[clang-tidy] Add check: replace string::find(...) == 0 with absl::StartsWith

Patch by Niko Weh!

Reviewers: hokein

Subscribers: klimek, cfe-commits, ioeric, ilya-biryukov, ahedberg

Differential Revision: https://reviews.llvm.org/D43847

llvm-svn: 327111

1 files changed, 133 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp
new file mode 100644
index 00000000000..44df264688a
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp
@@ -0,0 +1,133 @@
+//===--- StringFindStartswithCheck.cc - clang-tidy---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "StringFindStartswithCheck.h"
+
+#include "../utils/OptionsUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Frontend/CompilerInstance.h"
+
+#include <cassert>
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace abseil {
+
+StringFindStartswithCheck::StringFindStartswithCheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      StringLikeClasses(utils::options::parseStringList(
+          Options.get("StringLikeClasses", "::std::basic_string"))),
+      IncludeStyle(utils::IncludeSorter::parseIncludeStyle(
+          Options.getLocalOrGlobal("IncludeStyle", "llvm"))),
+      AbseilStringsMatchHeader(
+          Options.get("AbseilStringsMatchHeader", "absl/strings/match.h")) {}
+
+void StringFindStartswithCheck::registerMatchers(MatchFinder *Finder) {
+  auto ZeroLiteral = integerLiteral(equals(0));
+  auto StringClassMatcher = cxxRecordDecl(hasAnyName(SmallVector<StringRef, 4>(
+      StringLikeClasses.begin(), StringLikeClasses.end())));
+
+  auto StringFind = cxxMemberCallExpr(
+      // .find()-call on a string...
+      callee(cxxMethodDecl(hasName("find"), ofClass(StringClassMatcher))),
+      // ... with some search expression ...
+      hasArgument(0, expr().bind("needle")),
+      // ... and either "0" as second argument or the default argument (also 0).
+      anyOf(hasArgument(1, ZeroLiteral), hasArgument(1, cxxDefaultArgExpr())));
+
+  Finder->addMatcher(
+      // Match [=!]= with a zero on one side and a string.find on the other.
+      binaryOperator(
+          anyOf(hasOperatorName("=="), hasOperatorName("!=")),
+          hasEitherOperand(ignoringParenImpCasts(ZeroLiteral)),
+          hasEitherOperand(ignoringParenImpCasts(StringFind.bind("findexpr"))))
+          .bind("expr"),
+      this);
+}
+
+void StringFindStartswithCheck::check(const MatchFinder::MatchResult &Result) {
+  const ASTContext &Context = *Result.Context;
+  const SourceManager &Source = Context.getSourceManager();
+
+  // Extract matching (sub)expressions
+  const auto *ComparisonExpr = Result.Nodes.getNodeAs<BinaryOperator>("expr");
+  assert(ComparisonExpr != nullptr);
+  const auto *Needle = Result.Nodes.getNodeAs<Expr>("needle");
+  assert(Needle != nullptr);
+  const Expr *Haystack = Result.Nodes.getNodeAs<CXXMemberCallExpr>("findexpr")
+                             ->getImplicitObjectArgument();
+  assert(Haystack != nullptr);
+
+  if (ComparisonExpr->getLocStart().isMacroID())
+    return;
+
+  // Get the source code blocks (as characters) for both the string object
+  // and the search expression
+  const StringRef NeedleExprCode = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(Needle->getSourceRange()), Source,
+      Context.getLangOpts());
+  const StringRef HaystackExprCode = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(Haystack->getSourceRange()), Source,
+      Context.getLangOpts());
+
+  // Create the StartsWith string, negating if comparison was "!=".
+  bool Neg = ComparisonExpr->getOpcodeStr() == "!=";
+  StringRef StartswithStr;
+  if (Neg) {
+    StartswithStr = "!absl::StartsWith";
+  } else {
+    StartswithStr = "absl::StartsWith";
+  }
+
+  // Create the warning message and a FixIt hint replacing the original expr.
+  auto Diagnostic =
+      diag(ComparisonExpr->getLocStart(),
+           (StringRef("use ") + StartswithStr + " instead of find() " +
+            ComparisonExpr->getOpcodeStr() + " 0")
+               .str());
+
+  Diagnostic << FixItHint::CreateReplacement(
+      ComparisonExpr->getSourceRange(),
+      (StartswithStr + "(" + HaystackExprCode + ", " + NeedleExprCode + ")")
+          .str());
+
+  // Create a preprocessor #include FixIt hint (CreateIncludeInsertion checks
+  // whether this already exists).
+  auto IncludeHint = IncludeInserter->CreateIncludeInsertion(
+      Source.getFileID(ComparisonExpr->getLocStart()), AbseilStringsMatchHeader,
+      false);
+  if (IncludeHint) {
+    Diagnostic << *IncludeHint;
+  }
+}
+
+void StringFindStartswithCheck::registerPPCallbacks(
+    CompilerInstance &Compiler) {
+  IncludeInserter = llvm::make_unique<clang::tidy::utils::IncludeInserter>(
+      Compiler.getSourceManager(), Compiler.getLangOpts(), IncludeStyle);
+  Compiler.getPreprocessor().addPPCallbacks(
+      IncludeInserter->CreatePPCallbacks());
+}
+
+void StringFindStartswithCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "StringLikeClasses",
+                utils::options::serializeStringList(StringLikeClasses));
+  Options.store(Opts, "IncludeStyle",
+                utils::IncludeSorter::toString(IncludeStyle));
+  Options.store(Opts, "AbseilStringsMatchHeader", AbseilStringsMatchHeader);
+}
+
+} // namespace abseil
+} // namespace tidy
+} // namespace clang