[clang-tidy] readability-container-size-empty handle std::string length()

[PiotrZSL]

Summary

Extends readability-container-size-empty to check std::string length() similar to size().

Fixes: #37603

Co-authored-by: Dmitry Venikov <[e-mail]>

[lebedev.ri]

Either this is a NFC change with just tests, or the actual fix is missing.

[Quolyk]

For now, I just added tests. I have several questions, as I'm beginner (ContainerSizeEmptyCheck.cpp).

1. Do I have to extend ValidContainer, so it recognises ::std::string with length() method as valid container too or we can assume ::std::string as valid container by default?
2. If ::std::string is valid container, I just add one more expression to match. Is it correct way?

[Quolyk]

In D56644#1355434, @lebedev.ri wrote:

Either this is a NFC change with just tests, or the actual fix is missing.

Right, it's WIP for now.

[lebedev.ri]

In D56644#1355436, @Quolyk wrote:

For now, I just added tests. I have several questions, as I'm beginner (ContainerSizeEmptyCheck.cpp).

1. Do I have to extend ValidContainer, so it recognises ::std::string with length() method as valid container too or we can assume ::std::string as valid container by default?
2. If ::std::string is valid container, I just add one more expression to match. Is it correct way?

https://github.com/llvm-mirror/clang-tools-extra/blob/27011d1db0ee4955bab595ab51ebe264e160ed89/clang-tidy/readability/ContainerSizeEmptyCheck.cpp#L40
i think you want to change ValidContainer to not only check for size, but for size or lenght.
I.e. replace hasName("lenght"), with anyOf(hasName("size"), hasName("lenght")),.
And then adjust the diags to dynamically get the actual method name.

[Quolyk]

Update tests. Handle length.

[lebedev.ri]

Seems to look good.

clang-tidy/readability/ContainerSizeEmptyCheck.cpp

65

This line looks too long, clang-format might be too intrusive, so at least

callee(cxxMethodDecl(anyOf(hasName("size"), 
                           hasName("length")))),
WrongUse,

test/clang-tidy/readability-container-size-empty.cpp

19–20

Does it still work if only one of these exists?

[Quolyk]

test/clang-tidy/readability-container-size-empty.cpp

19–20

It works indeed, do you suggest adding test case for this?

[lebedev.ri]

clang-tidy/readability/ContainerSizeEmptyCheck.cpp

34

auto ContainerLenghtFuncNames = anyOf(hasName("size"), hasName("length"));

pick better naem

40

s/anyOf(hasName("size"), hasName("length")),/ContainerLenghtFuncNames,/

40–65

We want anyOf() in both cases, with the same list of suspects.
If it is not a anyOf() in the second case, then naturally it won't work (can't have more than one name)
If it is not a anyOf() in the first case, then it will e.g. work if all of them are present.
So we just want to ensure that we do the same thing in both cases.

65

s/callee(cxxMethodDecl(anyOf(hasName("size"), hasName("length")))), WrongUse,/callee(cxxMethodDecl(ContainerLenghtFuncNames)), WrongUse,/

test/clang-tidy/readability-container-size-empty.cpp

19–20

Hmm, actually, i think there is an easier solution, see other inline comment.

[Eugene.Zelenko]

It'll be worth to mention change in Release Notes (in changes list, in alphabetical order).

[JonasToth]

Could you please run it over LLVM or another significant codebase and check if there are miss-transformations (run with fix and then compile (+ tests optimally))?
You can use clang-tidy/tool/run-clang-tidy.py for a parallel runner.

[MyDeveloperDay]

test/clang-tidy/readability-container-size-empty.cpp

135

could you add a test that checks if StringRef.str().length() >0 becomes !StringRef.str.empty()

e.g.

LLVM::StringRef ArgRef;
....
return (ArgRef.str().length() > 0) ? ArgRef.str() + ")" : "()";

[alexfh]

clang-tidy/readability/ContainerSizeEmptyCheck.cpp

65

Please use hasAnyName(x, y) instead of anyOf(hasName(x), hasName(y)). It's shorter and executes faster (the more arguments it has, the faster it is compared to the corresponding anyOf(hasName(...), ...) construct).

207

Did you try without ->getName()? IIUC, it should work as well.

[JonasToth]

any news here? do you plan to finish this patch @Quolyk ?
Do you mind if someone comandeers this patch?

[Eugene.Zelenko]

It'll be great to finalize patch and close issue #37603.

[LegalizeAdulthood]

Clang-Tidy tests and docs have moved to module subdirectories.

Please rebase this onto main:HEAD and:

• fold your changes into the appropriate subdirs, stripping the module prefix from new files.
• make the target check-clang-extra to validate your tests
• make the target docs-clang-tools-html to validate any docs changes

[PiotrZSL]

rebase, add support for dependent context, update documentation

[PiotrZSL]

test/clang-tidy/readability-container-size-empty.cpp

135

No point, should work anyway.

[PiotrZSL]

Rebase + Ping

[carlosgalvezp]

LGTM!

clang-tidy/readability/ContainerSizeEmptyCheck.cpp

ContainerSizeEmptyCheck::ContainerSizeEmptyCheck(StringRef Name,
                                                  ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context) {}
 
 void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
   // Only register the matchers for C++; the functionality currently does not
   // provide any benefit to other languages, despite being benign.
   if (!getLangOpts().CPlusPlus)
     return;
 
   const auto ValidContainer = qualType(hasUnqualifiedDesugaredType(
       recordType(hasDeclaration(cxxRecordDecl(isSameOrDerivedFrom(
           namedDecl(
               has(cxxMethodDecl(
                       isConst(), parameterCountIs(0), isPublic(),
-                      hasName("size"),
+                      anyOf(hasName("size"), hasName("length")),
                       returns(qualType(isInteger(), unless(booleanType()))))
                       .bind("size")),
               has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
                                 hasName("empty"), returns(booleanType()))
                       .bind("empty")))
               .bind("container")))))));
 
   const auto WrongUse = anyOf(
       hasParent(binaryOperator(
                     matchers::isComparisonOperator(),
                     hasEitherOperand(ignoringImpCasts(anyOf(
                         integerLiteral(equals(1)), integerLiteral(equals(0))))))
                     .bind("SizeBinaryOp")),
       hasParent(implicitCastExpr(
           hasImplicitDestinationType(booleanType()),
           anyOf(
               hasParent(unaryOperator(hasOperatorName("!")).bind("NegOnSize")),
               anything()))),
       hasParent(explicitCastExpr(hasDestinationType(booleanType()))));
 
   Finder->addMatcher(
       cxxMemberCallExpr(on(expr(anyOf(hasType(ValidContainer),
                                       hasType(pointsTo(ValidContainer)),
                                       hasType(references(ValidContainer))))),
-                        callee(cxxMethodDecl(hasName("size"))), WrongUse,
+                        callee(cxxMethodDecl(anyOf(hasName("size"), hasName("length")))), WrongUse,
                         unless(hasAncestor(cxxMethodDecl(
                             ofClass(equalsBoundNode("container"))))))
           .bind("SizeCallExpr"),
       this);
 
   // Empty constructor matcher.
   const auto DefaultConstructor = cxxConstructExpr(
           hasDeclaration(cxxConstructorDecl(isDefaultConstructor())));
if (BinCmp) {
     else
       Hint = FixItHint::CreateReplacement(MemberCall->getSourceRange(),
                                           "!" + ReplacementText);
   }
 
   if (MemberCall) {
     diag(MemberCall->getBeginLoc(),
          "the 'empty' method should be used to check "
-         "for emptiness instead of 'size'")
+         "for emptiness instead of '%0'")
+        << MemberCall->getMethodDecl()->getName()
         << Hint;
   } else {
     diag(BinCmp->getBeginLoc(),
          "the 'empty' method should be used to check "
          "for emptiness instead of comparing to an empty object")
         << Hint;
   }
 

test/clang-tidy/readability-container-size-empty.cpp

 
 template <typename T> struct basic_string {
   basic_string();
   bool operator==(const basic_string<T>& other) const;
   bool operator!=(const basic_string<T>& other) const;
   bool operator==(const char *) const;
   bool operator!=(const char *) const;
   basic_string<T> operator+(const basic_string<T>& other) const;
   unsigned long size() const;
+  unsigned long length() const;
   bool empty() const;
 };
 
 typedef basic_string<char> string;
 typedef basic_string<wchar_t> wstring;
 
 inline namespace __v2 {
 template <typename T> struct set {

 }
 
 int main() {
   std::set<int> intSet;
   std::string str;
   std::string str2;
   std::wstring wstr;
   (void)(str.size() + 0);
+  (void)(str.length() + 0);
   (void)(str.size() - 0);
+  (void)(str.length() - 0);
   (void)(0 + str.size());
+  (void)(0 + str.length());
   (void)(0 - str.size());
+  (void)(0 - str.length());
   if (intSet.size() == 0)
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (intSet.empty()){{$}}
-  // CHECK-MESSAGES: :32:8: note: method 'set'::empty() defined here
+  // CHECK-MESSAGES: :33:8: note: method 'set'::empty() defined here
   if (intSet == std::set<int>())
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness
   // CHECK-FIXES: {{^  }}if (intSet.empty()){{$}}
-  // CHECK-MESSAGES: :32:8: note: method 'set'::empty() defined here
+  // CHECK-MESSAGES: :33:8: note: method 'set'::empty() defined here
   if (s_func() == "")
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if (s_func().empty()){{$}}
   if (str.size() == 0)
     ;
-  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
+  // CHECK-FIXES: {{^  }}if (str.empty()){{$}}
+  if (str.length() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'length' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (str.empty()){{$}}
   if ((str + str2).size() == 0)
     ;
-  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
+  // CHECK-FIXES: {{^  }}if ((str + str2).empty()){{$}}
+  if ((str + str2).length() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'length' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if ((str + str2).empty()){{$}}
   if (str == "")
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if (str.empty()){{$}}
   if (str + str2 == "")
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if ((str + str2).empty()){{$}}
   if (wstr.size() == 0)
     ;
-  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
+  // CHECK-FIXES: {{^  }}if (wstr.empty()){{$}}
+  if (wstr.length() == 0)
+    ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'length' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (wstr.empty()){{$}}
   if (wstr == "")
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if (wstr.empty()){{$}}
   std::vector<int> vect;
   if (vect.size() == 0)
     ;
-  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
+  // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty]
   // CHECK-FIXES: {{^  }}if (vect.empty()){{$}}
   if (vect == std::vector<int>())
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
   // CHECK-FIXES: {{^  }}if (vect.empty()){{$}}
   if (vect.size() != 0)
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
template <typename T> void f() {
   // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: the 'empty' method should be used
   // CHECK-MESSAGES: :9:8: note: method 'vector'::empty() defined here
   // CHECK-FIXES: CHECKSIZE(v);
 
   TemplatedContainer<T> templated_container;
   if (templated_container.size())
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
-  // CHECK-MESSAGES: :44:8: note: method 'TemplatedContainer'::empty() defined here
+  // CHECK-MESSAGES: :45:8: note: method 'TemplatedContainer'::empty() defined here
   // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
   if (templated_container != TemplatedContainer<T>())
     ;
   // CHECK-MESSAGES: :[[@LINE-2]]:7: warning: the 'empty' method should be used
-  // CHECK-MESSAGES: :44:8: note: method 'TemplatedContainer'::empty() defined here
+  // CHECK-MESSAGES: :45:8: note: method 'TemplatedContainer'::empty() defined here
   // CHECK-FIXES: {{^  }}if (!templated_container.empty()){{$}}
   // CHECK-FIXES-NEXT: ;
   CHECKSIZE(templated_container);
   // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: the 'empty' method should be used
-  // CHECK-MESSAGES: :44:8: note: method 'TemplatedContainer'::empty() defined here
+  // CHECK-MESSAGES: :45:8: note: method 'TemplatedContainer'::empty() defined here
   // CHECK-FIXES: CHECKSIZE(templated_container);
 }
 
 void g() {
   f<int>();
   f<double>();
   f<char *>();
 }