf946ceb0f..0cd386f5b07 100644
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
@@ -31,19 +31,32 @@ namespace utils {
 // };
 class TransformerClangTidyCheck : public ClangTidyCheck {
 public:
-  // All cases in \p R must have a non-null \c Explanation, even though \c
-  // Explanation is optional for RewriteRule in general. Because the primary
-  // purpose of clang-tidy checks is to provide users with diagnostics, we
-  // assume that a missing explanation is a bug.  If no explanation is desired,
-  // indicate that explicitly (for example, by passing `text("no explanation")`
-  //  to `makeRule` as the `Explanation` argument).
+  // \p MakeRule generates the rewrite rule to be used by the check, based on
+  // the given language and clang-tidy options. It can return \c None to handle
+  // cases where the options disable the check.
+  //
+  // All cases in the rule generated by \p MakeRule must have a non-null \c
+  // Explanation, even though \c Explanation is optional for RewriteRule in
+  // general. Because the primary purpose of clang-tidy checks is to provide
+  // users with diagnostics, we assume that a missing explanation is a bug.  If
+  // no explanation is desired, indicate that explicitly (for example, by
+  // passing `text("no explanation")` to `makeRule` as the `Explanation`
+  // argument).
+  TransformerClangTidyCheck(std::function<Optional<tooling::RewriteRule>(
+                                const LangOptions &, const OptionsView &)>
+                                MakeRule,
+                            StringRef Name, ClangTidyContext *Context);
+
+  // Convenience overload of the constructor when the rule doesn't depend on any
+  // of the language or clang-tidy options.
   TransformerClangTidyCheck(tooling::RewriteRule R, StringRef Name,
                             ClangTidyContext *Context);
+
   void registerMatchers(ast_matchers::MatchFinder *Finder) final;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) final;
 
 private:
-  tooling::RewriteRule Rule;
+  Optional<tooling::RewriteRule> Rule;
 };
 
 } // namespace utils
diff --git a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
index 6b8763810e9..6e42be25d5f 100644
--- a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
@@ -18,16 +18,16 @@ namespace clang {
 namespace tidy {
 namespace utils {
 namespace {
+using tooling::change;
 using tooling::RewriteRule;
+using tooling::text;
+using tooling::stencil::cat;
 
 // Invert the code of an if-statement, while maintaining its semantics.
 RewriteRule invertIf() {
   using namespace ::clang::ast_matchers;
-  using tooling::change;
   using tooling::node;
   using tooling::statement;
-  using tooling::text;
-  using tooling::stencil::cat;
 
   StringRef C = "C", T = "T", E = "E";
   RewriteRule Rule = tooling::makeRule(
@@ -65,6 +65,62 @@ TEST(TransformerClangTidyCheckTest, Basic) {
   )";
   EXPECT_EQ(Expected, test::runCheckOnCode<IfInverterCheck>(Input));
 }
+
+// A trivial rewrite-rule generator that requires Objective-C code.
+Optional<RewriteRule> needsObjC(const LangOptions &LangOpts,
+                                const ClangTidyCheck::OptionsView &Options) {
+  if (!LangOpts.ObjC)
+    return None;
+  return tooling::makeRule(clang::ast_matchers::functionDecl(),
+                           change(cat("void changed() {}")), text("no message"));
+}
+
+class NeedsObjCCheck : public TransformerClangTidyCheck {
+public:
+  NeedsObjCCheck(StringRef Name, ClangTidyContext *Context)
+      : TransformerClangTidyCheck(needsObjC, Name, Context) {}
+};
+
+// Verify that the check only rewrites the code when the input is Objective-C.
+TEST(TransformerClangTidyCheckTest, DisableByLang) {
+  const std::string Input = "void log() {}";
+  EXPECT_EQ(Input,
+            test::runCheckOnCode<NeedsObjCCheck>(Input, nullptr, "input.cc"));
+
+  EXPECT_EQ("void changed() {}",
+            test::runCheckOnCode<NeedsObjCCheck>(Input, nullptr, "input.mm"));
+}
+
+// A trivial rewrite rule generator that checks config options.
+Optional<RewriteRule> noSkip(const LangOptions &LangOpts,
+                             const ClangTidyCheck::OptionsView &Options) {
+  if (Options.get("Skip", "false") == "true")
+    return None;
+  return tooling::makeRule(clang::ast_matchers::functionDecl(),
+                           change(cat("void nothing()")), text("no message"));
+}
+
+class ConfigurableCheck : public TransformerClangTidyCheck {
+public:
+  ConfigurableCheck(StringRef Name, ClangTidyContext *Context)
+      : TransformerClangTidyCheck(noSkip, Name, Context) {}
+};
+
+// Tests operation with config option "Skip" set to true and false.
+TEST(TransformerClangTidyCheckTest, DisableByConfig) {
+  const std::string Input = "void log(int);";
+  const std::string Expected = "void nothing();";
+  ClangTidyOptions Options;
+
+  Options.CheckOptions["test-check-0.Skip"] = "true";
+  EXPECT_EQ(Input, test::runCheckOnCode<ConfigurableCheck>(
+                       Input, nullptr, "input.cc", None, Options));
+
+  Options.CheckOptions["test-check-0.Skip"] = "false";
+  EXPECT_EQ(Expected, test::runCheckOnCode<ConfigurableCheck>(
+                          Input, nullptr, "input.cc", None, Options));
+}
+
 } // namespace
 } // namespace utils
 } // namespace tidy