[clang-format] Add option to remove leading blank lines (#91221)

The options regarding which blank lines are kept are also aggregated.
The new option is `KeepEmptyLines`.

This patch was initially part of 9267f8f19a2e502e.  I neglected to check
the server builds before I added it.  It broke clangd.  Jie Fu fixed the
problem in 4c91b49bab0728d4.  I was unaware of it.  I thought the main
branch was still broken.  I reverted the first patch in
70cfece24d6cbb57.  It broke his fix.  He reverted it in
c69ea04fb9738db2.  Now the feature is added again including the fix.

2 files changed, 18 insertions, 5 deletions

diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index aded3ed..2466677a 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/clang/unittests/Format/ConfigParseTest.cpp
@@ -178,8 +178,9 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(IndentWrappedFunctionNames);
   CHECK_PARSE_BOOL(InsertBraces);
   CHECK_PARSE_BOOL(InsertNewlineAtEOF);
-  CHECK_PARSE_BOOL(KeepEmptyLinesAtEOF);
-  CHECK_PARSE_BOOL(KeepEmptyLinesAtTheStartOfBlocks);
+  CHECK_PARSE_BOOL_FIELD(KeepEmptyLines.AtEndOfFile, "KeepEmptyLinesAtEOF");
+  CHECK_PARSE_BOOL_FIELD(KeepEmptyLines.AtStartOfBlock,
+                         "KeepEmptyLinesAtTheStartOfBlocks");
   CHECK_PARSE_BOOL(ObjCSpaceAfterProperty);
   CHECK_PARSE_BOOL(ObjCSpaceBeforeProtocolList);
   CHECK_PARSE_BOOL(Cpp11BracedListStyle);
@@ -226,6 +227,9 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_NESTED_BOOL(BraceWrapping, SplitEmptyFunction);
   CHECK_PARSE_NESTED_BOOL(BraceWrapping, SplitEmptyRecord);
   CHECK_PARSE_NESTED_BOOL(BraceWrapping, SplitEmptyNamespace);
+  CHECK_PARSE_NESTED_BOOL(KeepEmptyLines, AtEndOfFile);
+  CHECK_PARSE_NESTED_BOOL(KeepEmptyLines, AtStartOfBlock);
+  CHECK_PARSE_NESTED_BOOL(KeepEmptyLines, AtStartOfFile);
   CHECK_PARSE_NESTED_BOOL(SpaceBeforeParensOptions, AfterControlStatements);
   CHECK_PARSE_NESTED_BOOL(SpaceBeforeParensOptions, AfterForeachMacros);
   CHECK_PARSE_NESTED_BOOL(SpaceBeforeParensOptions,
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index db1decb..5276e79 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -45,6 +45,10 @@ TEST_F(FormatTest, FormatsGlobalStatementsAt0) {
   verifyFormat("\nint i;", " \n\t \v \f  int i;");
   verifyFormat("int i;\nint j;", "    int i; int j;");
   verifyFormat("int i;\nint j;", "    int i;\n  int j;");
+
+  auto Style = getLLVMStyle();
+  Style.KeepEmptyLines.AtStartOfFile = false;
+  verifyFormat("int i;", " \n\t \v \f  int i;", Style);
 }
 
 TEST_F(FormatTest, FormatsUnwrappedLinesAtFirstFormat) {
@@ -163,7 +167,7 @@ TEST_F(FormatTest, RemovesEmptyLines) {
   auto CustomStyle = getLLVMStyle();
   CustomStyle.BreakBeforeBraces = FormatStyle::BS_Custom;
   CustomStyle.BraceWrapping.AfterNamespace = true;
-  CustomStyle.KeepEmptyLinesAtTheStartOfBlocks = false;
+  CustomStyle.KeepEmptyLines.AtStartOfBlock = false;
   verifyFormat("namespace N\n"
                "{\n"
                "\n"
@@ -389,7 +393,7 @@ TEST_F(FormatTest, RemovesEmptyLines) {
   Style.BreakBeforeBraces = FormatStyle::BS_Custom;
   Style.BraceWrapping.AfterClass = true;
   Style.BraceWrapping.AfterFunction = true;
-  Style.KeepEmptyLinesAtTheStartOfBlocks = false;
+  Style.KeepEmptyLines.AtStartOfBlock = false;
 
   verifyFormat("class Foo\n"
                "{\n"
@@ -21956,6 +21960,11 @@ TEST_F(FormatTest, HandlesUTF8BOM) {
   verifyFormat("\xef\xbb\xbf");
   verifyFormat("\xef\xbb\xbf#include <iostream>");
   verifyFormat("\xef\xbb\xbf\n#include <iostream>");
+
+  auto Style = getLLVMStyle();
+  Style.KeepEmptyLines.AtStartOfFile = false;
+  verifyFormat("\xef\xbb\xbf#include <iostream>",
+               "\xef\xbb\xbf\n#include <iostream>", Style);
 }
 
 // FIXME: Encode Cyrillic and CJK characters below to appease MS compilers.
@@ -27230,7 +27239,7 @@ TEST_F(FormatTest, InsertNewlineAtEOF) {
 
 TEST_F(FormatTest, KeepEmptyLinesAtEOF) {
   FormatStyle Style = getLLVMStyle();
-  Style.KeepEmptyLinesAtEOF = true;
+  Style.KeepEmptyLines.AtEndOfFile = true;
 
   const StringRef Code{"int i;\n\n"};
   verifyNoChange(Code, Style);