clang-format: Format extern "C" blocks like namespace blocks.

namespace blocks act as if KeepEmptyLinesAtTheStartOfBlocks is always true,
and aren't collapsed to a single line even if they would fit. Do the same
for extern "C" blocks.

Before,

  extern "C" {

  void ExternCFunction();

  }

was collapsed into `extern "C" { void ExternCFunction(); }`. Now it stays like
it was.

Fixes http://crbug.com/432640 and part of PR21419.

llvm-svn: 221897

1 files changed, 24 insertions, 1 deletions

diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 37c3c0e7528..b8ab1df139b 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -187,7 +187,7 @@ TEST_F(FormatTest, RemovesEmptyLines) {
                    "\n"
                    "};"));
 
-  // Don't remove empty lines at the start of namespaces.
+  // Don't remove empty lines at the start of namespaces or extern "C" blocks.
   EXPECT_EQ("namespace N {\n"
             "\n"
             "int i;\n"
@@ -197,6 +197,29 @@ TEST_F(FormatTest, RemovesEmptyLines) {
                    "int    i;\n"
                    "}",
                    getGoogleStyle()));
+  EXPECT_EQ("extern /**/ \"C\" /**/ {\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("extern /**/ \"C\" /**/ {\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   getGoogleStyle()));
+
+  // ...but do keep inlining and removing empty lines for non-block extern "C"
+  // functions.
+  verifyFormat("extern \"C\" int f() { return 42; }", getGoogleStyle());
+  EXPECT_EQ("extern \"C\" int f() {\n"
+            "  int i = 42;\n"
+            "  return i;\n"
+            "}",
+            format("extern \"C\" int f() {\n"
+                   "\n"
+                   "  int i = 42;\n"
+                   "  return i;\n"
+                   "}",
+                   getGoogleStyle()));
 
   // Remove empty lines at the beginning and end of blocks.
   EXPECT_EQ("void f() {\n"