[PATCH] Add ContinuationIndentWidth option

[Kim Gräsman]

Hi djasper, silvas,

Make the indent width used for continuations (lines broken in the middle of an expression) configurable.

http://llvm-reviews.chandlerc.com/D1903

Files:
  include/clang/Format/Format.h
  lib/Format/ContinuationIndenter.cpp
  lib/Format/Format.cpp
  unittests/Format/FormatTest.cpp

Index: include/clang/Format/Format.h
===================================================================
--- include/clang/Format/Format.h
+++ include/clang/Format/Format.h
@@ -235,6 +235,9 @@
   /// \brief If \c false, spaces will be removed before assignment operators.
   bool SpaceBeforeAssignmentOperators;
 
+  /// \brief Indent width for lines broken in the middle of an expression.
+  unsigned ContinuationIndentWidth;
+
   bool operator==(const FormatStyle &R) const {
     return AccessModifierOffset == R.AccessModifierOffset &&
            ConstructorInitializerIndentWidth ==
@@ -282,7 +285,8 @@
            SpacesInCStyleCastParentheses == R.SpacesInCStyleCastParentheses &&
            SpaceAfterControlStatementKeyword ==
                R.SpaceAfterControlStatementKeyword &&
-           SpaceBeforeAssignmentOperators == R.SpaceBeforeAssignmentOperators;
+           SpaceBeforeAssignmentOperators == R.SpaceBeforeAssignmentOperators &&
+           ContinuationIndentWidth == R.ContinuationIndentWidth;
   }
 };
 
Index: lib/Format/ContinuationIndenter.cpp
===================================================================
--- lib/Format/ContinuationIndenter.cpp
+++ lib/Format/ContinuationIndenter.cpp
@@ -265,7 +265,7 @@
   State.Column += Spaces;
   if (Current.is(tok::l_paren) && Previous.isOneOf(tok::kw_if, tok::kw_for))
     // Treat the condition inside an if as if it was a second function
-    // parameter, i.e. let nested calls have an indent of 4.
+    // parameter, i.e. let nested calls have a continuation indent.
     State.Stack.back().LastSpace = State.Column + 1; // 1 is length of "(".
   else if (Previous.is(tok::comma))
     State.Stack.back().LastSpace = State.Column;
@@ -303,9 +303,10 @@
                                                  bool DryRun) {
   const FormatToken &Current = *State.NextToken;
   const FormatToken &Previous = *State.NextToken->Previous;
-  // If we are continuing an expression, we want to indent an extra 4 spaces.
+  // If we are continuing an expression, we want to use the continuation indent.
   unsigned ContinuationIndent =
-      std::max(State.Stack.back().LastSpace, State.Stack.back().Indent) + 4;
+      std::max(State.Stack.back().LastSpace, State.Stack.back().Indent) +
+      Style.ContinuationIndentWidth;
   // Extra penalty that needs to be added because of the way certain line
   // breaks are chosen.
   unsigned Penalty = 0;
@@ -384,10 +385,10 @@
     State.Column = State.Stack.back().Indent;
   } else {
     State.Column = State.Stack.back().Indent;
-    // Ensure that we fall back to indenting 4 spaces instead of just
+    // Ensure that we fall back to the continuation indent width instead of just
     // flushing continuations left.
     if (State.Column == State.FirstIndent)
-      State.Column += 4;
+      State.Column += Style.ContinuationIndentWidth;
   }
 
   if (Current.is(tok::question))
@@ -478,9 +479,10 @@
   }
 
   // In ObjC method declaration we align on the ":" of parameters, but we need
-  // to ensure that we indent parameters on subsequent lines by at least 4.
+  // to ensure that we indent parameters on subsequent lines by at least our
+  // continuation indent width.
   if (Current.Type == TT_ObjCMethodSpecifier)
-    State.Stack.back().Indent += 4;
+    State.Stack.back().Indent += Style.ContinuationIndentWidth;
 
   // Insert scopes created by fake parenthesis.
   const FormatToken *Previous = Current.getPreviousNonComment();
@@ -521,7 +523,7 @@
     if (*I == prec::Conditional ||
         (!SkipFirstExtraIndent && *I > prec::Assignment &&
          !Style.BreakBeforeBinaryOperators))
-      NewParenState.Indent += 4;
+      NewParenState.Indent += Style.ContinuationIndentWidth;
     if (Previous && !Previous->opensScope())
       NewParenState.BreakBeforeParameter = false;
     State.Stack.push_back(NewParenState);
@@ -555,15 +557,17 @@
         NewIndent = State.Stack.back().LastSpace + Style.IndentWidth;
       } else {
         NewIndent = State.Stack.back().LastSpace +
-                    (Style.Cpp11BracedListStyle ? 4 : Style.IndentWidth);
+                    (Style.Cpp11BracedListStyle ? Style.ContinuationIndentWidth
+                                                : Style.IndentWidth);
       }
       const FormatToken *NextNoComment = Current.getNextNonComment();
       AvoidBinPacking = Current.BlockKind == BK_Block ||
                         (NextNoComment &&
                          NextNoComment->Type == TT_DesignatedInitializerPeriod);
     } else {
-      NewIndent = 4 + std::max(State.Stack.back().LastSpace,
-                               State.Stack.back().StartOfFunctionCall);
+      NewIndent = Style.ContinuationIndentWidth +
+                  std::max(State.Stack.back().LastSpace,
+                           State.Stack.back().StartOfFunctionCall);
       AvoidBinPacking = !Style.BinPackParameters ||
                         (Style.ExperimentalAutoDetectBinPacking &&
                          (Current.PackingKind == PPK_OnePerLine ||
Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -163,6 +163,8 @@
                    Style.SpaceAfterControlStatementKeyword);
     IO.mapOptional("SpaceBeforeAssignmentOperators",
                    Style.SpaceBeforeAssignmentOperators);
+    IO.mapOptional("ContinuationIndentWidth",
+                   Style.ContinuationIndentWidth);
   }
 };
 }
@@ -214,6 +216,7 @@
   LLVMStyle.SpacesInCStyleCastParentheses = false;
   LLVMStyle.SpaceAfterControlStatementKeyword = true;
   LLVMStyle.SpaceBeforeAssignmentOperators = true;
+  LLVMStyle.ContinuationIndentWidth = 4;
 
   setDefaultPenalties(LLVMStyle);
   LLVMStyle.PenaltyReturnTypeOnItsOwnLine = 60;
@@ -257,6 +260,7 @@
   GoogleStyle.SpacesInCStyleCastParentheses = false;
   GoogleStyle.SpaceAfterControlStatementKeyword = true;
   GoogleStyle.SpaceBeforeAssignmentOperators = true;
+  GoogleStyle.ContinuationIndentWidth = 4;
 
   setDefaultPenalties(GoogleStyle);
   GoogleStyle.PenaltyReturnTypeOnItsOwnLine = 200;
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -6778,5 +6778,23 @@
                    getGoogleStyle()));
 }
 
+TEST_F(FormatTest, ConfigurableContinuationIndentWidth) {
+  FormatStyle TwoIndent = getLLVMStyleWithColumns(15);
+  TwoIndent.ContinuationIndentWidth = 2;
+
+  EXPECT_EQ("int i =\n"
+            "  longFunction(\n"
+            "    arg);",
+            format("int i = longFunction(arg);", TwoIndent));
+
+  FormatStyle SixIndent = getLLVMStyleWithColumns(20);
+  SixIndent.ContinuationIndentWidth = 6;
+
+  EXPECT_EQ("int i =\n"
+            "      longFunction(\n"
+            "            arg);",
+            format("int i = longFunction(arg);", SixIndent));
+}
+
 } // end namespace tooling
 } // end namespace clang
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