clang-format: introduce InlineOnly short function style

[Typz]

Summary

This is the same as Inline, except it does not imply all empty
functions are merged: with this style, empty functions are merged only
if they also match the 'inline' criteria (i.e. defined in a class).

This is helpful to avoid inlining functions in implementations files.

[djasper]

include/clang/Format/Format.h

234

I'd prefer these functions not to be in the public header file. They are implementation details. Either find a header/cpp-file in the lib/ directory to place them in or just remove them for now. They are both still quite small and called only twice each.

unittests/Format/FormatTest.cpp

6530

Missing line break.

6548

Missing line break. Generally use clang-format on the patches :).

[Typz]

include/clang/Format/Format.h

234

This is similar to the isCpp() method, to provide a better abstraction in the implementation.
I cannot find any better place, so I will remove them.

[Typz]

Fix according to review comments

[djasper]

Looks good.

include/clang/Format/Format.h

struct FormatStyle {
   /// \endcode
   bool AllowShortCaseLabelsOnASingleLine;
 
   /// \brief Different styles for merging short functions containing at most one
   /// statement.
   enum ShortFunctionStyle {
     /// \brief Never merge functions into a single line.
     SFS_None,
+    /// \brief Only merge functions defined inside a class. Same as "inline",
+    /// except it does not implies "empty": i.e. top level empty functions
+    /// are not merged either.
+    /// \code
+    ///   class Foo {
+    ///     void f() { foo(); }
+    ///   };
+    ///   void f() {
+    ///     foo();
+    ///   }
+    ///   void f() {
+    ///   }
+    /// \endcode
+    SFS_InlineOnly,
     /// \brief Only merge empty functions.
     /// \code
-    ///   void f() { bar(); }
+    ///   void f() {}
     ///   void f2() {
     ///     bar2();
     ///   }
     /// \endcode
     SFS_Empty,
     /// \brief Only merge functions defined inside a class. Implies "empty".
     /// \code
     ///   class Foo {
     ///     void f() { foo(); }
     ///   };
+    ///   void f() {
+    ///     foo();
+    ///   }
+    ///   void f() {}
     /// \endcode
     SFS_Inline,
     /// \brief Merge all functions fitting on a single line.
     /// \code
     ///   class Foo {
     ///     void f() { foo(); }
     ///   };
     ///   void f() { bar(); }
     /// \endcode
     SFS_All,
   };
 
   /// \brief Dependent on the value, ``int f() { return 0; }`` can be put on a
   /// single line.
   ShortFunctionStyle AllowShortFunctionsOnASingleLine;
 
   /// \brief If ``true``, ``if (a) return;`` can be put on a single line.
   bool AllowShortIfStatementsOnASingleLine;
 
   /// \brief If ``true``, ``while (true) continue;`` can be put on a single
   /// line.
   bool AllowShortLoopsOnASingleLine;
 
   /// \brief Different ways to break after the function definition return type.
   /// This option is **deprecated** and is retained for backwards compatibility.

lib/Format/Format.cpp

 
 template <> struct ScalarEnumerationTraits<FormatStyle::ShortFunctionStyle> {
   static void enumeration(IO &IO, FormatStyle::ShortFunctionStyle &Value) {
     IO.enumCase(Value, "None", FormatStyle::SFS_None);
     IO.enumCase(Value, "false", FormatStyle::SFS_None);
     IO.enumCase(Value, "All", FormatStyle::SFS_All);
     IO.enumCase(Value, "true", FormatStyle::SFS_All);
     IO.enumCase(Value, "Inline", FormatStyle::SFS_Inline);
+    IO.enumCase(Value, "InlineOnly", FormatStyle::SFS_InlineOnly);
     IO.enumCase(Value, "Empty", FormatStyle::SFS_Empty);
   }
 };
 
 template <> struct ScalarEnumerationTraits<FormatStyle::BinaryOperatorStyle> {
   static void enumeration(IO &IO, FormatStyle::BinaryOperatorStyle &Value) {
     IO.enumCase(Value, "All", FormatStyle::BOS_All);
     IO.enumCase(Value, "true", FormatStyle::BOS_All);

lib/Format/TokenAnnotator.cpp

if (Left.is(tok::l_brace) && Line.Level == 0 &&
       // instead of bin-packing.
       return true;
     if (Right.is(tok::r_brace) && Left.is(tok::l_brace) &&
         !Left.Children.empty())
       // Support AllowShortFunctionsOnASingleLine for JavaScript.
       return Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_None ||
              Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_Empty ||
              (Left.NestingLevel == 0 && Line.Level == 0 &&
-              Style.AllowShortFunctionsOnASingleLine ==
-                  FormatStyle::SFS_Inline);
+              Style.AllowShortFunctionsOnASingleLine &
+                  FormatStyle::SFS_InlineOnly);
   } else if (Style.Language == FormatStyle::LK_Java) {
     if (Right.is(tok::plus) && Left.is(tok::string_literal) && Right.Next &&
         Right.Next->is(tok::string_literal))
       return true;
   } else if (Style.Language == FormatStyle::LK_Cpp ||
              Style.Language == FormatStyle::LK_ObjC ||
              Style.Language == FormatStyle::LK_Proto) {
     if (Left.isStringLiteral() && Right.isStringLiteral())

lib/Format/UnwrappedLineFormatter.cpp

if (TheLine->Last->is(TT_FunctionLBrace) &&
       return tryMergeSimpleBlock(I, E, Limit);
 
     // FIXME: TheLine->Level != 0 might or might not be the right check to do.
     // If necessary, change to something smarter.
     bool MergeShortFunctions =
         Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_All ||
         (Style.AllowShortFunctionsOnASingleLine >= FormatStyle::SFS_Empty &&
          I[1]->First->is(tok::r_brace)) ||
-        (Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_Inline &&
+        (Style.AllowShortFunctionsOnASingleLine & FormatStyle::SFS_InlineOnly &&
          TheLine->Level != 0);
 
     if (Style.CompactNamespaces) {
       if (isNamespaceDeclaration(TheLine)) {
         int i = 0;
         unsigned closingLine = TheLine->MatchingOpeningBlockLineIndex - 1;
         for (; I + 1 + i != E && isNamespaceDeclaration(I[i + 1]) &&
                closingLine == I[i + 1]->MatchingOpeningBlockLineIndex &&

unittests/Format/FormatTest.cpp

TEST_F(FormatTest, PullInlineFunctionDefinitionsIntoSingleLine) {
   // SFS_Inline implies SFS_Empty
   verifyFormat("int f() {}", MergeInlineOnly);
   verifyFormat("class C {\n"
                "  int f() {}\n"
                "};",
                MergeInlineOnly);
 }
 
+TEST_F(FormatTest, PullInlineOnlyFunctionDefinitionsIntoSingleLine) {
+  FormatStyle MergeInlineOnly = getLLVMStyle();
+  MergeInlineOnly.AllowShortFunctionsOnASingleLine =
+      FormatStyle::SFS_InlineOnly;
+  verifyFormat("class C {\n"
+               "  int f() { return 42; }\n"
+               "};",
+               MergeInlineOnly);
+  verifyFormat("int f() {\n"
+               "  return 42;\n"
+               "}",
+               MergeInlineOnly);
+
+  // SFS_InlineOnly does not imply SFS_Empty
+  verifyFormat("class C {\n"
+               "  int f() {}\n"
+               "};",
+               MergeInlineOnly);
+  verifyFormat("int f() {\n"
+               "}",
+               MergeInlineOnly);
+
+  // Also verify behavior when BraceWrapping.AfterFunction = true
+  MergeInlineOnly.BreakBeforeBraces = FormatStyle::BS_Custom;
+  MergeInlineOnly.BraceWrapping.AfterFunction = true;
+  verifyFormat("class C {\n"
+               "  int f() { return 42; }\n"
+               "};",
+               MergeInlineOnly);
+  verifyFormat("int f()\n"
+               "{\n"
+               "  return 42;\n"
+               "}",
+               MergeInlineOnly);
+
+  // SFS_InlineOnly does not imply SFS_Empty
+  verifyFormat("int f()\n"
+               "{\n"
+               "}",
+               MergeInlineOnly);
+  verifyFormat("class C {\n"
+               "  int f() {}\n"
+               "};",
+               MergeInlineOnly);
+}
+
 TEST_F(FormatTest, SplitEmptyFunctionBody) {
   FormatStyle Style = getLLVMStyle();
   Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_None;
   Style.BreakBeforeBraces = FormatStyle::BS_Custom;
   Style.BraceWrapping.AfterFunction = true;
   Style.BraceWrapping.SplitEmptyFunctionBody = false;
   Style.ColumnLimit = 40;