[clang-tidy/checks] Implement a clang-tidy check to verify Google Objective-C function naming conventions 📜

Summary:
§1 Description

This check finds function names in function declarations in Objective-C files that do not follow the naming pattern described in the Google Objective-C Style Guide. Function names should be in UpperCamelCase and functions that are not of static storage class should have an appropriate prefix as described in the Google Objective-C Style Guide. The function `main` is a notable exception. Function declarations in expansions in system headers are ignored.

Example conforming function definitions:
```
static bool IsPositive(int i) { return i > 0; }
static bool ABIsPositive(int i) { return i > 0; }
bool ABIsNegative(int i) { return i < 0; }
```

A fixit hint is generated for functions of static storage class but otherwise the check does not generate a fixit hint because an appropriate prefix for the function cannot be determined.

§2 Test Notes
* Verified clang-tidy tests pass successfully.
* Used check_clang_tidy.py to verify expected output of processing google-objc-function-naming.m

Reviewers: benhamilton, hokein, Wizard, aaron.ballman

Reviewed By: benhamilton

Subscribers: Eugene.Zelenko, mgorny, xazax.hun, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D51575

llvm-svn: 347132

1 files changed, 43 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h
new file mode 100644
index 00000000000..46499e90ac2
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h
@@ -0,0 +1,43 @@
+//===--- FunctionNamingCheck.h - clang-tidy ---------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_FUNCTION_NAMING_CHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_FUNCTION_NAMING_CHECK_H
+
+#include "../ClangTidy.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace clang {
+namespace tidy {
+namespace google {
+namespace objc {
+
+/// Finds function names that do not conform to the recommendations of the
+/// Google Objective-C Style Guide. Function names should be in upper camel case
+/// including capitalized acronyms and initialisms. Functions that are not of
+/// static storage class must also have an appropriate prefix. The function
+/// `main` is an exception. Note that this check does not apply to Objective-C
+/// method or property declarations.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/google-objc-function-naming.html
+class FunctionNamingCheck : public ClangTidyCheck {
+public:
+  FunctionNamingCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace objc
+} // namespace google
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_FUNCTION_NAMING_CHECK_H