Index: clang/docs/ClangFormatStyleOptions.rst
===================================================================
--- clang/docs/ClangFormatStyleOptions.rst
+++ clang/docs/ClangFormatStyleOptions.rst
@@ -1611,6 +1611,9 @@
   If ``true``, clang-format adds missing namespace end comments and
   fixes invalid existing ones.
 
+  Short namespaces will not be given an end comment, unless the comment
+  is invalid in which case it is always fixed.
+
   .. code-block:: c++
 
      true:                                  false:
Index: clang/include/clang/Format/Format.h
===================================================================
--- clang/include/clang/Format/Format.h
+++ clang/include/clang/Format/Format.h
@@ -1380,6 +1380,9 @@
 
   /// If ``true``, clang-format adds missing namespace end comments and
   /// fixes invalid existing ones.
+  ///
+  /// Short namespaces will not be given an end comment, unless the comment
+  /// is invalid in which case it is always fixed.
   /// \code
   ///    true:                                  false:
   ///    namespace a {                  vs.     namespace a {
Index: clang/lib/Format/NamespaceEndCommentsFixer.cpp
===================================================================
--- clang/lib/Format/NamespaceEndCommentsFixer.cpp
+++ clang/lib/Format/NamespaceEndCommentsFixer.cpp
@@ -24,7 +24,7 @@
 namespace {
 // The maximal number of unwrapped lines that a short namespace spans.
 // Short namespaces don't need an end comment.
-static const int kShortNamespaceMaxLines = 1;
+static const int kShortNamespaceMaxLines = 0;
 
 // Computes the name of a namespace given the namespace token.
 // Returns "" for anonymous namespace.
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -211,7 +211,7 @@
   EXPECT_EQ("namespace N {\n"
             "\n"
             "int i;\n"
-            "}",
+            "}  // namespace N",
             format("namespace N {\n"
                    "\n"
                    "int    i;\n"
@@ -220,7 +220,7 @@
   EXPECT_EQ("/* something */ namespace N {\n"
             "\n"
             "int i;\n"
-            "}",
+            "}  // namespace N",
             format("/* something */ namespace N {\n"
                    "\n"
                    "int    i;\n"
@@ -229,7 +229,7 @@
   EXPECT_EQ("inline namespace N {\n"
             "\n"
             "int i;\n"
-            "}",
+            "}  // namespace N",
             format("inline namespace N {\n"
                    "\n"
                    "int    i;\n"
@@ -238,7 +238,7 @@
   EXPECT_EQ("/* something */ inline namespace N {\n"
             "\n"
             "int i;\n"
-            "}",
+            "}  // namespace N",
             format("/* something */ inline namespace N {\n"
                    "\n"
                    "int    i;\n"
@@ -247,7 +247,7 @@
   EXPECT_EQ("export namespace N {\n"
             "\n"
             "int i;\n"
-            "}",
+            "}  // namespace N",
             format("export namespace N {\n"
                    "\n"
                    "int    i;\n"
@@ -369,7 +369,7 @@
   EXPECT_EQ("namespace {\n"
             "int i;\n"
             "\n"
-            "}",
+            "} // namespace",
             format("namespace {\n"
                    "int i;\n"
                    "\n"
@@ -8887,7 +8887,7 @@
             format("void  f  (  )  {  if  ( a )  return  }"));
   EXPECT_EQ("namespace N {\n"
             "void f()\n"
-            "}",
+            "} // namespace N",
             format("namespace  N  {  void f()  }"));
   EXPECT_EQ("namespace N {\n"
             "void f() {}\n"
@@ -9839,7 +9839,7 @@
   verifyFormat("namespace Foo\n"
                "{\n"
                "void Bar();\n"
-               "};",
+               "}; // namespace Foo",
                Style);
 }
 
@@ -9872,7 +9872,7 @@
                Style);
   verifyFormat("namespace Foo {\n"
                "void Bar();\n"
-               "};",
+               "}; // namespace Foo",
                Style);
 
   Style.BreakBeforeBraces = FormatStyle::BS_Custom;
@@ -9913,7 +9913,7 @@
   verifyFormat("namespace Foo\n"
                "{\n"
                "void Bar();\n"
-               "};",
+               "}; // namespace Foo",
                Style);
 }
 
Index: clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
===================================================================
--- clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
+++ clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
@@ -142,7 +142,7 @@
   EXPECT_EQ("namespace A {\n"
             "namespace B {\n"
             "int i;\n"
-            "}\n"
+            "}// namespace B\n"
             "}// namespace A",
             fixNamespaceEndComments("namespace A {\n"
                                     "namespace B {\n"
@@ -423,8 +423,9 @@
 TEST_F(NamespaceEndCommentsFixerTest, DoesNotAddEndCommentForShortNamespace) {
   EXPECT_EQ("namespace {}", fixNamespaceEndComments("namespace {}"));
   EXPECT_EQ("namespace A {}", fixNamespaceEndComments("namespace A {}"));
-  EXPECT_EQ("namespace A { a }", fixNamespaceEndComments("namespace A { a }"));
-  EXPECT_EQ("namespace A { a };",
+  EXPECT_EQ("namespace A { a }// namespace A",
+            fixNamespaceEndComments("namespace A { a }"));
+  EXPECT_EQ("namespace A { a };// namespace A",
             fixNamespaceEndComments("namespace A { a };"));
 }