[clang] [clang-format] Handle merging functions containing only a block comment (PR #74651)

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/74651

Fixed #41854.

>From 40859e0887fd53bbb02be213fcacf3d6d1a5a487 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Wed, 6 Dec 2023 12:01:19 -0800
Subject: [PATCH] [clang-format] Handle merging functions containing only a
 block comment

Fixed #41854.
---
 clang/lib/Format/UnwrappedLineFormatter.cpp   | 15 ++++++++++++---
 clang/unittests/Format/FormatTest.cpp         | 13 +++++++++++++
 clang/unittests/Format/FormatTestComments.cpp | 15 ++++++++-------
 3 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index b4930c2e4621d..56077499c39d5 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -411,9 +411,16 @@ class LineJoiner {
       }
     }
 
+    const auto *LastNonComment = TheLine->getLastNonComment();
+    assert(LastNonComment);
+    // FIXME: There are probably cases where we should use LastNonComment
+    // instead of TheLine->Last.
+
     // Try to merge a function block with left brace unwrapped.
-    if (TheLine->Last->is(TT_FunctionLBrace) && TheLine->First != TheLine->Last)
+    if (LastNonComment->is(TT_FunctionLBrace) &&
+        TheLine->First != LastNonComment) {
       return MergeShortFunctions ? tryMergeSimpleBlock(I, E, Limit) : 0;
+    }
     // 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,
@@ -789,7 +796,8 @@ class LineJoiner {
       }
     }
 
-    if (Line.Last->is(tok::l_brace)) {
+    if (const auto *LastNonComment = Line.getLastNonComment();
+        LastNonComment && LastNonComment->is(tok::l_brace)) {
       if (IsSplitBlock && Line.First == Line.Last &&
           I > AnnotatedLines.begin() &&
           (I[-1]->endsWith(tok::kw_else) || IsCtrlStmt(*I[-1]))) {
@@ -805,7 +813,8 @@ class LineJoiner {
 
       if (ShouldMerge()) {
         // We merge empty blocks even if the line exceeds the column limit.
-        Tok->SpacesRequiredBefore = Style.SpaceInEmptyBlock ? 1 : 0;
+        Tok->SpacesRequiredBefore =
+            (Style.SpaceInEmptyBlock || Line.Last->is(tok::comment)) ? 1 : 0;
         Tok->CanBreakBefore = true;
         return 1;
       } else if (Limit != 0 && !Line.startsWithNamespace() &&
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 8782cb7c49cad..24b2fd599dc39 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -13950,6 +13950,19 @@ TEST_F(FormatTest, PullTrivialFunctionDefinitionsIntoSingleLine) {
                "  void f() { int i; } \\\n"
                "  int j;",
                getLLVMStyleWithColumns(23));
+
+  verifyFormat(
+      "void aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(\n"
+      "    aaaaaaaaaaaaaaaaaa,\n"
+      "    aaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb) {}");
+
+  constexpr StringRef Code{"void foo() { /* Empty */ }"};
+  verifyFormat(Code);
+  verifyFormat(Code, "void foo() { /* Empty */\n"
+                     "}");
+  verifyFormat(Code, "void foo() {\n"
+                     "/* Empty */\n"
+                     "}");
 }
 
 TEST_F(FormatTest, PullEmptyFunctionDefinitionsIntoSingleLine) {
diff --git a/clang/unittests/Format/FormatTestComments.cpp b/clang/unittests/Format/FormatTestComments.cpp
index 9770d5090703c..c249f4d9333fd 100644
--- a/clang/unittests/Format/FormatTestComments.cpp
+++ b/clang/unittests/Format/FormatTestComments.cpp
@@ -386,15 +386,16 @@ TEST_F(FormatTestComments, UnderstandsBlockComments) {
       "  /* Leading comment for bb... */ bbbbbbbbbbbbbbbbbbbbbbbbb);",
       format("f(aaaaaaaaaaaaaaaaaaaaaaaaa    ,   \n"
              "/* Leading comment for bb... */   bbbbbbbbbbbbbbbbbbbbbbbbb);"));
-  EXPECT_EQ(
+
+  verifyFormat(
       "void aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(\n"
       "    aaaaaaaaaaaaaaaaaa,\n"
-      "    aaaaaaaaaaaaaaaaaa) { /*aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa*/\n"
-      "}",
-      format("void      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(\n"
-             "                      aaaaaaaaaaaaaaaaaa  ,\n"
-             "    aaaaaaaaaaaaaaaaaa) {   /*aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa*/\n"
-             "}"));
+      "    aaaaaaaaaaaaaaaaaa) { /*aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa*/ }",
+      "void      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(\n"
+      "                      aaaaaaaaaaaaaaaaaa  ,\n"
+      "    aaaaaaaaaaaaaaaaaa) {   /*aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa*/\n"
+      "}");
+
   verifyFormat("f(/* aaaaaaaaaaaaaaaaaa = */\n"
                "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);");