[clang-format] Add an option to insert a newline at EOF if missing

Closes #38042.

Differential Revision: https://reviews.llvm.org/D141035

Author: owenca

clang/docs/ClangFormatStyleOptions.rst

@@ -3162,6 +3162,9 @@ the configuration (without a prefix: ``Auto``).
       --i;                                      --i;
     while (i);                                } while (i);
 
+**InsertNewlineAtEOF** (``Boolean``) :versionbadge:`clang-format 16`
+  Insert a newline at end of file if missing.
+
 **InsertTrailingCommas** (``TrailingCommaStyle``) :versionbadge:`clang-format 11`
   If set to ``TCS_Wrapped`` will insert trailing commas in container
   literals (arrays and objects) that wrap across multiple lines.

clang/docs/ReleaseNotes.rst

@@ -876,6 +876,7 @@ clang-format
   in C++, C#, Java, and JavaScript.
 - Add ``BreakAfterAttributes`` option for breaking after a group of C++11
   attributes before a function declaration/definition name.
+- Add ``InsertNewlineAtEOF`` option for inserting a newline at EOF if missing.
 
 clang-extdef-mapping
 --------------------

clang/include/clang/Format/Format.h

@@ -2450,6 +2450,10 @@ struct FormatStyle {
   /// \version 15
   bool InsertBraces;
 
+  /// Insert a newline at end of file if missing.
+  /// \version 16
+  bool InsertNewlineAtEOF;
+
   /// The style of inserting trailing commas into container literals.
   enum TrailingCommaStyle : int8_t {
     /// Do not insert trailing commas.
@@ -4151,6 +4155,7 @@ struct FormatStyle {
            IndentWidth == R.IndentWidth &&
            IndentWrappedFunctionNames == R.IndentWrappedFunctionNames &&
            InsertBraces == R.InsertBraces &&
+           InsertNewlineAtEOF == R.InsertNewlineAtEOF &&
            IntegerLiteralSeparator.Binary == R.IntegerLiteralSeparator.Binary &&
            IntegerLiteralSeparator.Decimal ==
                R.IntegerLiteralSeparator.Decimal &&

clang/lib/Format/Format.cpp

@@ -899,6 +899,7 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("IndentWrappedFunctionNames",
                    Style.IndentWrappedFunctionNames);
     IO.mapOptional("InsertBraces", Style.InsertBraces);
+    IO.mapOptional("InsertNewlineAtEOF", Style.InsertNewlineAtEOF);
     IO.mapOptional("InsertTrailingCommas", Style.InsertTrailingCommas);
     IO.mapOptional("IntegerLiteralSeparator", Style.IntegerLiteralSeparator);
     IO.mapOptional("JavaImportGroups", Style.JavaImportGroups);
@@ -1355,6 +1356,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.IndentWidth = 2;
   LLVMStyle.IndentWrappedFunctionNames = false;
   LLVMStyle.InsertBraces = false;
+  LLVMStyle.InsertNewlineAtEOF = false;
   LLVMStyle.InsertTrailingCommas = FormatStyle::TCS_None;
   LLVMStyle.IntegerLiteralSeparator = {/*Binary=*/0, /*Decimal=*/0, /*Hex=*/0};
   LLVMStyle.JavaScriptQuotes = FormatStyle::JSQS_Leave;

clang/lib/Format/TokenAnnotator.cpp

@@ -1289,6 +1289,10 @@ class AnnotatingParser {
         Tok->setType(TT_TrailingReturnArrow);
       }
       break;
+    case tok::eof:
+      if (Style.InsertNewlineAtEOF && Tok->NewlinesBefore == 0)
+        Tok->NewlinesBefore = 1;
+      break;
     default:
       break;
     }

clang/unittests/Format/ConfigParseTest.cpp

@@ -167,6 +167,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(IndentRequiresClause);
   CHECK_PARSE_BOOL(IndentWrappedFunctionNames);
   CHECK_PARSE_BOOL(InsertBraces);
+  CHECK_PARSE_BOOL(InsertNewlineAtEOF);
   CHECK_PARSE_BOOL(KeepEmptyLinesAtTheStartOfBlocks);
   CHECK_PARSE_BOOL(ObjCSpaceAfterProperty);
   CHECK_PARSE_BOOL(ObjCSpaceBeforeProtocolList);

clang/unittests/Format/FormatTest.cpp

@@ -25171,6 +25171,14 @@ TEST_F(FormatTest, BreakAfterAttributes) {
   EXPECT_EQ(Code, format(Code, Style));
 }
 
+TEST_F(FormatTest, InsertNewlineAtEOF) {
+  FormatStyle Style = getLLVMStyle();
+  Style.InsertNewlineAtEOF = true;
+
+  verifyFormat("int i;\n", Style);
+  verifyFormat("int i;\n", "int i;", Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang