[PATCH] D62340: [clang-tidy] In TransformerClangTidyCheck, require Explanation field.

[Yitzhak Mandelbaum via Phabricator via cfe-commits]

ymandel created this revision.
ymandel added a reviewer: ilya-biryukov.
Herald added a subscriber: xazax.hun.
Herald added a project: clang.

In general, the `Explanation` field is optional in `RewriteRule` cases. But,
because the primary purpose of clang-tidy checks is to provide users with
diagnostics, we assume that a missing explanation is a bug.  This change adds an
assertion that checks all cases for an explanation, and updates the code to rely
on that assertion correspondingly.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62340

Files:
  clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
  clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
  clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp


Index: clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
===================================================================
--- clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
+++ clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
@@ -29,12 +29,14 @@
   using tooling::stencil::cat;
 
   StringRef C = "C", T = "T", E = "E";
-  return tooling::makeRule(ifStmt(hasCondition(expr().bind(C)),
+  RewriteRule Rule = tooling::makeRule(ifStmt(hasCondition(expr().bind(C)),
                                   hasThen(stmt().bind(T)),
                                   hasElse(stmt().bind(E))),
                            change(statement(RewriteRule::RootID),
                                   cat("if(!(", node(C), ")) ", statement(E),
                                       " else ", statement(T))));
+  Rule.Cases[0].Explanation = tooling::text("no explanation");
+  return Rule;
 }
 
 class IfInverterCheck : public TransformerClangTidyCheck {
Index: clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
===================================================================
--- clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
+++ clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
@@ -29,12 +29,17 @@
 //   MyCheck(StringRef Name, ClangTidyContext *Context)
 //       : TransformerClangTidyCheck(MyCheckAsRewriteRule, Name, Context) {}
 // };
+//
 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, `MyRule.Case[0].Explanation =
+  // text("no explanation")`).
   TransformerClangTidyCheck(tooling::RewriteRule R, StringRef Name,
-                            ClangTidyContext *Context)
-      : ClangTidyCheck(Name, Context), Rule(std::move(R)) {}
-
+                            ClangTidyContext *Context);
   void registerMatchers(ast_matchers::MatchFinder *Finder) final;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) final;
 
Index: clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
+++ clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
@@ -13,6 +13,17 @@
 namespace utils {
 using tooling::RewriteRule;
 
+TransformerClangTidyCheck::TransformerClangTidyCheck(tooling::RewriteRule R,
+                                                     StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context), Rule(std::move(R)) {
+  for (const auto &Case : Rule.Cases) {
+    assert(Case.Explanation != nullptr &&
+           "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);
@@ -44,15 +55,13 @@
   if (Transformations->empty())
     return;
 
-  StringRef Message = "no explanation";
-  if (Case.Explanation) {
-    if (Expected<std::string> E = Case.Explanation(Result))
-      Message = *E;
-    else
-      llvm::errs() << "Error in explanation: " << llvm::toString(E.takeError())
-                   << "\n";
+  Expected<std::string> Explanation = Case.Explanation(Result);
+  if (!Explanation) {
+    llvm::errs() << "Error in explanation: "
+                 << llvm::toString(Explanation.takeError()) << "\n";
+    return;
   }
-  DiagnosticBuilder Diag = diag(RootLoc, Message);
+  DiagnosticBuilder Diag = diag(RootLoc, *Explanation);
   for (const auto &T : *Transformations) {
     Diag << FixItHint::CreateReplacement(T.Range, T.Replacement);
   }


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