[clang-tidy] Update IdentifierNamingCheck to remove extra leading/trailing underscores

[jtbandes]

Summary

The goal of this change is to fix the following suboptimal replacements currently suggested by clang-tidy:

// with MemberPrefix == "_"
int __foo;  // accepted without complaint

// with MemberPrefix == "m_"
int _foo;
    ^~~~~~
    m__foo

I fixed this by

• updating matchesStyle() to reject names which have a leading underscore after a prefix has already been stripped, or a trailing underscore if a suffix has already been stripped;
• updating fixupWithStyle() to strip leading & trailing underscores before adding the user-defined prefix and suffix.

The replacements are now:

// MemberPrefix == "_"
int __foo;
    ^~~~~~
    _foo

// MemberPrefix == "m_"
int _foo;
    ^~~~~
    m_foo

Future improvements might elect to add .clang-tidy flags to improve what is being stripped. For instance, stripping m_ could allow m_foo to be automatically replaced with _foo.

[jtbandes]

Remove unnecessary checks for empty prefix/suffix

[jtbandes]

Cleanup

[alexfh]

LG with a nit.

clang-tidy/readability/IdentifierNamingCheck.cpp

378

Mid.empty()

[jtbandes]

Fixed nit

[jtbandes]

Done, thanks for the review!

What is the procedure for merging patches in? I'm sure I don't have permissions to do it myself.

[alexfh]

In D32333#738266, @jtbandes wrote:

Done, thanks for the review!

What is the procedure for merging patches in? I'm sure I don't have permissions to do it myself.

I'll commit the patch for you.

Thank you for working on this!

clang-tidy/readability/IdentifierNamingCheck.cpp

static bool matchesStyle(StringRef Name,
   else
     Matches = false;
 
   if (Name.endswith(Style.Suffix))
     Name = Name.drop_back(Style.Suffix.size());
   else
     Matches = false;
 
+  // Ensure the name doesn't have any extra underscores beyond those specified
+  // in the prefix and suffix.
+  if (Name.startswith("_") || Name.endswith("_"))
+    Matches = false;
+
   if (Style.Case && !Matchers[static_cast<size_t>(*Style.Case)].match(Name))
     Matches = false;
 
   return Matches;
 }
 
 static std::string fixupWithCase(StringRef Name,
                                  IdentifierNamingCheck::CaseType Case) {
static std::string fixupWithCase(StringRef Name,
   }
 
   return Fixup;
 }
 
 static std::string
 fixupWithStyle(StringRef Name,
                const IdentifierNamingCheck::NamingStyle &Style) {
-  return Style.Prefix +
-         fixupWithCase(Name, Style.Case.getValueOr(
-                                 IdentifierNamingCheck::CaseType::CT_AnyCase)) +
-         Style.Suffix;
+  const std::string Fixed = fixupWithCase(
+      Name, Style.Case.getValueOr(IdentifierNamingCheck::CaseType::CT_AnyCase));
+  StringRef Mid = StringRef(Fixed).trim("_");
+  if (Mid.empty())
+    Mid = "_";
+  return (Style.Prefix + Mid + Style.Suffix).str();
 }
 
 static StyleKind findStyleKind(
     const NamedDecl *D,
     const std::vector<llvm::Optional<IdentifierNamingCheck::NamingStyle>>
         &NamingStyles) {
   if (isa<TypedefDecl>(D) && NamingStyles[SK_Typedef])
     return SK_Typedef;

test/clang-tidy/readability-identifier-naming.cpp

 
 private:
   const int MEMBER_one_1 = ConstExpr_variable;
 // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: invalid case style for constant member 'MEMBER_one_1'
 // CHECK-FIXES: {{^}}  const int member_one_1 = const_expr_variable;{{$}}
   int member2 = 2;
 // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: invalid case style for private member 'member2'
 // CHECK-FIXES: {{^}}  int __member2 = 2;{{$}}
+  int _memberWithExtraUnderscores_ = 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: invalid case style for private member '_memberWithExtraUnderscores_'
+// CHECK-FIXES: {{^}}  int __memberWithExtraUnderscores = 42;{{$}}
 
 private:
     int private_member = 3;
 // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: invalid case style for private member 'private_member'
 // CHECK-FIXES: {{^}}    int __private_member = 3;{{$}}
 
 protected:
     int ProtMember;