Adds the NSDateFormatter checker to clang-tidy

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

Author: t-rasmud

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

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

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

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 @@ class ObjCModule : public ClangTidyModule {
         "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>(

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -239,7 +239,6 @@ Clang-Tidy Checks
    `llvmlibc-implementation-in-namespace <llvmlibc/implementation-in-namespace.html>`_,
    `llvmlibc-restrict-system-libc-headers <llvmlibc/restrict-system-libc-headers.html>`_, "Yes"
    `misc-confusable-identifiers <misc/confusable-identifiers.html>`_,
-   `misc-const-correctness <misc/const-correctness.html>`_, "Yes"
    `misc-definitions-in-headers <misc/definitions-in-headers.html>`_, "Yes"
    `misc-misleading-bidirectional <misc/misleading-bidirectional.html>`_,
    `misc-misleading-identifier <misc/misleading-identifier.html>`_,
@@ -295,6 +294,7 @@ Clang-Tidy Checks
    `objc-dealloc-in-category <objc/dealloc-in-category.html>`_,
    `objc-forbidden-subclassing <objc/forbidden-subclassing.html>`_,
    `objc-missing-hash <objc/missing-hash.html>`_,
+   `objc-nsdate-formatter <objc/nsdate-formatter.html>`_,
    `objc-nsinvocation-argument-lifetime <objc/nsinvocation-argument-lifetime.html>`_, "Yes"
    `objc-property-declaration <objc/property-declaration.html>`_, "Yes"
    `objc-super-self <objc/super-self.html>`_, "Yes"

clang-tools-extra/docs/clang-tidy/checks/objc/nsdate-formatter.rst

@@ -0,0 +1,73 @@
+.. title:: clang-tidy - objc-nsdate-formatter
+
+objc-nsdate-formatter
+=====================
+
+When ``NSDateFormatter`` is used to convert an ``NSDate`` type to a ``String`` type, the user
+can specify a custom format string. Certain format specifiers are undesirable
+despite being legal. See http://www.unicode.org/reports/tr35/tr35-dates.html#Date_Format_Patterns for all legal date patterns.
+
+This checker reports as warnings the following string patterns in a date format specifier:
+
+#. yyyy + ww : Calendar year specified with week of a week year (unless YYYY is also specified).
+  
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `yyyy-ww`; 
+     | Output string: `2014-01` (Wrong because it’s not the first week of 2014)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `dd-MM-yyyy (ww-YYYY)`; 
+     | Output string: `29-12-2014 (01-2015)` (This is correct)
+    
+#. F without ee/EE : Numeric day of week in a month without actual day.
+    
+   * | **Example:** Input Date: `29 December 2014` ; Format String: `F-MM`; 
+     | Output string: `5-12` (Wrong because it reads as *5th ___ of Dec* in English)
+    
+#. F without MM : Numeric day of week in a month without month.
+   
+   * | **Example:** Input Date: `29 December 2014` ; Format String: `F-EE`
+     | Output string: `5-Mon` (Wrong because it reads as *5th Mon of ___* in English)
+    
+#. WW without MM : Week of the month without the month.
+   
+   * | **Example:** Input Date: `29 December 2014` ; Format String: `WW-yyyy`
+     | Output string: `05-2014` (Wrong because it reads as *5th Week of ___* in English)
+    
+#. YYYY + QQ : Week year specified with quarter of normal year (unless yyyy is also specified).
+   
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `YYYY-QQ`
+     | Output string: `2015-04` (Wrong because it’s not the 4th quarter of 2015)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `ww-YYYY (QQ-yyyy)`
+     | Output string: `01-2015 (04-2014)` (This is correct)
+    
+#. YYYY + MM :  Week year specified with Month of a calendar year (unless yyyy is also specified).
+    
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `YYYY-MM`
+     | Output string: `2015-12` (Wrong because it’s not the 12th month of 2015)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `ww-YYYY (MM-yyyy)`
+     | Output string: `01-2015 (12-2014)` (This is correct)
+    
+#. YYYY + DD : Week year with day of a calendar year (unless yyyy is also specified).
+    
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `YYYY-DD`
+     | Output string: `2015-363` (Wrong because it’s not the 363rd day of 2015)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `ww-YYYY (DD-yyyy)`
+     | Output string: `01-2015 (363-2014)` (This is correct)
+    
+#. YYYY + WW : Week year with week of a calendar year (unless yyyy is also specified).
+    
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `YYYY-WW`
+     | Output string: `2015-05` (Wrong because it’s not the 5th week of 2015)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `ww-YYYY (WW-MM-yyyy)`
+     | Output string: `01-2015 (05-12-2014)` (This is correct)
+    
+#. YYYY + F : Week year with day of week in a calendar month (unless yyyy is also specified).
+    
+   * | **Example 1:** Input Date: `29 December 2014` ; Format String: `YYYY-ww-F-EE`
+     | Output string: `2015-01-5-Mon` (Wrong because it’s not the 5th Monday of January in 2015)
+    
+   * | **Example 2:** Input Date: `29 December 2014` ; Format String: `ww-YYYY (F-EE-MM-yyyy)`
+     | Output string: `01-2015 (5-Mon-12-2014)` (This is correct)