[clang-format] [PR25010] AllowShortIfStatementsOnASingleLine not working if an "else" statement is present

Summary:
Addressing: PR25010 - https://bugs.llvm.org/show_bug.cgi?id=25010

Code like:

```
    if(true) var++;
    else  {
        var--;
    }
```

is reformatted to be

```
  if (true)
    var++;
  else {
    var--;
  }
```

Even when `AllowShortIfStatementsOnASingleLine` is true

The following revision comes from a +1'd suggestion in the PR to support AllowShortIfElseStatementsOnASingleLine

This suppresses the clause prevents the merging of the if when there is a compound else

Reviewers: klimek, djasper, JonasToth, alexfh, krasimir, reuk
Reviewed By: reuk
Subscribers: reuk, Higuoxing, jdoerfert, cfe-commits
Tags: #clang-tools-extra
Differential Revision: https://reviews.llvm.org/D59087

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@356031 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ClangFormatStyleOptions.rst

@@ -365,10 +365,47 @@ the configuration (without a prefix: ``Auto``).
       };
       void f() { bar(); }
 
+**AllowShortIfStatementsOnASingleLine** (``ShortIfStyle``)
+  Dependent on the value, ``if (a) return 0;`` can be put on a
+  single line.
+
+  Possible values:
+
+  * ``SIS_Never`` (in configuration: ``Never``)
+    Do not allow short if functions.
+
+    .. code-block:: c++
+
+       if (a)
+         return;
+       else
+         return;
+
+  * ``SIS_WithoutElse`` (in configuration: ``WithoutElse``)
+    Allow short if functions on the same line, as long as else
+    is not a compound statement.
 
+    .. code-block:: c++
+
+       if (a) return;
+       else
+         return;
+
+       if (a)
+         return;
+       else {
+         return;
+       }
 
-**AllowShortIfStatementsOnASingleLine** (``bool``)
-  If ``true``, ``if (a) return;`` can be put on a single line.
+  * ``SIS_Always`` (in configuration: ``Always``)
+    Allow short if statements even if the else is a compound statement.
+
+    .. code-block:: c++
+
+       if (a) return;
+       else {
+          return;
+       }
 
 **AllowShortLoopsOnASingleLine** (``bool``)
   If ``true``, ``while (true) continue;`` can be put on a single

include/clang/Format/Format.h

@@ -241,8 +241,38 @@ struct FormatStyle {
   /// single line.
   ShortFunctionStyle AllowShortFunctionsOnASingleLine;
 
+  /// Different styles for handling short if lines
+  enum ShortIfStyle {
+    /// Never put short ifs on the same line.
+    /// \code
+    ///   if (a)
+    ///     return ;
+    ///   else {
+    ///     return;
+    ///   }
+    /// \endcode
+    SIS_Never,
+    /// Without else put short ifs on the same line only if
+    /// the else is not a compound statement.
+    /// \code
+    ///   if (a) return;
+    ///   else
+    ///     return;
+    /// \endcode
+    SIS_WithoutElse,
+    /// Always put short ifs on the same line if
+    /// the else is not a compound statement or not.
+    /// \code
+    ///   if (a) return;
+    ///   else {
+    ///     return;
+    ///   }
+    /// \endcode
+    SIS_Always,
+  };
+
   /// If ``true``, ``if (a) return;`` can be put on a single line.
-  bool AllowShortIfStatementsOnASingleLine;
+  ShortIfStyle AllowShortIfStatementsOnASingleLine;
 
   /// If ``true``, ``while (true) continue;`` can be put on a single
   /// line.

lib/Format/Format.cpp

@@ -106,6 +106,18 @@ template <> struct ScalarEnumerationTraits<FormatStyle::ShortFunctionStyle> {
   }
 };
 
+template <> struct ScalarEnumerationTraits<FormatStyle::ShortIfStyle> {
+  static void enumeration(IO &IO, FormatStyle::ShortIfStyle &Value) {
+    IO.enumCase(Value, "Never", FormatStyle::SIS_Never);
+    IO.enumCase(Value, "Always", FormatStyle::SIS_Always);
+    IO.enumCase(Value, "WithoutElse", FormatStyle::SIS_WithoutElse);
+
+    // For backward compatibility.
+    IO.enumCase(Value, "false", FormatStyle::SIS_Never);
+    IO.enumCase(Value, "true", FormatStyle::SIS_WithoutElse);
+  }
+};
+
 template <> struct ScalarEnumerationTraits<FormatStyle::BinPackStyle> {
   static void enumeration(IO &IO, FormatStyle::BinPackStyle &Value) {
     IO.enumCase(Value, "Auto", FormatStyle::BPS_Auto);
@@ -631,7 +643,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
   LLVMStyle.AllowShortBlocksOnASingleLine = false;
   LLVMStyle.AllowShortCaseLabelsOnASingleLine = false;
-  LLVMStyle.AllowShortIfStatementsOnASingleLine = false;
+  LLVMStyle.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Never;
   LLVMStyle.AllowShortLoopsOnASingleLine = false;
   LLVMStyle.AlwaysBreakAfterReturnType = FormatStyle::RTBS_None;
   LLVMStyle.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_None;
@@ -737,7 +749,8 @@ FormatStyle getGoogleStyle(FormatStyle::LanguageKind Language) {
 
   GoogleStyle.AccessModifierOffset = -1;
   GoogleStyle.AlignEscapedNewlines = FormatStyle::ENAS_Left;
-  GoogleStyle.AllowShortIfStatementsOnASingleLine = true;
+  GoogleStyle.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   GoogleStyle.AllowShortLoopsOnASingleLine = true;
   GoogleStyle.AlwaysBreakBeforeMultilineStrings = true;
   GoogleStyle.AlwaysBreakTemplateDeclarations = FormatStyle::BTDS_Yes;
@@ -804,7 +817,7 @@ FormatStyle getGoogleStyle(FormatStyle::LanguageKind Language) {
     GoogleStyle.AlignOperands = false;
     GoogleStyle.AlignTrailingComments = false;
     GoogleStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Empty;
-    GoogleStyle.AllowShortIfStatementsOnASingleLine = false;
+    GoogleStyle.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Never;
     GoogleStyle.AlwaysBreakBeforeMultilineStrings = false;
     GoogleStyle.BreakBeforeBinaryOperators = FormatStyle::BOS_NonAssignment;
     GoogleStyle.ColumnLimit = 100;
@@ -846,7 +859,8 @@ FormatStyle getGoogleStyle(FormatStyle::LanguageKind Language) {
 FormatStyle getChromiumStyle(FormatStyle::LanguageKind Language) {
   FormatStyle ChromiumStyle = getGoogleStyle(Language);
   if (Language == FormatStyle::LK_Java) {
-    ChromiumStyle.AllowShortIfStatementsOnASingleLine = true;
+    ChromiumStyle.AllowShortIfStatementsOnASingleLine =
+        FormatStyle::SIS_WithoutElse;
     ChromiumStyle.BreakAfterJavaFieldAnnotations = true;
     ChromiumStyle.ContinuationIndentWidth = 8;
     ChromiumStyle.IndentWidth = 4;
@@ -859,12 +873,12 @@ FormatStyle getChromiumStyle(FormatStyle::LanguageKind Language) {
     };
     ChromiumStyle.SortIncludes = true;
   } else if (Language == FormatStyle::LK_JavaScript) {
-    ChromiumStyle.AllowShortIfStatementsOnASingleLine = false;
+    ChromiumStyle.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Never;
     ChromiumStyle.AllowShortLoopsOnASingleLine = false;
   } else {
     ChromiumStyle.AllowAllParametersOfDeclarationOnNextLine = false;
     ChromiumStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Inline;
-    ChromiumStyle.AllowShortIfStatementsOnASingleLine = false;
+    ChromiumStyle.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Never;
     ChromiumStyle.AllowShortLoopsOnASingleLine = false;
     ChromiumStyle.BinPackParameters = false;
     ChromiumStyle.DerivePointerAlignment = false;

lib/Format/UnwrappedLineFormatter.cpp

@@ -413,10 +413,12 @@ private:
     if (I[1]->First->isOneOf(tok::semi, tok::kw_if, tok::kw_for, tok::kw_while,
                              TT_LineComment))
       return 0;
-    // Only inline simple if's (no nested if or else).
-    if (I + 2 != E && Line.startsWith(tok::kw_if) &&
-        I[2]->First->is(tok::kw_else))
-      return 0;
+    // Only inline simple if's (no nested if or else), unless specified
+    if (Style.AllowShortIfStatementsOnASingleLine != FormatStyle::SIS_Always) {
+      if (I + 2 != E && Line.startsWith(tok::kw_if) &&
+          I[2]->First->is(tok::kw_else))
+        return 0;
+    }
     return 1;
   }
 

unittests/Format/FormatTest.cpp

@@ -439,7 +439,8 @@ TEST_F(FormatTest, FormatIfWithoutCompoundStatement) {
 
   FormatStyle AllowsMergedIf = getLLVMStyle();
   AllowsMergedIf.AlignEscapedNewlines = FormatStyle::ENAS_Left;
-  AllowsMergedIf.AllowShortIfStatementsOnASingleLine = true;
+  AllowsMergedIf.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   verifyFormat("if (a)\n"
                "  // comment\n"
                "  f();",
@@ -487,6 +488,41 @@ TEST_F(FormatTest, FormatIfWithoutCompoundStatement) {
   verifyFormat("if (a)\n  return;", AllowsMergedIf);
 }
 
+TEST_F(FormatTest, FormatIfWithoutCompoundStatementButElseWith) {
+  FormatStyle AllowsMergedIf = getLLVMStyle();
+  AllowsMergedIf.AlignEscapedNewlines = FormatStyle::ENAS_Left;
+  AllowsMergedIf.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
+  verifyFormat("if (a)\n"
+               "  f();\n"
+               "else {\n"
+               "  g();\n"
+               "}",
+               AllowsMergedIf);
+  verifyFormat("if (a)\n"
+               "  f();\n"
+               "else\n"
+               "  g();\n",
+               AllowsMergedIf);
+
+  AllowsMergedIf.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Always;
+
+  verifyFormat("if (a) f();\n"
+               "else {\n"
+               "  g();\n"
+               "}",
+               AllowsMergedIf);
+  verifyFormat("if (a) f();\n"
+               "else {\n"
+               "  if (a) f();\n"
+               "  else {\n"
+               "    g();\n"
+               "  }\n"
+               "  g();\n"
+               "}",
+               AllowsMergedIf);
+}
+
 TEST_F(FormatTest, FormatLoopsWithoutCompoundStatement) {
   FormatStyle AllowsMergedLoops = getLLVMStyle();
   AllowsMergedLoops.AllowShortLoopsOnASingleLine = true;
@@ -515,7 +551,8 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
   AllowSimpleBracedStatements.ColumnLimit = 40;
   AllowSimpleBracedStatements.AllowShortBlocksOnASingleLine = true;
 
-  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine = true;
+  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   AllowSimpleBracedStatements.AllowShortLoopsOnASingleLine = true;
 
   AllowSimpleBracedStatements.BreakBeforeBraces = FormatStyle::BS_Custom;
@@ -563,7 +600,8 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
                "};",
                AllowSimpleBracedStatements);
 
-  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine = false;
+  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_Never;
   verifyFormat("if (true) {}", AllowSimpleBracedStatements);
   verifyFormat("if (true) {\n"
                "  f();\n"
@@ -588,7 +626,8 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
                "}",
                AllowSimpleBracedStatements);
 
-  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine = true;
+  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   AllowSimpleBracedStatements.AllowShortLoopsOnASingleLine = true;
   AllowSimpleBracedStatements.BraceWrapping.AfterControlStatement = true;
 
@@ -625,7 +664,8 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
                "}",
                AllowSimpleBracedStatements);
 
-  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine = false;
+  AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_Never;
   verifyFormat("if (true) {}", AllowSimpleBracedStatements);
   verifyFormat("if (true)\n"
                "{\n"
@@ -659,7 +699,7 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
 TEST_F(FormatTest, ShortBlocksInMacrosDontMergeWithCodeAfterMacro) {
   FormatStyle Style = getLLVMStyleWithColumns(60);
   Style.AllowShortBlocksOnASingleLine = true;
-  Style.AllowShortIfStatementsOnASingleLine = true;
+  Style.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_WithoutElse;
   Style.BreakBeforeBraces = FormatStyle::BS_Allman;
   EXPECT_EQ("#define A                                                  \\\n"
             "  if (HANDLEwernufrnuLwrmviferuvnierv)                     \\\n"
@@ -3157,7 +3197,7 @@ TEST_F(FormatTest, GraciouslyHandleIncorrectPreprocessorConditions) {
 
 TEST_F(FormatTest, FormatsJoinedLinesOnSubsequentRuns) {
   FormatStyle SingleLine = getLLVMStyle();
-  SingleLine.AllowShortIfStatementsOnASingleLine = true;
+  SingleLine.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_WithoutElse;
   verifyFormat("#if 0\n"
                "#elif 1\n"
                "#endif\n"
@@ -8000,7 +8040,8 @@ TEST_F(FormatTest, FormatHashIfExpressions) {
 
 TEST_F(FormatTest, MergeHandlingInTheFaceOfPreprocessorDirectives) {
   FormatStyle AllowsMergedIf = getGoogleStyle();
-  AllowsMergedIf.AllowShortIfStatementsOnASingleLine = true;
+  AllowsMergedIf.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   verifyFormat("void f() { f(); }\n#error E", AllowsMergedIf);
   verifyFormat("if (true) return 42;\n#error E", AllowsMergedIf);
   verifyFormat("if (true)\n#error E\n  return 42;", AllowsMergedIf);
@@ -10425,7 +10466,8 @@ TEST_F(FormatTest, AllmanBraceBreaking) {
   AllmanBraceStyle.ColumnLimit = 80;
 
   FormatStyle BreakBeforeBraceShortIfs = AllmanBraceStyle;
-  BreakBeforeBraceShortIfs.AllowShortIfStatementsOnASingleLine = true;
+  BreakBeforeBraceShortIfs.AllowShortIfStatementsOnASingleLine =
+      FormatStyle::SIS_WithoutElse;
   BreakBeforeBraceShortIfs.AllowShortLoopsOnASingleLine = true;
   verifyFormat("void f(bool b)\n"
                "{\n"
@@ -10887,7 +10929,6 @@ TEST_F(FormatTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(AllowAllParametersOfDeclarationOnNextLine);
   CHECK_PARSE_BOOL(AllowShortBlocksOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortCaseLabelsOnASingleLine);
-  CHECK_PARSE_BOOL(AllowShortIfStatementsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortLoopsOnASingleLine);
   CHECK_PARSE_BOOL(BinPackArguments);
   CHECK_PARSE_BOOL(BinPackParameters);
@@ -11150,6 +11191,20 @@ TEST_F(FormatTest, ParsesConfiguration) {
   CHECK_PARSE("NamespaceIndentation: All", NamespaceIndentation,
               FormatStyle::NI_All);
 
+  Style.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_Always;
+  CHECK_PARSE("AllowShortIfStatementsOnASingleLine: Never",
+              AllowShortIfStatementsOnASingleLine, FormatStyle::SIS_Never);
+  CHECK_PARSE("AllowShortIfStatementsOnASingleLine: WithoutElse",
+              AllowShortIfStatementsOnASingleLine,
+              FormatStyle::SIS_WithoutElse);
+  CHECK_PARSE("AllowShortIfStatementsOnASingleLine: Always",
+              AllowShortIfStatementsOnASingleLine, FormatStyle::SIS_Always);
+  CHECK_PARSE("AllowShortIfStatementsOnASingleLine: false",
+              AllowShortIfStatementsOnASingleLine, FormatStyle::SIS_Never);
+  CHECK_PARSE("AllowShortIfStatementsOnASingleLine: true",
+              AllowShortIfStatementsOnASingleLine,
+              FormatStyle::SIS_WithoutElse);
+
   // FIXME: This is required because parsing a configuration simply overwrites
   // the first N elements of the list instead of resetting it.
   Style.ForEachMacros.clear();

unittests/Format/FormatTestSelective.cpp

@@ -98,7 +98,7 @@ TEST_F(FormatTestSelective, ReformatsMovedLines) {
 }
 
 TEST_F(FormatTestSelective, FormatsIfWithoutCompoundStatement) {
-  Style.AllowShortIfStatementsOnASingleLine = true;
+  Style.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_WithoutElse;
   EXPECT_EQ("if (a) return;", format("if(a)\nreturn;", 7, 1));
   EXPECT_EQ("if (a) return; // comment",
             format("if(a)\nreturn; // comment", 20, 1));