[in review/clang-8][clang-format] Introduce the flag which allows not to shrink lines

--------------------------------------------------------------------------
* https://reviews.llvm.org/D53072
--------------------------------------------------------------------------

Currently there's no way to prevent to lines optimization even
if you have intentionally put <CR> to split the line.

In general case it's fine. So I would prefer to have such option
which you can enable in special cases (for me it's an IDE related use case).

Revert this change if upstream clang-format offers better solution.

Change-Id: I01993cc94820b87c61f3968a1a756f74041e2b4f
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

4 files changed, 29 insertions, 3 deletions

diff --git a/include/clang/Format/Format.h b/include/clang/Format/Format.h
index 85dda948c1..8ca6b3e31c 100644
--- a/include/clang/Format/Format.h
+++ b/include/clang/Format/Format.h
@@ -22,6 +22,8 @@
 #include "llvm/Support/Regex.h"
 #include <system_error>
 
+#define KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
+
 namespace clang {
 
 class Lexer;
@@ -1160,6 +1162,16 @@ struct FormatStyle {
   /// \endcode
   bool JavaScriptWrapImports;
 
+  /// If true, no line breaks are optimized out (works only with ColumnLimit = 0)
+  /// \code
+  ///    true:                                  false:
+  ///    int foo(int a,                 vs.     int foo(int a, int b) {
+  ///            int b) {
+  ///      bar();                                 bar();
+  ///    }                                      }
+  /// \endcode
+  bool KeepLineBreaksForNonEmptyLines;
+
   /// If true, the empty line at the start of blocks is kept.
   /// \code
   ///    true:                                  false:
@@ -1726,6 +1738,7 @@ struct FormatStyle {
            IndentWrappedFunctionNames == R.IndentWrappedFunctionNames &&
            JavaScriptQuotes == R.JavaScriptQuotes &&
            JavaScriptWrapImports == R.JavaScriptWrapImports &&
+           KeepLineBreaksForNonEmptyLines == R.KeepLineBreaksForNonEmptyLines &&
            KeepEmptyLinesAtTheStartOfBlocks ==
                R.KeepEmptyLinesAtTheStartOfBlocks &&
            MacroBlockBegin == R.MacroBlockBegin &&
diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 9a2da69e89..df93b21779 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -416,6 +416,8 @@ template <> struct MappingTraits<FormatStyle> {
                    Style.IndentWrappedFunctionNames);
     IO.mapOptional("JavaScriptQuotes", Style.JavaScriptQuotes);
     IO.mapOptional("JavaScriptWrapImports", Style.JavaScriptWrapImports);
+    IO.mapOptional("KeepLineBreaksForNonEmptyLines",
+                   Style.KeepLineBreaksForNonEmptyLines);
     IO.mapOptional("KeepEmptyLinesAtTheStartOfBlocks",
                    Style.KeepEmptyLinesAtTheStartOfBlocks);
     IO.mapOptional("MacroBlockBegin", Style.MacroBlockBegin);
@@ -676,6 +678,7 @@ FormatStyle getLLVMStyle() {
   LLVMStyle.JavaScriptWrapImports = true;
   LLVMStyle.TabWidth = 8;
   LLVMStyle.MaxEmptyLinesToKeep = 1;
+  LLVMStyle.KeepLineBreaksForNonEmptyLines = false;
   LLVMStyle.KeepEmptyLinesAtTheStartOfBlocks = true;
   LLVMStyle.NamespaceIndentation = FormatStyle::NI_None;
   LLVMStyle.ObjCBinPackProtocolList = FormatStyle::BPS_Auto;
@@ -741,6 +744,7 @@ FormatStyle getGoogleStyle(FormatStyle::LanguageKind Language) {
       {"^<ext/.*\\.h>", 2}, {"^<.*\\.h>", 1}, {"^<.*", 2}, {".*", 3}};
   GoogleStyle.IncludeStyle.IncludeIsMainRegex = "([-_](test|unittest))?$";
   GoogleStyle.IndentCaseLabels = true;
+  GoogleStyle.KeepLineBreaksForNonEmptyLines = false;
   GoogleStyle.KeepEmptyLinesAtTheStartOfBlocks = false;
   GoogleStyle.ObjCBinPackProtocolList = FormatStyle::BPS_Never;
   GoogleStyle.ObjCSpaceAfterProperty = false;
diff --git a/lib/Format/UnwrappedLineFormatter.cpp b/lib/Format/UnwrappedLineFormatter.cpp
index 906dae40cb..7e1d805a5f 100644
--- a/lib/Format/UnwrappedLineFormatter.cpp
+++ b/lib/Format/UnwrappedLineFormatter.cpp
@@ -672,7 +672,7 @@ public:
   LineFormatter(ContinuationIndenter *Indenter, WhitespaceManager *Whitespaces,
                 const FormatStyle &Style,
                 UnwrappedLineFormatter *BlockFormatter)
-      : Indenter(Indenter), Whitespaces(Whitespaces), Style(Style),
+      : Indenter(Indenter), Style(Style), Whitespaces(Whitespaces),
         BlockFormatter(BlockFormatter) {}
   virtual ~LineFormatter() {}
 
@@ -760,10 +760,10 @@ protected:
   }
 
   ContinuationIndenter *Indenter;
+  const FormatStyle &Style;
 
 private:
   WhitespaceManager *Whitespaces;
-  const FormatStyle &Style;
   UnwrappedLineFormatter *BlockFormatter;
 };
 
@@ -786,7 +786,8 @@ public:
     while (State.NextToken) {
       bool Newline =
           Indenter->mustBreak(State) ||
-          (Indenter->canBreak(State) && State.NextToken->NewlinesBefore > 0);
+          (State.NextToken->NewlinesBefore > 0 &&
+           (Style.KeepLineBreaksForNonEmptyLines || Indenter->canBreak(State)));
       unsigned Penalty = 0;
       formatChildren(State, Newline, /*DryRun=*/false, Penalty);
       Indenter->addTokenToState(State, Newline, /*DryRun=*/false);
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index f234e287cf..3c94e4c9af 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -349,6 +349,14 @@ TEST_F(FormatTest, RemovesEmptyLines) {
                    "  void funk() {}\n"
                    "};",
                    Style));
+
+  Style.KeepLineBreaksForNonEmptyLines = true;
+  Style.ColumnLimit = 0;
+  EXPECT_EQ("int foo(int a,\n"
+            "        int b) {}",
+            format("int foo(int a,\n"
+                   "        int b) {}",
+                   Style));
 }
 
 TEST_F(FormatTest, RecognizesBinaryOperatorKeywords) {