[clang-tools-extra] [clang-tidy] Add new check readability-trailing-comma (PR #173669)

[Baranov Victor via cfe-commits]

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@@ -0,0 +1,171 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "TrailingCommaCheck.h"
+#include "../utils/LexerUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy {
+
+template <>
+struct OptionEnumMapping<readability::TrailingCommaCheck::CommaPolicyKind> {
+  static llvm::ArrayRef<
+      std::pair<readability::TrailingCommaCheck::CommaPolicyKind, StringRef>>
+  getEnumMapping() {
+    static constexpr std::pair<readability::TrailingCommaCheck::CommaPolicyKind,
+                               StringRef>
+        Mapping[] = {
+            {readability::TrailingCommaCheck::CommaPolicyKind::Append,
+             "Append"},
+            {readability::TrailingCommaCheck::CommaPolicyKind::Remove,
+             "Remove"},
+            {readability::TrailingCommaCheck::CommaPolicyKind::Ignore,
+             "Ignore"},
+        };
+    return {Mapping};
+  }
+};
+
+} // namespace clang::tidy
+
+namespace clang::tidy::readability {
+
+static bool isSingleLine(SourceLocation Begin, SourceLocation End,
+                         const SourceManager &SM) {
+  return SM.getExpansionLineNumber(Begin) == SM.getExpansionLineNumber(End);
+}
+
+namespace {
+
+AST_POLYMORPHIC_MATCHER(isMacro,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(EnumDecl,
+                                                        InitListExpr)) {
+  return Node.getBeginLoc().isMacroID() || Node.getEndLoc().isMacroID();
+}
+
+AST_MATCHER(EnumDecl, isEmptyEnum) { return Node.enumerators().empty(); }
+
+AST_MATCHER(InitListExpr, isEmptyInitList) { return Node.getNumInits() == 0; }
+
+} // namespace
+
+TrailingCommaCheck::TrailingCommaCheck(StringRef Name,
+                                       ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      SingleLineCommaPolicy(
+          Options.get("SingleLineCommaPolicy", CommaPolicyKind::Remove)),
+      MultiLineCommaPolicy(
+          Options.get("MultiLineCommaPolicy", CommaPolicyKind::Append)) {
+  if (SingleLineCommaPolicy == CommaPolicyKind::Ignore &&
+      MultiLineCommaPolicy == CommaPolicyKind::Ignore)
+    configurationDiag("The check '%0' will not perform any analysis because "
+                      "'SingleLineCommaPolicy' and 'MultiLineCommaPolicy' are "
+                      "both set to 'Ignore'.")
+        << Name;
+}
+
+void TrailingCommaCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "SingleLineCommaPolicy", SingleLineCommaPolicy);
+  Options.store(Opts, "MultiLineCommaPolicy", MultiLineCommaPolicy);
+}
+
+void TrailingCommaCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      enumDecl(isDefinition(), unless(isEmptyEnum()), unless(isMacro()))
+          .bind("enum"),
+      this);
+
+  Finder->addMatcher(initListExpr(unless(isEmptyInitList()), unless(isMacro()))
+                         .bind("initlist"),
+                     this);
+}
+
+void TrailingCommaCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *Enum = Result.Nodes.getNodeAs<EnumDecl>("enum"))
+    checkEnumDecl(Enum, Result);
+  else if (const auto *InitList =
+               Result.Nodes.getNodeAs<InitListExpr>("initlist"))
+    checkInitListExpr(InitList, Result);
+  else
+    llvm_unreachable("No matches found");
+}
+
+void TrailingCommaCheck::checkEnumDecl(const EnumDecl *Enum,
+                                       const MatchFinder::MatchResult &Result) {
+  const bool IsSingleLine = isSingleLine(Enum->getBeginLoc(), Enum->getEndLoc(),
+                                         *Result.SourceManager);
+  const CommaPolicyKind Policy =
+      IsSingleLine ? SingleLineCommaPolicy : MultiLineCommaPolicy;
+
+  if (Policy == CommaPolicyKind::Ignore)
+    return;
+
+  const std::optional<Token> LastTok =
+      Lexer::findPreviousToken(Enum->getBraceRange().getEnd(),
+                               *Result.SourceManager, getLangOpts(), false);
+
+  emitDiag(LastTok->getLocation(), LastTok, DiagKind::Enum, Result, Policy);
+}
+
+void TrailingCommaCheck::checkInitListExpr(
+    const InitListExpr *InitList, const MatchFinder::MatchResult &Result) {
+  // We need to use non-empty syntactic form for correct source locations.
+  if (const InitListExpr *SynInitInitList = InitList->getSyntacticForm();
+      SynInitInitList && SynInitInitList->getNumInits() > 0)
+    InitList = SynInitInitList;
+
+  const bool IsSingleLine = isSingleLine(
+      InitList->getBeginLoc(), InitList->getEndLoc(), *Result.SourceManager);
+  const CommaPolicyKind Policy =
+      IsSingleLine ? SingleLineCommaPolicy : MultiLineCommaPolicy;
+
+  if (Policy == CommaPolicyKind::Ignore)
+    return;
+
+  const Expr *LastInit = LastInit = InitList->inits().back();
----------------
vbvictor wrote:

Indeed silly mistake, I'll maybe look inside this diagnostic and try to improve it.

https://github.com/llvm/llvm-project/pull/173669