[clang] clang-format: Add "AllowShortNamespacesOnASingleLine" option (PR #105597)

Galen Elias via cfe-commits cfe-commits at lists.llvm.org
Fri Nov 8 15:20:52 PST 2024


https://github.com/galenelias updated https://github.com/llvm/llvm-project/pull/105597

>From 4118b7dde9adbee7b6aaf5d094d34cb6b64f6c77 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Wed, 21 Aug 2024 16:33:42 -0700
Subject: [PATCH 01/12] clang-format: Add "AllowShortNamespacesOnASingleLine"
 option

This addresses: https://github.com/llvm/llvm-project/issues/101363
which is a resurrection of a previously opened but never completed
review: https://reviews.llvm.org/D11851

The feature is to allow code like the following not to be broken across
multiple lines:

```
namespace foo { class bar; }
namespace foo { namespace bar { class baz; } }
```

Code like this is commonly used for forward declarations, which are
ideally kept compact. This is also apparently the format that
include-what-you-use will insert for forward declarations.
---
 clang/include/clang/Format/Format.h         |   5 +
 clang/lib/Format/Format.cpp                 |   3 +
 clang/lib/Format/UnwrappedLineFormatter.cpp |  82 ++++++++++++++
 clang/unittests/Format/FormatTest.cpp       | 112 ++++++++++++++++++++
 4 files changed, 202 insertions(+)

diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index 2af1d4065c3cc1..c96fc4d1d9557b 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -972,6 +972,11 @@ struct FormatStyle {
   /// \version 3.7
   bool AllowShortLoopsOnASingleLine;
 
+  /// If ``true``, ``namespace a { class b; }`` can be put on a single a single
+  /// line.
+  /// \version 19
+  bool AllowShortNamespacesOnASingleLine;
+
   /// Different ways to break after the function definition return type.
   /// This option is **deprecated** and is retained for backwards compatibility.
   enum DefinitionReturnTypeBreakingStyle : int8_t {
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 97fac41cdd3008..495b727e609df6 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -952,6 +952,8 @@ template <> struct MappingTraits<FormatStyle> {
                    Style.AllowShortLambdasOnASingleLine);
     IO.mapOptional("AllowShortLoopsOnASingleLine",
                    Style.AllowShortLoopsOnASingleLine);
+    IO.mapOptional("AllowShortNamespacesOnASingleLine",
+                   Style.AllowShortNamespacesOnASingleLine);
     IO.mapOptional("AlwaysBreakAfterDefinitionReturnType",
                    Style.AlwaysBreakAfterDefinitionReturnType);
     IO.mapOptional("AlwaysBreakBeforeMultilineStrings",
@@ -1457,6 +1459,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Never;
   LLVMStyle.AllowShortLambdasOnASingleLine = FormatStyle::SLS_All;
   LLVMStyle.AllowShortLoopsOnASingleLine = false;
+  LLVMStyle.AllowShortNamespacesOnASingleLine = false;
   LLVMStyle.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_None;
   LLVMStyle.AlwaysBreakBeforeMultilineStrings = false;
   LLVMStyle.AttributeMacros.push_back("__capability");
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 1804c1437fd41d..971eac1978bb71 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -420,6 +420,15 @@ class LineJoiner {
         TheLine->First != LastNonComment) {
       return MergeShortFunctions ? tryMergeSimpleBlock(I, E, Limit) : 0;
     }
+
+    if (TheLine->Last->is(tok::l_brace)) {
+      if (Style.AllowShortNamespacesOnASingleLine &&
+          TheLine->First->is(tok::kw_namespace)) {
+        if (unsigned result = tryMergeNamespace(I, E, Limit))
+          return result;
+      }
+    }
+
     // Try to merge a control statement block with left brace unwrapped.
     if (TheLine->Last->is(tok::l_brace) && FirstNonComment != TheLine->Last &&
         FirstNonComment->isOneOf(tok::kw_if, tok::kw_while, tok::kw_for,
@@ -616,6 +625,62 @@ class LineJoiner {
     return 1;
   }
 
+  unsigned tryMergeNamespace(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
+                             SmallVectorImpl<AnnotatedLine *>::const_iterator E,
+                             unsigned Limit) {
+    if (Limit == 0)
+      return 0;
+    if (I[1]->InPPDirective != (*I)->InPPDirective ||
+        (I[1]->InPPDirective && I[1]->First->HasUnescapedNewline)) {
+      return 0;
+    }
+    if (I + 2 == E || I[2]->Type == LT_Invalid)
+      return 0;
+
+    Limit = limitConsideringMacros(I + 1, E, Limit);
+
+    if (!nextTwoLinesFitInto(I, Limit))
+      return 0;
+
+    // Check if it's a namespace inside a namespace, and call recursively if so
+    // '3' is the sizes of the whitespace and closing brace for " _inner_ }"
+    if (I[1]->First->is(tok::kw_namespace)) {
+      if (I[1]->Last->is(TT_LineComment))
+        return 0;
+
+      unsigned inner_limit = Limit - I[1]->Last->TotalLength - 3;
+      unsigned inner_result = tryMergeNamespace(I + 1, E, inner_limit);
+      if (!inner_result)
+        return 0;
+      // check if there is even a line after the inner result
+      if (I + 2 + inner_result >= E)
+        return 0;
+      // check that the line after the inner result starts with a closing brace
+      // which we are permitted to merge into one line
+      if (I[2 + inner_result]->First->is(tok::r_brace) &&
+          !I[2 + inner_result]->First->MustBreakBefore &&
+          !I[1 + inner_result]->Last->is(TT_LineComment) &&
+          nextNLinesFitInto(I, I + 2 + inner_result + 1, Limit)) {
+        return 2 + inner_result;
+      }
+      return 0;
+    }
+
+    // There's no inner namespace, so we are considering to merge at most one
+    // line.
+
+    // The line which is in the namespace should end with semicolon
+    if (I[1]->Last->isNot(tok::semi))
+      return 0;
+
+    // Last, check that the third line starts with a closing brace.
+    if (I[2]->First->isNot(tok::r_brace) || I[2]->First->MustBreakBefore)
+      return 0;
+
+    // If so, merge all three lines.
+    return 2;
+  }
+
   unsigned tryMergeSimpleControlStatement(
       SmallVectorImpl<AnnotatedLine *>::const_iterator I,
       SmallVectorImpl<AnnotatedLine *>::const_iterator E, unsigned Limit) {
@@ -916,6 +981,23 @@ class LineJoiner {
     return 1 + I[1]->Last->TotalLength + 1 + I[2]->Last->TotalLength <= Limit;
   }
 
+  bool nextNLinesFitInto(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
+                         SmallVectorImpl<AnnotatedLine *>::const_iterator E,
+                         unsigned Limit) {
+    unsigned joinedLength = 0;
+    for (SmallVectorImpl<AnnotatedLine *>::const_iterator J = I + 1; J != E;
+         ++J) {
+
+      if ((*J)->First->MustBreakBefore)
+        return false;
+
+      joinedLength += 1 + (*J)->Last->TotalLength;
+      if (joinedLength > Limit)
+        return false;
+    }
+    return true;
+  }
+
   bool containsMustBreak(const AnnotatedLine *Line) {
     assert(Line->First);
     // Ignore the first token, because in this situation, it applies more to the
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 794ccab3704534..468cb6b98dd745 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -27981,6 +27981,118 @@ TEST_F(FormatTest, BreakBinaryOperations) {
                Style);
 }
 
+TEST_F(FormatTest, ShortNamespacesOption) {
+  FormatStyle style = getLLVMStyle();
+  style.AllowShortNamespacesOnASingleLine = true;
+  style.FixNamespaceComments = false;
+
+  // Basic functionality
+  verifyFormat("namespace foo { class bar; }", style);
+  verifyFormat("namespace foo::bar { class baz; }", style);
+  verifyFormat("namespace { class bar; }", style);
+  verifyFormat("namespace foo {\n"
+               "class bar;\n"
+               "class baz;\n"
+               "}",
+               style);
+
+  // Trailing comments prevent merging
+  verifyFormat("namespace foo {\n"
+               "namespace baz { class qux; } // comment\n"
+               "}",
+               style);
+
+  // Make sure code doesn't walk to far on unbalanced code
+  verifyFormat("namespace foo {", style);
+  verifyFormat("namespace foo {\n"
+               "class baz;",
+               style);
+  verifyFormat("namespace foo {\n"
+               "namespace bar { class baz; }",
+               style);
+
+  // Nested namespaces
+  verifyFormat("namespace foo { namespace bar { class baz; } }", style);
+  verifyFormat("namespace foo {\n"
+               "namespace bar { class baz; }\n"
+               "namespace quar { class quaz; }\n"
+               "}",
+               style);
+
+  // Varying inner content
+  verifyFormat("namespace foo {\n"
+               "int f() { return 5; }\n"
+               "}",
+               style);
+  verifyFormat("namespace foo { template <T> struct bar; }", style);
+  verifyFormat("namespace foo { constexpr int num = 42; }", style);
+
+  // Validate wrapping scenarios around the ColumnLimit
+  style.ColumnLimit = 64;
+
+  // Validate just under the ColumnLimit
+  verifyFormat(
+      "namespace foo { namespace bar { namespace baz { class qux; } } }",
+      style);
+
+  // Validate just over the ColumnLimit
+  verifyFormat("namespace foo {\n"
+               "namespace bar { namespace baz { class quux; } }\n"
+               "}",
+               style);
+
+  verifyFormat("namespace foo {\n"
+               "namespace bar {\n"
+               "namespace baz { namespace qux { class quux; } }\n"
+               "}\n"
+               "}",
+               style);
+
+  // Validate that the ColumnLimit logic accounts for trailing content as well
+  verifyFormat("namespace foo {\n"
+               "namespace bar { namespace baz { class qux; } }\n"
+               "} // extra",
+               style);
+
+  // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
+  // instances alone
+  style.ColumnLimit = 0;
+  verifyFormat("namespace foo { namespace bar { namespace baz { namespace qux "
+               "{ class quux; } } } }",
+               style);
+
+  verifyNoChange("namespace foo {\n"
+                 "namespace bar {\n"
+                 "namespace baz { namespace qux { class quux; } }\n"
+                 "}\n"
+                 "}",
+                 style);
+
+  // This option doesn't really work with FixNamespaceComments and nested
+  // namespaces. Code should use the concatenated namespace syntax.  e.g.
+  // 'namespace foo::bar'
+  style.FixNamespaceComments = true;
+
+  verifyFormat(
+      "namespace foo {\n"
+      "namespace bar { namespace baz { class qux; } } // namespace bar\n"
+      "} // namespace foo",
+      "namespace foo { namespace bar { namespace baz { class qux; } } }",
+      style);
+
+  // This option doesn't really make any sense with ShortNamespaceLines = 0
+  style.ShortNamespaceLines = 0;
+
+  verifyFormat(
+      "namespace foo {\n"
+      "namespace bar {\n"
+      "namespace baz { class qux; } // namespace baz\n"
+      "} // namespace bar\n"
+      "} // namespace foo",
+      "namespace foo { namespace bar { namespace baz { class qux; } } }",
+      style);
+}
+
 } // namespace
 } // namespace test
 } // namespace format

>From 86534c3ba6a82e2782a6bf96350e1e71fa633f63 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Thu, 22 Aug 2024 09:16:32 -0700
Subject: [PATCH 02/12] Use PascalCase for local variable names

---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 18 +++----
 clang/unittests/Format/FormatTest.cpp       | 56 ++++++++++-----------
 2 files changed, 37 insertions(+), 37 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 971eac1978bb71..ddb94c62d0da2c 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -648,20 +648,20 @@ class LineJoiner {
       if (I[1]->Last->is(TT_LineComment))
         return 0;
 
-      unsigned inner_limit = Limit - I[1]->Last->TotalLength - 3;
-      unsigned inner_result = tryMergeNamespace(I + 1, E, inner_limit);
-      if (!inner_result)
+      const unsigned InnerLimit = Limit - I[1]->Last->TotalLength - 3;
+      const unsigned MergedLines = tryMergeNamespace(I + 1, E, InnerLimit);
+      if (!MergedLines)
         return 0;
       // check if there is even a line after the inner result
-      if (I + 2 + inner_result >= E)
+      if (I + 2 + MergedLines >= E)
         return 0;
       // check that the line after the inner result starts with a closing brace
       // which we are permitted to merge into one line
-      if (I[2 + inner_result]->First->is(tok::r_brace) &&
-          !I[2 + inner_result]->First->MustBreakBefore &&
-          !I[1 + inner_result]->Last->is(TT_LineComment) &&
-          nextNLinesFitInto(I, I + 2 + inner_result + 1, Limit)) {
-        return 2 + inner_result;
+      if (I[2 + MergedLines]->First->is(tok::r_brace) &&
+          !I[2 + MergedLines]->First->MustBreakBefore &&
+          !I[1 + MergedLines]->Last->is(TT_LineComment) &&
+          nextNLinesFitInto(I, I + 2 + MergedLines + 1, Limit)) {
+        return 2 + MergedLines;
       }
       return 0;
     }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 468cb6b98dd745..0fb1ed2d47e31d 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -27982,106 +27982,106 @@ TEST_F(FormatTest, BreakBinaryOperations) {
 }
 
 TEST_F(FormatTest, ShortNamespacesOption) {
-  FormatStyle style = getLLVMStyle();
-  style.AllowShortNamespacesOnASingleLine = true;
-  style.FixNamespaceComments = false;
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortNamespacesOnASingleLine = true;
+  Style.FixNamespaceComments = false;
 
   // Basic functionality
-  verifyFormat("namespace foo { class bar; }", style);
-  verifyFormat("namespace foo::bar { class baz; }", style);
-  verifyFormat("namespace { class bar; }", style);
+  verifyFormat("namespace foo { class bar; }", Style);
+  verifyFormat("namespace foo::bar { class baz; }", Style);
+  verifyFormat("namespace { class bar; }", Style);
   verifyFormat("namespace foo {\n"
                "class bar;\n"
                "class baz;\n"
                "}",
-               style);
+               Style);
 
   // Trailing comments prevent merging
   verifyFormat("namespace foo {\n"
                "namespace baz { class qux; } // comment\n"
                "}",
-               style);
+               Style);
 
   // Make sure code doesn't walk to far on unbalanced code
-  verifyFormat("namespace foo {", style);
+  verifyFormat("namespace foo {", Style);
   verifyFormat("namespace foo {\n"
                "class baz;",
-               style);
+               Style);
   verifyFormat("namespace foo {\n"
                "namespace bar { class baz; }",
-               style);
+               Style);
 
   // Nested namespaces
-  verifyFormat("namespace foo { namespace bar { class baz; } }", style);
+  verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
   verifyFormat("namespace foo {\n"
                "namespace bar { class baz; }\n"
                "namespace quar { class quaz; }\n"
                "}",
-               style);
+               Style);
 
   // Varying inner content
   verifyFormat("namespace foo {\n"
                "int f() { return 5; }\n"
                "}",
-               style);
-  verifyFormat("namespace foo { template <T> struct bar; }", style);
-  verifyFormat("namespace foo { constexpr int num = 42; }", style);
+               Style);
+  verifyFormat("namespace foo { template <T> struct bar; }", Style);
+  verifyFormat("namespace foo { constexpr int num = 42; }", Style);
 
   // Validate wrapping scenarios around the ColumnLimit
-  style.ColumnLimit = 64;
+  Style.ColumnLimit = 64;
 
   // Validate just under the ColumnLimit
   verifyFormat(
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
-      style);
+      Style);
 
   // Validate just over the ColumnLimit
   verifyFormat("namespace foo {\n"
                "namespace bar { namespace baz { class quux; } }\n"
                "}",
-               style);
+               Style);
 
   verifyFormat("namespace foo {\n"
                "namespace bar {\n"
                "namespace baz { namespace qux { class quux; } }\n"
                "}\n"
                "}",
-               style);
+               Style);
 
   // Validate that the ColumnLimit logic accounts for trailing content as well
   verifyFormat("namespace foo {\n"
                "namespace bar { namespace baz { class qux; } }\n"
                "} // extra",
-               style);
+               Style);
 
   // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
   // instances alone
-  style.ColumnLimit = 0;
+  Style.ColumnLimit = 0;
   verifyFormat("namespace foo { namespace bar { namespace baz { namespace qux "
                "{ class quux; } } } }",
-               style);
+               Style);
 
   verifyNoChange("namespace foo {\n"
                  "namespace bar {\n"
                  "namespace baz { namespace qux { class quux; } }\n"
                  "}\n"
                  "}",
-                 style);
+                 Style);
 
   // This option doesn't really work with FixNamespaceComments and nested
   // namespaces. Code should use the concatenated namespace syntax.  e.g.
   // 'namespace foo::bar'
-  style.FixNamespaceComments = true;
+  Style.FixNamespaceComments = true;
 
   verifyFormat(
       "namespace foo {\n"
       "namespace bar { namespace baz { class qux; } } // namespace bar\n"
       "} // namespace foo",
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
-      style);
+      Style);
 
   // This option doesn't really make any sense with ShortNamespaceLines = 0
-  style.ShortNamespaceLines = 0;
+  Style.ShortNamespaceLines = 0;
 
   verifyFormat(
       "namespace foo {\n"
@@ -28090,7 +28090,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
       "} // namespace bar\n"
       "} // namespace foo",
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
-      style);
+      Style);
 }
 
 } // namespace

>From 2159b8c222b9e9c8e2fdf60211a171e0a58b58b1 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Wed, 28 Aug 2024 10:42:05 -0700
Subject: [PATCH 03/12] Address review comments

---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 22 +++++++++----------
 clang/unittests/Format/FormatTest.cpp       | 24 ++++++++++-----------
 2 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index ddb94c62d0da2c..31bf3f484c4c39 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -643,7 +643,7 @@ class LineJoiner {
       return 0;
 
     // Check if it's a namespace inside a namespace, and call recursively if so
-    // '3' is the sizes of the whitespace and closing brace for " _inner_ }"
+    // '3' is the sizes of the whitespace and closing brace for " _inner_ }".
     if (I[1]->First->is(tok::kw_namespace)) {
       if (I[1]->Last->is(TT_LineComment))
         return 0;
@@ -652,11 +652,11 @@ class LineJoiner {
       const unsigned MergedLines = tryMergeNamespace(I + 1, E, InnerLimit);
       if (!MergedLines)
         return 0;
-      // check if there is even a line after the inner result
-      if (I + 2 + MergedLines >= E)
+      // Check if there is even a line after the inner result.
+      if (std::distance(I, E) <= MergedLines + 2)
         return 0;
-      // check that the line after the inner result starts with a closing brace
-      // which we are permitted to merge into one line
+      // Check that the line after the inner result starts with a closing brace
+      // which we are permitted to merge into one line.
       if (I[2 + MergedLines]->First->is(tok::r_brace) &&
           !I[2 + MergedLines]->First->MustBreakBefore &&
           !I[1 + MergedLines]->Last->is(TT_LineComment) &&
@@ -669,7 +669,7 @@ class LineJoiner {
     // There's no inner namespace, so we are considering to merge at most one
     // line.
 
-    // The line which is in the namespace should end with semicolon
+    // The line which is in the namespace should end with semicolon.
     if (I[1]->Last->isNot(tok::semi))
       return 0;
 
@@ -984,15 +984,13 @@ class LineJoiner {
   bool nextNLinesFitInto(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
                          SmallVectorImpl<AnnotatedLine *>::const_iterator E,
                          unsigned Limit) {
-    unsigned joinedLength = 0;
-    for (SmallVectorImpl<AnnotatedLine *>::const_iterator J = I + 1; J != E;
-         ++J) {
-
+    unsigned JoinedLength = 0;
+    for (auto J = I + 1; J != E; ++J) {
       if ((*J)->First->MustBreakBefore)
         return false;
 
-      joinedLength += 1 + (*J)->Last->TotalLength;
-      if (joinedLength > Limit)
+      JoinedLength += 1 + (*J)->Last->TotalLength;
+      if (JoinedLength > Limit)
         return false;
     }
     return true;
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 0fb1ed2d47e31d..e03e0a871c8d19 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -27986,7 +27986,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   Style.AllowShortNamespacesOnASingleLine = true;
   Style.FixNamespaceComments = false;
 
-  // Basic functionality
+  // Basic functionality.
   verifyFormat("namespace foo { class bar; }", Style);
   verifyFormat("namespace foo::bar { class baz; }", Style);
   verifyFormat("namespace { class bar; }", Style);
@@ -27996,13 +27996,13 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "}",
                Style);
 
-  // Trailing comments prevent merging
+  // Trailing comments prevent merging.
   verifyFormat("namespace foo {\n"
                "namespace baz { class qux; } // comment\n"
                "}",
                Style);
 
-  // Make sure code doesn't walk to far on unbalanced code
+  // Make sure code doesn't walk to far on unbalanced code.
   verifyFormat("namespace foo {", Style);
   verifyFormat("namespace foo {\n"
                "class baz;",
@@ -28011,7 +28011,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "namespace bar { class baz; }",
                Style);
 
-  // Nested namespaces
+  // Nested namespaces.
   verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
   verifyFormat("namespace foo {\n"
                "namespace bar { class baz; }\n"
@@ -28019,7 +28019,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "}",
                Style);
 
-  // Varying inner content
+  // Varying inner content.
   verifyFormat("namespace foo {\n"
                "int f() { return 5; }\n"
                "}",
@@ -28027,15 +28027,15 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   verifyFormat("namespace foo { template <T> struct bar; }", Style);
   verifyFormat("namespace foo { constexpr int num = 42; }", Style);
 
-  // Validate wrapping scenarios around the ColumnLimit
+  // Validate wrapping scenarios around the ColumnLimit.
   Style.ColumnLimit = 64;
 
-  // Validate just under the ColumnLimit
+  // Validate just under the ColumnLimit.
   verifyFormat(
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
       Style);
 
-  // Validate just over the ColumnLimit
+  // Validate just over the ColumnLimit.
   verifyFormat("namespace foo {\n"
                "namespace bar { namespace baz { class quux; } }\n"
                "}",
@@ -28048,14 +28048,14 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "}",
                Style);
 
-  // Validate that the ColumnLimit logic accounts for trailing content as well
+  // Validate that the ColumnLimit logic accounts for trailing content as well.
   verifyFormat("namespace foo {\n"
                "namespace bar { namespace baz { class qux; } }\n"
                "} // extra",
                Style);
 
   // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
-  // instances alone
+  // instances alone.
   Style.ColumnLimit = 0;
   verifyFormat("namespace foo { namespace bar { namespace baz { namespace qux "
                "{ class quux; } } } }",
@@ -28070,7 +28070,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
 
   // This option doesn't really work with FixNamespaceComments and nested
   // namespaces. Code should use the concatenated namespace syntax.  e.g.
-  // 'namespace foo::bar'
+  // 'namespace foo::bar'.
   Style.FixNamespaceComments = true;
 
   verifyFormat(
@@ -28080,7 +28080,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
       Style);
 
-  // This option doesn't really make any sense with ShortNamespaceLines = 0
+  // This option doesn't really make any sense with ShortNamespaceLines = 0.
   Style.ShortNamespaceLines = 0;
 
   verifyFormat(

>From 07ec70d700bd061c5ccb7803d22e96a887734895 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Thu, 5 Sep 2024 07:41:49 -0700
Subject: [PATCH 04/12] Switch version of new format option to 20

---
 clang/include/clang/Format/Format.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index c96fc4d1d9557b..e1d10e64c92fe0 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -974,7 +974,7 @@ struct FormatStyle {
 
   /// If ``true``, ``namespace a { class b; }`` can be put on a single a single
   /// line.
-  /// \version 19
+  /// \version 20
   bool AllowShortNamespacesOnASingleLine;
 
   /// Different ways to break after the function definition return type.

>From b5f727b25352823e40d1c07723e5f0312c4c53f9 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Tue, 10 Sep 2024 08:30:37 -0700
Subject: [PATCH 05/12] Re-generate StylClangFormatStyleOptions.rst

---
 clang/docs/ClangFormatStyleOptions.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index c79a635d86a6ef..53c3d26fe1d96a 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -1976,6 +1976,12 @@ the configuration (without a prefix: ``Auto``).
   If ``true``, ``while (true) continue;`` can be put on a single
   line.
 
+.. _AllowShortNamespacesOnASingleLine:
+
+**AllowShortNamespacesOnASingleLine** (``Boolean``) :versionbadge:`clang-format 20` :ref:`¶ <AllowShortNamespacesOnASingleLine>`
+  If ``true``, ``namespace a { class b; }`` can be put on a single a single
+  line.
+
 .. _AlwaysBreakAfterDefinitionReturnType:
 
 **AlwaysBreakAfterDefinitionReturnType** (``DefinitionReturnTypeBreakingStyle``) :versionbadge:`clang-format 3.7` :ref:`¶ <AlwaysBreakAfterDefinitionReturnType>`

>From 986d2d54cacf9fed5b2706ea180dfbdc34153a35 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Tue, 10 Sep 2024 08:31:06 -0700
Subject: [PATCH 06/12] Add ConfigParseTest

---
 clang/unittests/Format/ConfigParseTest.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index 2ee0df99353ff5..37edaa5fd9c128 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/clang/unittests/Format/ConfigParseTest.cpp
@@ -159,6 +159,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(AllowShortCompoundRequirementOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortEnumsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortLoopsOnASingleLine);
+  CHECK_PARSE_BOOL(AllowShortNamespacesOnASingleLine);
   CHECK_PARSE_BOOL(BinPackArguments);
   CHECK_PARSE_BOOL(BinPackParameters);
   CHECK_PARSE_BOOL(BreakAdjacentStringLiterals);

>From 40a85d1d0730e684cabefffb4a4356ea104ccfda Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Tue, 10 Sep 2024 08:31:21 -0700
Subject: [PATCH 07/12] Fix interaction with CompactNamespaces

---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 17 +++++-----
 clang/unittests/Format/FormatTest.cpp       | 36 ++++++++++++++-------
 2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 31bf3f484c4c39..756278b4e8ddf4 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -361,9 +361,18 @@ class LineJoiner {
     const auto *FirstNonComment = TheLine->getFirstNonComment();
     if (!FirstNonComment)
       return 0;
+
     // FIXME: There are probably cases where we should use FirstNonComment
     // instead of TheLine->First.
 
+    if (TheLine->Last->is(tok::l_brace)) {
+      if (Style.AllowShortNamespacesOnASingleLine &&
+          TheLine->First->is(tok::kw_namespace)) {
+        if (unsigned result = tryMergeNamespace(I, E, Limit))
+          return result;
+      }
+    }
+
     if (Style.CompactNamespaces) {
       if (const auto *NSToken = TheLine->First->getNamespaceToken()) {
         int J = 1;
@@ -421,14 +430,6 @@ class LineJoiner {
       return MergeShortFunctions ? tryMergeSimpleBlock(I, E, Limit) : 0;
     }
 
-    if (TheLine->Last->is(tok::l_brace)) {
-      if (Style.AllowShortNamespacesOnASingleLine &&
-          TheLine->First->is(tok::kw_namespace)) {
-        if (unsigned result = tryMergeNamespace(I, E, Limit))
-          return result;
-      }
-    }
-
     // Try to merge a control statement block with left brace unwrapped.
     if (TheLine->Last->is(tok::l_brace) && FirstNonComment != TheLine->Last &&
         FirstNonComment->isOneOf(tok::kw_if, tok::kw_while, tok::kw_for,
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index e03e0a871c8d19..0dd38b8b3d4692 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -27982,9 +27982,11 @@ TEST_F(FormatTest, BreakBinaryOperations) {
 }
 
 TEST_F(FormatTest, ShortNamespacesOption) {
-  FormatStyle Style = getLLVMStyle();
-  Style.AllowShortNamespacesOnASingleLine = true;
-  Style.FixNamespaceComments = false;
+  auto BaseStyle = getLLVMStyle();
+  BaseStyle.AllowShortNamespacesOnASingleLine = true;
+  BaseStyle.FixNamespaceComments = false;
+
+  auto Style = BaseStyle;
 
   // Basic functionality.
   verifyFormat("namespace foo { class bar; }", Style);
@@ -28002,7 +28004,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "}",
                Style);
 
-  // Make sure code doesn't walk to far on unbalanced code.
+  // Make sure code doesn't walk too far on unbalanced code.
   verifyFormat("namespace foo {", Style);
   verifyFormat("namespace foo {\n"
                "class baz;",
@@ -28015,7 +28017,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
   verifyFormat("namespace foo {\n"
                "namespace bar { class baz; }\n"
-               "namespace quar { class quaz; }\n"
+               "namespace qux { class quux; }\n"
                "}",
                Style);
 
@@ -28057,20 +28059,32 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
   // instances alone.
   Style.ColumnLimit = 0;
-  verifyFormat("namespace foo { namespace bar { namespace baz { namespace qux "
-               "{ class quux; } } } }",
-               Style);
+  verifyFormat(
+      "namespace foo { namespace bar { namespace baz { class qux; } } }",
+      Style);
 
   verifyNoChange("namespace foo {\n"
-                 "namespace bar {\n"
-                 "namespace baz { namespace qux { class quux; } }\n"
-                 "}\n"
+                 "namespace bar { namespace baz { class qux; } }\n"
                  "}",
                  Style);
 
+  Style = BaseStyle;
+  Style.CompactNamespaces = true;
+  verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
+
+  // If we can't merge an outer nested namespaces, but can merge an inner
+  // nested namespace, then CompactNamespaces will merge the outer namespace
+  // first, preventing the merging of the inner namespace
+  verifyFormat("namespace foo { namespace baz {\n"
+               "class qux;\n"
+               "} // comment\n"
+               "}",
+               Style);
+
   // This option doesn't really work with FixNamespaceComments and nested
   // namespaces. Code should use the concatenated namespace syntax.  e.g.
   // 'namespace foo::bar'.
+  Style = BaseStyle;
   Style.FixNamespaceComments = true;
 
   verifyFormat(

>From ad1fdbb0131b10acf213b7fe49b0421856eadbc8 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Wed, 25 Sep 2024 16:20:46 -0700
Subject: [PATCH 08/12] Address additional PR comments

---
 clang/include/clang/Format/Format.h         |  3 +--
 clang/lib/Format/UnwrappedLineFormatter.cpp | 20 +++++++++++---------
 clang/unittests/Format/FormatTest.cpp       |  2 +-
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index e1d10e64c92fe0..f09cfc90f7a4c1 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -972,8 +972,7 @@ struct FormatStyle {
   /// \version 3.7
   bool AllowShortLoopsOnASingleLine;
 
-  /// If ``true``, ``namespace a { class b; }`` can be put on a single a single
-  /// line.
+  /// If ``true``, ``namespace a { class b; }`` can be put on a single line.
   /// \version 20
   bool AllowShortNamespacesOnASingleLine;
 
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 756278b4e8ddf4..6b57f8005688e9 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -368,7 +368,8 @@ class LineJoiner {
     if (TheLine->Last->is(tok::l_brace)) {
       if (Style.AllowShortNamespacesOnASingleLine &&
           TheLine->First->is(tok::kw_namespace)) {
-        if (unsigned result = tryMergeNamespace(I, E, Limit))
+        unsigned result = tryMergeNamespace(I, E, Limit);
+        if (result > 0)
           return result;
       }
     }
@@ -643,26 +644,27 @@ class LineJoiner {
     if (!nextTwoLinesFitInto(I, Limit))
       return 0;
 
-    // Check if it's a namespace inside a namespace, and call recursively if so
+    // Check if it's a namespace inside a namespace, and call recursively if so.
     // '3' is the sizes of the whitespace and closing brace for " _inner_ }".
     if (I[1]->First->is(tok::kw_namespace)) {
-      if (I[1]->Last->is(TT_LineComment))
+      if (I[1]->Last->is(tok::comment))
         return 0;
 
       const unsigned InnerLimit = Limit - I[1]->Last->TotalLength - 3;
       const unsigned MergedLines = tryMergeNamespace(I + 1, E, InnerLimit);
       if (!MergedLines)
         return 0;
+      const auto N = MergedLines + 2;
       // Check if there is even a line after the inner result.
-      if (std::distance(I, E) <= MergedLines + 2)
+      if (std::distance(I, E) <= N)
         return 0;
       // Check that the line after the inner result starts with a closing brace
       // which we are permitted to merge into one line.
-      if (I[2 + MergedLines]->First->is(tok::r_brace) &&
-          !I[2 + MergedLines]->First->MustBreakBefore &&
-          !I[1 + MergedLines]->Last->is(TT_LineComment) &&
-          nextNLinesFitInto(I, I + 2 + MergedLines + 1, Limit)) {
-        return 2 + MergedLines;
+      if (I[N]->First->is(tok::r_brace) &&
+          !I[N]->First->MustBreakBefore &&
+          !I[MergedLines + 1]->Last->is(tok::comment) &&
+          nextNLinesFitInto(I, I + N + 1, Limit)) {
+        return N;
       }
       return 0;
     }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 0dd38b8b3d4692..434f0a0dfb6079 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -28074,7 +28074,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
 
   // If we can't merge an outer nested namespaces, but can merge an inner
   // nested namespace, then CompactNamespaces will merge the outer namespace
-  // first, preventing the merging of the inner namespace
+  // first, preventing the merging of the inner namespace.
   verifyFormat("namespace foo { namespace baz {\n"
                "class qux;\n"
                "} // comment\n"

>From b8a21f7843f496e697abc69f8e3cfae90a995d2d Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Thu, 26 Sep 2024 08:15:02 -0700
Subject: [PATCH 09/12] clang-format run

---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 6b57f8005688e9..300bd770f993da 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -660,8 +660,7 @@ class LineJoiner {
         return 0;
       // Check that the line after the inner result starts with a closing brace
       // which we are permitted to merge into one line.
-      if (I[N]->First->is(tok::r_brace) &&
-          !I[N]->First->MustBreakBefore &&
+      if (I[N]->First->is(tok::r_brace) && !I[N]->First->MustBreakBefore &&
           !I[MergedLines + 1]->Last->is(tok::comment) &&
           nextNLinesFitInto(I, I + N + 1, Limit)) {
         return N;

>From e735f46f15ce62d7c63a9ad287025409208b8483 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Tue, 15 Oct 2024 14:59:50 -0700
Subject: [PATCH 10/12] Re-work interaction with 'CompactNamespaces' option

- Disable recursive merging of nested namespaces onto a single line
  unless 'CompactNamespaces' is enabled.

- Fix off-by-one error in CompactNamespaces code. For nested namespaces
  with 3 or more namespaces, it was incorrectly compacting lines which
  were 1 or two spaces over the ColumnLimit, leading to incorrect
  formatting results.

- Add release notes mention.

- Re-generate Style Options documentation
---
 clang/docs/ClangFormatStyleOptions.rst      |  3 +-
 clang/docs/ReleaseNotes.rst                 |  2 +
 clang/lib/Format/UnwrappedLineFormatter.cpp |  7 +-
 clang/unittests/Format/FormatTest.cpp       | 98 +++++++++++----------
 4 files changed, 60 insertions(+), 50 deletions(-)

diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index 53c3d26fe1d96a..317fc99b498f8f 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -1979,8 +1979,7 @@ the configuration (without a prefix: ``Auto``).
 .. _AllowShortNamespacesOnASingleLine:
 
 **AllowShortNamespacesOnASingleLine** (``Boolean``) :versionbadge:`clang-format 20` :ref:`¶ <AllowShortNamespacesOnASingleLine>`
-  If ``true``, ``namespace a { class b; }`` can be put on a single a single
-  line.
+  If ``true``, ``namespace a { class b; }`` can be put on a single line.
 
 .. _AlwaysBreakAfterDefinitionReturnType:
 
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 5c156a9c073a9c..f139a196cf4941 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -410,6 +410,8 @@ clang-format
 
 - Adds ``BreakBinaryOperations`` option.
 
+- Adds ``AllowShortNamespacesOnASingleLine`` option.
+
 libclang
 --------
 - Add ``clang_isBeforeInTranslationUnit``. Given two source locations, it determines
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 300bd770f993da..d9fa2780034b45 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -383,7 +383,7 @@ class LineJoiner {
              ClosingLineIndex == I[J]->MatchingClosingBlockLineIndex &&
              I[J]->Last->TotalLength < Limit;
              ++J, --ClosingLineIndex) {
-          Limit -= I[J]->Last->TotalLength;
+          Limit -= I[J]->Last->TotalLength + 1;
 
           // Reduce indent level for bodies of namespaces which were compacted,
           // but only if their content was indented in the first place.
@@ -647,9 +647,10 @@ class LineJoiner {
     // Check if it's a namespace inside a namespace, and call recursively if so.
     // '3' is the sizes of the whitespace and closing brace for " _inner_ }".
     if (I[1]->First->is(tok::kw_namespace)) {
-      if (I[1]->Last->is(tok::comment))
+      if (I[1]->Last->is(tok::comment) || !Style.CompactNamespaces)
         return 0;
 
+      assert(Limit >= I[1]->Last->TotalLength + 3);
       const unsigned InnerLimit = Limit - I[1]->Last->TotalLength - 3;
       const unsigned MergedLines = tryMergeNamespace(I + 1, E, InnerLimit);
       if (!MergedLines)
@@ -661,7 +662,7 @@ class LineJoiner {
       // Check that the line after the inner result starts with a closing brace
       // which we are permitted to merge into one line.
       if (I[N]->First->is(tok::r_brace) && !I[N]->First->MustBreakBefore &&
-          !I[MergedLines + 1]->Last->is(tok::comment) &&
+          I[MergedLines + 1]->Last->isNot(tok::comment) &&
           nextNLinesFitInto(I, I + N + 1, Limit)) {
         return N;
       }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 434f0a0dfb6079..14955342de8270 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -4484,7 +4484,7 @@ TEST_F(FormatTest, FormatsCompactNamespaces) {
                "} // namespace A",
                Style);
 
-  Style.ColumnLimit = 40;
+  Style.ColumnLimit = 41;
   verifyFormat("namespace aaaaaaaaaa {\n"
                "namespace bbbbbbbbbb {\n"
                "}} // namespace aaaaaaaaaa::bbbbbbbbbb",
@@ -4504,6 +4504,16 @@ TEST_F(FormatTest, FormatsCompactNamespaces) {
                "} // namespace bbbbbb\n"
                "} // namespace aaaaaa",
                Style);
+
+  verifyFormat("namespace a { namespace b { namespace c {\n"
+               "}}} // namespace a::b::c",
+               Style);
+
+  verifyFormat("namespace a { namespace b {\n"
+               "namespace cc {\n"
+               "}}} // namespace a::b::cc",
+               Style);
+
   Style.ColumnLimit = 80;
 
   // Extra semicolon after 'inner' closing brace prevents merging
@@ -27985,6 +27995,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   auto BaseStyle = getLLVMStyle();
   BaseStyle.AllowShortNamespacesOnASingleLine = true;
   BaseStyle.FixNamespaceComments = false;
+  BaseStyle.CompactNamespaces = true;
 
   auto Style = BaseStyle;
 
@@ -27999,8 +28010,9 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                Style);
 
   // Trailing comments prevent merging.
-  verifyFormat("namespace foo {\n"
-               "namespace baz { class qux; } // comment\n"
+  verifyFormat("namespace foo { namespace baz {\n"
+               "class qux;\n"
+               "} // comment\n"
                "}",
                Style);
 
@@ -28015,12 +28027,23 @@ TEST_F(FormatTest, ShortNamespacesOption) {
 
   // Nested namespaces.
   verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
+
+  // Without CompactNamespaces, we won't merge consecutive namespace
+  // declarations
+  Style.CompactNamespaces = false;
+  verifyFormat("namespace foo {\n"
+               "namespace bar { class baz; }\n"
+               "}",
+               Style);
+
   verifyFormat("namespace foo {\n"
                "namespace bar { class baz; }\n"
                "namespace qux { class quux; }\n"
                "}",
                Style);
 
+  Style = BaseStyle;
+
   // Varying inner content.
   verifyFormat("namespace foo {\n"
                "int f() { return 5; }\n"
@@ -28029,7 +28052,7 @@ TEST_F(FormatTest, ShortNamespacesOption) {
   verifyFormat("namespace foo { template <T> struct bar; }", Style);
   verifyFormat("namespace foo { constexpr int num = 42; }", Style);
 
-  // Validate wrapping scenarios around the ColumnLimit.
+  // Validate nested namespace wrapping scenarios around the ColumnLimit.
   Style.ColumnLimit = 64;
 
   // Validate just under the ColumnLimit.
@@ -28038,22 +28061,24 @@ TEST_F(FormatTest, ShortNamespacesOption) {
       Style);
 
   // Validate just over the ColumnLimit.
-  verifyFormat("namespace foo {\n"
-               "namespace bar { namespace baz { class quux; } }\n"
-               "}",
+  verifyFormat("namespace foo { namespace baar { namespace baaz {\n"
+               "class quux;\n"
+               "}}}",
                Style);
 
-  verifyFormat("namespace foo {\n"
-               "namespace bar {\n"
-               "namespace baz { namespace qux { class quux; } }\n"
-               "}\n"
-               "}",
-               Style);
+  verifyFormat(
+      "namespace foo { namespace bar { namespace baz { namespace qux {\n"
+      "class quux;\n"
+      "}}}}",
+      Style);
 
   // Validate that the ColumnLimit logic accounts for trailing content as well.
-  verifyFormat("namespace foo {\n"
-               "namespace bar { namespace baz { class qux; } }\n"
-               "} // extra",
+  verifyFormat("namespace foo { namespace bar { class qux; } } // extra",
+               Style);
+
+  verifyFormat("namespace foo { namespace bar { namespace baz {\n"
+               "class qux;\n"
+               "}}} // extra",
                Style);
 
   // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
@@ -28068,41 +28093,24 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                  "}",
                  Style);
 
-  Style = BaseStyle;
-  Style.CompactNamespaces = true;
   verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
 
-  // If we can't merge an outer nested namespaces, but can merge an inner
-  // nested namespace, then CompactNamespaces will merge the outer namespace
-  // first, preventing the merging of the inner namespace.
-  verifyFormat("namespace foo { namespace baz {\n"
-               "class qux;\n"
-               "} // comment\n"
-               "}",
-               Style);
-
-  // This option doesn't really work with FixNamespaceComments and nested
-  // namespaces. Code should use the concatenated namespace syntax.  e.g.
-  // 'namespace foo::bar'.
+  // FIXME: Ideally AllowShortNamespacesOnASingleLine would disable the trailing
+  // namespace comment from 'FixNamespaceComments', as it's not really necessary
+  // in this scenario, but the two options work at very different layers of the
+  // formatter, so I'm not sure how to make them interact.
+  //
+  // As it stands, the trailing comment will be added and likely make the line
+  // too long to fit within the ColumnLimit, reducing the how likely the line
+  // will still fit on a single line. The recommendation for now is to use the
+  // concatenated namespace syntax instead. e.g. 'namespace foo::bar'
   Style = BaseStyle;
   Style.FixNamespaceComments = true;
 
   verifyFormat(
-      "namespace foo {\n"
-      "namespace bar { namespace baz { class qux; } } // namespace bar\n"
-      "} // namespace foo",
-      "namespace foo { namespace bar { namespace baz { class qux; } } }",
-      Style);
-
-  // This option doesn't really make any sense with ShortNamespaceLines = 0.
-  Style.ShortNamespaceLines = 0;
-
-  verifyFormat(
-      "namespace foo {\n"
-      "namespace bar {\n"
-      "namespace baz { class qux; } // namespace baz\n"
-      "} // namespace bar\n"
-      "} // namespace foo",
+      "namespace foo { namespace bar { namespace baz {\n"
+      "class qux;\n"
+      "}}} // namespace foo::bar::baz",
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
       Style);
 }

>From dd3cecb8381a9c8bbda0e319b0d46d541d2761a8 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Tue, 22 Oct 2024 10:59:24 -0700
Subject: [PATCH 11/12] Remove ColumnLimit=0 tests

---
 clang/unittests/Format/FormatTest.cpp | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 14955342de8270..1221dabb9316c8 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -28081,20 +28081,6 @@ TEST_F(FormatTest, ShortNamespacesOption) {
                "}}} // extra",
                Style);
 
-  // No ColumnLimit, allows long nested one-liners, but also leaves multi-line
-  // instances alone.
-  Style.ColumnLimit = 0;
-  verifyFormat(
-      "namespace foo { namespace bar { namespace baz { class qux; } } }",
-      Style);
-
-  verifyNoChange("namespace foo {\n"
-                 "namespace bar { namespace baz { class qux; } }\n"
-                 "}",
-                 Style);
-
-  verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
-
   // FIXME: Ideally AllowShortNamespacesOnASingleLine would disable the trailing
   // namespace comment from 'FixNamespaceComments', as it's not really necessary
   // in this scenario, but the two options work at very different layers of the

>From 1733719d95d86edb01676fd6ee95abc1e6a94264 Mon Sep 17 00:00:00 2001
From: Galen Elias <gelias at microsoft.com>
Date: Fri, 8 Nov 2024 15:14:18 -0800
Subject: [PATCH 12/12] Remove blank line in release notes

---
 clang/docs/ReleaseNotes.rst | 1 -
 1 file changed, 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e6381fa41c5ba1..5eeb92ff0dc291 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -841,7 +841,6 @@ clang-format
   ``Never``, and ``true`` to ``Always``.
 - Adds ``RemoveEmptyLinesInUnwrappedLines`` option.
 - Adds ``KeepFormFeed`` option and set it to ``true`` for ``GNU`` style.
-
 - Adds ``AllowShortNamespacesOnASingleLine`` option.
 
 libclang



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