[clang-format] New flag - BraceWrapping.AfterExternBlock

Summary:
Bug: https://bugs.llvm.org/show_bug.cgi?id=34016 - **"extern C part"**

**Problem:**

Due to the lack of "brace wrapping extern" flag, clang format does parse the block after **extern** keyword moving the opening bracket to the header line always!

**Patch description:**

A new style added, new configuration flag - **BraceWrapping.AfterExternBlock** that allows us to decide whether we want a break before brace or not.

Reviewers: djasper, krasimir

Reviewed By: krasimir

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D37845

Contributed by @PriMee!

llvm-svn: 313354

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index b15e52aeb2c..40d133ff0dd 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1039,7 +1039,12 @@ void UnwrappedLineParser::parseStructuralElement() {
     if (FormatTok->Tok.is(tok::string_literal)) {
       nextToken();
       if (FormatTok->Tok.is(tok::l_brace)) {
-        parseBlock(/*MustBeDeclaration=*/true, /*AddLevel=*/false);
+        if (Style.BraceWrapping.AfterExternBlock) {
+          addUnwrappedLine();
+          parseBlock(/*MustBeDeclaration=*/true);
+        } else {
+          parseBlock(/*MustBeDeclaration=*/true, /*AddLevel=*/false);
+        }
         addUnwrappedLine();
         return;
       }