4 files changed, 44 insertions, 4 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 3fed32f6f4c..44e6ad4232e 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -701,8 +701,18 @@ unsigned ContinuationIndenter::addTokenOnNewLine(LineState &State,
     State.Stack.back().BreakBeforeParameter = false;
 
   if (!DryRun) {
+    unsigned MaxEmptyLinesToKeep = Style.MaxEmptyLinesToKeep + 1;
+    if (Current.is(tok::r_brace) && Current.MatchingParen &&
+        // Only strip trailing empty lines for l_braces that have children, i.e.
+        // for function expressions (lambdas, arrows, etc).
+        !Current.MatchingParen->Children.empty()) {
+      // lambdas and arrow functions are expressions, thus their r_brace is not
+      // on its own line, and thus not covered by UnwrappedLineFormatter's logic
+      // about removing empty lines on closing blocks. Special case them here.
+      MaxEmptyLinesToKeep = 1;
+    }
     unsigned Newlines = std::max(
-        1u, std::min(Current.NewlinesBefore, Style.MaxEmptyLinesToKeep + 1));
+        1u, std::min(Current.NewlinesBefore, MaxEmptyLinesToKeep));
     bool ContinuePPDirective =
         State.Line->InPPDirective && State.Line->Type != LT_ImportStatement;
     Whitespaces.replaceWhitespace(Current, Newlines, State.Column, State.Column,
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index a82cd5abe27..2e9d803a191 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -1117,6 +1117,9 @@ void UnwrappedLineFormatter::formatFirstToken(const AnnotatedLine &Line,
       (!RootToken.Next ||
        (RootToken.Next->is(tok::semi) && !RootToken.Next->Next)))
     Newlines = std::min(Newlines, 1u);
+  // Remove empty lines at the start of nested blocks (lambdas/arrow functions)
+  if (PreviousLine == nullptr && Line.Level > 0)
+    Newlines = std::min(Newlines, 1u);
   if (Newlines == 0 && !RootToken.IsFirst)
     Newlines = 1;
   if (RootToken.IsFirst && !RootToken.HasUnescapedNewline)
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 7fbf01dc129..acff8d32320 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -70,18 +70,23 @@ protected:
     return getStyleWithColumns(getGoogleStyle(), ColumnLimit);
   }
 
-  void verifyFormat(llvm::StringRef Code,
+  void verifyFormat(llvm::StringRef Expected, llvm::StringRef Code,
                     const FormatStyle &Style = getLLVMStyle()) {
-    EXPECT_EQ(Code.str(), format(test::messUp(Code), Style));
+    EXPECT_EQ(Expected.str(), format(Code, Style));
     if (Style.Language == FormatStyle::LK_Cpp) {
       // Objective-C++ is a superset of C++, so everything checked for C++
       // needs to be checked for Objective-C++ as well.
       FormatStyle ObjCStyle = Style;
       ObjCStyle.Language = FormatStyle::LK_ObjC;
-      EXPECT_EQ(Code.str(), format(test::messUp(Code), ObjCStyle));
+      EXPECT_EQ(Expected.str(), format(test::messUp(Code), ObjCStyle));
     }
   }
 
+  void verifyFormat(llvm::StringRef Code,
+                    const FormatStyle &Style = getLLVMStyle()) {
+    verifyFormat(Code, test::messUp(Code), Style);
+  }
+
   void verifyIncompleteFormat(llvm::StringRef Code,
                               const FormatStyle &Style = getLLVMStyle()) {
     EXPECT_EQ(Code.str(),
@@ -11089,6 +11094,17 @@ TEST_F(FormatTest, FormatsLambdas) {
       "    });");
 }
 
+TEST_F(FormatTest, EmptyLinesInLambdas) {
+  verifyFormat("auto lambda = []() {\n"
+               "  x(); //\n"
+               "};",
+               "auto lambda = []() {\n"
+               "\n"
+               "  x(); //\n"
+               "\n"
+               "};");
+}
+
 TEST_F(FormatTest, FormatsBlocks) {
   FormatStyle ShortBlocks = getLLVMStyle();
   ShortBlocks.AllowShortBlocksOnASingleLine = true;
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index 3df01663e9d..3e5abdc098a 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -1606,6 +1606,17 @@ TEST_F(FormatTestJS, TypeInterfaceLineWrapping) {
       Style);
 }
 
+TEST_F(FormatTestJS, RemoveEmptyLinesInArrowFunctions) {
+  verifyFormat("x = () => {\n"
+               "  foo();\n"
+               "};\n",
+               "x = () => {\n"
+               "\n"
+               "  foo();\n"
+               "\n"
+               "};\n");
+}
+
 TEST_F(FormatTestJS, Modules) {
   verifyFormat("import SomeThing from 'some/module.js';");
   verifyFormat("import {X, Y} from 'some/module.js';");