Add new check in google module for Objective-C code to ensure global variables follow the naming convention of Google Objective-C Style Guide

Summary:
This is a new checker for objc files in clang-tidy.

The new check finds global variable declarations in Objective-C files that are not follow the pattern of variable names in Google's Objective-C Style Guide.

All the global variables should follow the pattern of "g[A-Z].*" (variables) or "k[A-Z].*" (constants). The check will suggest a variable name that follows the pattern
if it can be inferred from the original name.

Patch by Yan Zhang!

Reviewers: benhamilton, hokein, alexfh

Reviewed By: hokein

Subscribers: Eugene.Zelenko, mgorny

Differential Revision: https://reviews.llvm.org/D39391

llvm-svn: 317552

1 files changed, 42 insertions, 0 deletions

diff --git a/clang-tools-extra/docs/clang-tidy/checks/google-objc-global-variable-declaration.rst b/clang-tools-extra/docs/clang-tidy/checks/google-objc-global-variable-declaration.rst
new file mode 100644
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+++ b/clang-tools-extra/docs/clang-tidy/checks/google-objc-global-variable-declaration.rst
@@ -0,0 +1,42 @@
+.. title:: clang-tidy - google-objc-global-variable-declaration
+
+google-objc-global-variable-declaration
+=======================================
+
+Finds global variable declarations in Objective-C files that are not follow the pattern
+of variable names in Google's Objective-C Style Guide.
+
+The corresponding style guide rule:
+http://google.github.io/styleguide/objcguide.html#variable-names
+
+All the global variables should follow the pattern of `g[A-Z].*` (variables) or
+`k[A-Z].*` (constants). The check will suggest a variable name that follows the pattern
+if it can be inferred from the original name.
+
+For code:
+
+.. code-block:: objc
+  static NSString* myString = @"hello";
+
+The fix will be:
+
+.. code-block:: objc
+  static NSString* gMyString = @"hello";
+
+Another example of constant:
+
+.. code-block:: objc
+  static NSString* const myConstString = @"hello";
+
+The fix will be:
+
+.. code-block:: objc
+  static NSString* const kMyConstString = @"hello";
+
+However for code that prefixed with non-alphabetical characters like:
+
+.. code-block:: objc
+  static NSString* __anotherString = @"world";
+
+The check will give a warning message but will not be able to suggest a fix. The user
+need to fix it on his own.