[clang-tidy] Improve google-objc-function-naming diagnostics 📙

Summary:
The diagnostics from google-objc-function-naming check will be more
actionable if they provide a brief description of the requirements from
the Google Objective-C style guide. The more descriptive diagnostics may
help clarify that functions in the global namespace must have an
appropriate prefix followed by Pascal case (engineers working previously
with static functions might not immediately understand the different
requirements of static and non-static functions).

Test Notes:
Verified against the clang-tidy tests.

Reviewers: benhamilton, aaron.ballman

Reviewed By: benhamilton

Subscribers: MyDeveloperDay, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D55482

2 files changed, 28 insertions, 14 deletions

diff --git a/clang-tools-extra/test/clang-tidy/google-objc-function-naming.m b/clang-tools-extra/test/clang-tidy/google-objc-function-naming.m
index 8ca90f0f09d..d0336d267cf 100644
--- a/clang-tools-extra/test/clang-tidy/google-objc-function-naming.m
+++ b/clang-tools-extra/test/clang-tidy/google-objc-function-naming.m
@@ -3,28 +3,35 @@
 typedef _Bool bool;
 
 static bool ispositive(int a) { return a > 0; }
-// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: function name 'ispositive' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: static function named 'ispositive'
+// must be in Pascal case as required by Google Objective-C style guide
 // CHECK-FIXES: static bool Ispositive(int a) { return a > 0; }
 
 static bool is_positive(int a) { return a > 0; }
-// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: function name 'is_positive' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: static function named 'is_positive'
+// must be in Pascal case as required by Google Objective-C style guide
 // CHECK-FIXES: static bool IsPositive(int a) { return a > 0; }
 
 static bool isPositive(int a) { return a > 0; }
-// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: function name 'isPositive' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: static function named 'isPositive'
+// must be in Pascal case as required by Google Objective-C style guide
 // CHECK-FIXES: static bool IsPositive(int a) { return a > 0; }
 
 static bool Is_Positive(int a) { return a > 0; }
-// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: function name 'Is_Positive' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: static function named 'Is_Positive'
+// must be in Pascal case as required by Google Objective-C style guide
 // CHECK-FIXES: static bool IsPositive(int a) { return a > 0; }
 
 static bool IsPositive(int a) { return a > 0; }
 
 bool ispalindrome(const char *str);
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'ispalindrome' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'ispalindrome' must have an appropriate prefix followed by Pascal case as
+// required by Google Objective-C style guide
 
 static const char *md5(const char *str) { return 0; }
-// CHECK-MESSAGES: :[[@LINE-1]]:20: warning: function name 'md5' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:20: warning: static function named 'md5' must be
+// in Pascal case as required by Google Objective-C style guide
 // CHECK-FIXES: static const char *Md5(const char *str) { return 0; }
 
 static const char *MD5(const char *str) { return 0; }
@@ -38,12 +45,16 @@ static const char *DEFFooURL(void) { return "https://clang.llvm.org/"; }
 static const char *StringFromNSString(id str) { return ""; }
 
 void ABLog_String(const char *str);
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'ABLog_String' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'ABLog_String' must have an appropriate prefix followed by Pascal case as
+// required by Google Objective-C style guide
 
 void ABLogString(const char *str);
 
 bool IsPrime(int a);
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'IsPrime' not using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'IsPrime' must have an appropriate prefix followed by Pascal case as required
+// by Google Objective-C style guide
 
 const char *ABURL(void) { return "https://clang.llvm.org/"; }
 
diff --git a/clang-tools-extra/test/clang-tidy/google-objc-function-naming.mm b/clang-tools-extra/test/clang-tidy/google-objc-function-naming.mm
index 2e894575528..43c2d7ebf67 100644
--- a/clang-tools-extra/test/clang-tidy/google-objc-function-naming.mm
+++ b/clang-tools-extra/test/clang-tidy/google-objc-function-naming.mm
@@ -1,16 +1,19 @@
 // RUN: %check_clang_tidy %s google-objc-function-naming %t
 
 void printSomething() {}
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'printSomething' not
-// using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'printSomething' must have an appropriate prefix followed by Pascal case as
+// required by Google Objective-C style guide
 
 void PrintSomething() {}
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'PrintSomething' not
-// using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'PrintSomething' must have an appropriate prefix followed by Pascal case as
+// required by Google Objective-C style guide
 
 void ABCBad_Name() {}
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function name 'ABCBad_Name' not
-// using function naming conventions described by Google Objective-C style guide
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function in global namespace named
+// 'ABCBad_Name' must have an appropriate prefix followed by Pascal case as
+// required by Google Objective-C style guide
 
 namespace {