Fix the issue that not recognizing single acronym with prefix as ObjC property name.

Summary: This will make clang-tidy accept property names like xyz_URL (URL is a common acronym).

Reviewers: benhamilton, hokein

Reviewed By: benhamilton

Subscribers: jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D53955

llvm-svn: 345858
diff --git a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
index d460c6b..b772a5e 100644
--- a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
@@ -201,8 +201,7 @@
 
 void PropertyDeclarationCheck::registerMatchers(MatchFinder *Finder) {
   // this check should only be applied to ObjC sources.
-  if (!getLangOpts().ObjC)
-    return;
+  if (!getLangOpts().ObjC) return;
 
   if (IncludeDefaultAcronyms) {
     EscapedAcronyms.reserve(llvm::array_lengthof(DefaultSpecialAcronyms) +
@@ -235,9 +234,9 @@
   auto *DeclContext = MatchedDecl->getDeclContext();
   auto *CategoryDecl = llvm::dyn_cast<ObjCCategoryDecl>(DeclContext);
 
-  auto AcronymsRegex =
-      llvm::Regex("^" + AcronymsGroupRegex(EscapedAcronyms) + "$");
-  if (AcronymsRegex.match(MatchedDecl->getName())) {
+  auto SingleAcronymRegex =
+      llvm::Regex("^([a-zA-Z]+_)?" + AcronymsGroupRegex(EscapedAcronyms) + "$");
+  if (SingleAcronymRegex.match(MatchedDecl->getName())) {
     return;
   }
   if (CategoryDecl != nullptr &&