Adds the NSDateFormatter checker to clang-tidy

Differential Revision: https://reviews.llvm.org/D126097

4 files changed, 157 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/objc/CMakeLists.txt b/clang-tools-extra/clang-tidy/objc/CMakeLists.txt
index 1129c6a..bdd125c 100644
--- a/clang-tools-extra/clang-tidy/objc/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/objc/CMakeLists.txt
@@ -10,6 +10,7 @@ add_clang_library(clangTidyObjCModule
   ForbiddenSubclassingCheck.cpp
   MissingHashCheck.cpp
   NSInvocationArgumentLifetimeCheck.cpp
+  NSDateFormatterCheck.cpp
   ObjCTidyModule.cpp
   PropertyDeclarationCheck.cpp
   SuperSelfCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp
new file mode 100644
index 0000000..fdc8377
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp
@@ -0,0 +1,116 @@
+//===--- NSDateFormatterCheck.cpp - clang-tidy ----------------------------===//
+//
+// 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 "NSDateFormatterCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace objc {
+
+void NSDateFormatterCheck::registerMatchers(MatchFinder *Finder) {
+  // Adding matchers.
+
+  Finder->addMatcher(
+      objcMessageExpr(hasSelector("setDateFormat:"),
+                      hasReceiverType(asString("NSDateFormatter *")),
+                      hasArgument(0, ignoringImpCasts(
+                                         objcStringLiteral().bind("str_lit")))),
+      this);
+}
+
+static char ValidDatePatternChars[] = {
+    'G', 'y', 'Y', 'u', 'U', 'r', 'Q', 'q', 'M', 'L', 'I', 'w', 'W', 'd',
+    'D', 'F', 'g', 'E', 'e', 'c', 'a', 'b', 'B', 'h', 'H', 'K', 'k', 'j',
+    'J', 'C', 'm', 's', 'S', 'A', 'z', 'Z', 'O', 'v', 'V', 'X', 'x'};
+
+// Checks if the string pattern used as a date format specifier is valid.
+// A string pattern is valid if all the letters(a-z, A-Z) in it belong to the
+// set of reserved characters. See:
+// https://www.unicode.org/reports/tr35/tr35.html#Invalid_Patterns
+bool isValidDatePattern(StringRef Pattern) {
+  for (auto &PatternChar : Pattern) {
+    if (isalpha(PatternChar)) {
+      if (std::find(std::begin(ValidDatePatternChars),
+                    std::end(ValidDatePatternChars),
+                    PatternChar) == std::end(ValidDatePatternChars)) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+// Checks if the string pattern used as a date format specifier contains
+// any incorrect pattern and reports it as a warning.
+// See: http://www.unicode.org/reports/tr35/tr35-dates.html#Date_Format_Patterns
+void NSDateFormatterCheck::check(const MatchFinder::MatchResult &Result) {
+  // Callback implementation.
+  const auto *StrExpr = Result.Nodes.getNodeAs<ObjCStringLiteral>("str_lit");
+  const StringLiteral *SL = cast<ObjCStringLiteral>(StrExpr)->getString();
+  StringRef SR = SL->getString();
+
+  if (!isValidDatePattern(SR)) {
+    diag(StrExpr->getExprLoc(), "invalid date format specifier");
+  }
+
+  if (SR.contains('y') && SR.contains('w') && !SR.contains('Y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of calendar year (y) with week of the year (w); "
+         "did you mean to use week-year (Y) instead?");
+  }
+  if (SR.contains('F')) {
+    if (!(SR.contains('e') || SR.contains('E'))) {
+      diag(StrExpr->getExprLoc(),
+           "day of week in month (F) used without day of the week (e or E); "
+           "did you forget e (or E) in the format string?");
+    }
+    if (!SR.contains('M')) {
+      diag(StrExpr->getExprLoc(),
+           "day of week in month (F) used without the month (M); "
+           "did you forget M in the format string?");
+    }
+  }
+  if (SR.contains('W') && !SR.contains('M')) {
+    diag(StrExpr->getExprLoc(), "Week of Month (W) used without the month (M); "
+                                "did you forget M in the format string?");
+  }
+  if (SR.contains('Y') && SR.contains('Q') && !SR.contains('y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of week year (Y) with quarter number (Q); "
+         "did you mean to use calendar year (y) instead?");
+  }
+  if (SR.contains('Y') && SR.contains('M') && !SR.contains('y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of week year (Y) with month (M); "
+         "did you mean to use calendar year (y) instead?");
+  }
+  if (SR.contains('Y') && SR.contains('D') && !SR.contains('y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of week year (Y) with day of the year (D); "
+         "did you mean to use calendar year (y) instead?");
+  }
+  if (SR.contains('Y') && SR.contains('W') && !SR.contains('y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of week year (Y) with week of the month (W); "
+         "did you mean to use calendar year (y) instead?");
+  }
+  if (SR.contains('Y') && SR.contains('F') && !SR.contains('y')) {
+    diag(StrExpr->getExprLoc(),
+         "use of week year (Y) with day of the week in month (F); "
+         "did you mean to use calendar year (y) instead?");
+  }
+}
+
+} // namespace objc
+} // namespace tidy
+} // namespace clang
diff --git a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h
new file mode 100644
index 0000000..f2c6f5f
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h
@@ -0,0 +1,38 @@
+//===--- NSDateFormatterCheck.h - clang-tidy --------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_NSDATEFORMATTERCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_NSDATEFORMATTERCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang {
+namespace tidy {
+namespace objc {
+
+/// Checks the string pattern used as a date format specifier and reports
+/// warnings if it contains any incorrect sub-pattern.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/objc-NSDateFormatter.html
+class NSDateFormatterCheck : public ClangTidyCheck {
+public:
+  NSDateFormatterCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.ObjC;
+  }
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace objc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_NSDATEFORMATTERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
index 3a5bf7d..0cfab1f 100644
--- a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
@@ -14,6 +14,7 @@
 #include "DeallocInCategoryCheck.h"
 #include "ForbiddenSubclassingCheck.h"
 #include "MissingHashCheck.h"
+#include "NSDateFormatterCheck.h"
 #include "NSInvocationArgumentLifetimeCheck.h"
 #include "PropertyDeclarationCheck.h"
 #include "SuperSelfCheck.h"
@@ -37,6 +38,7 @@ public:
         "objc-forbidden-subclassing");
     CheckFactories.registerCheck<MissingHashCheck>(
         "objc-missing-hash");
+    CheckFactories.registerCheck<NSDateFormatterCheck>("objc-nsdate-formatter");
     CheckFactories.registerCheck<NSInvocationArgumentLifetimeCheck>(
         "objc-nsinvocation-argument-lifetime");
     CheckFactories.registerCheck<PropertyDeclarationCheck>(