clang/lib/Format/FormatToken.cpp

   1 //===--- FormatToken.cpp - Format C++ code --------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// This file implements specific functions of \c FormatTokens and their
  11 /// roles.
  12 ///
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "FormatToken.h"
  16 #include "ContinuationIndenter.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/Support/Debug.h"
  19 #include <climits>
  20
  21 namespace clang {
  22 namespace format {
  23
  24 const char *getTokenTypeName(TokenType Type) {
  25   static const char *const TokNames[] = {
  26 #define TYPE(X) #X,
  27       LIST_TOKEN_TYPES
  28 #undef TYPE
  29       nullptr};
  30
  31   if (Type < NUM_TOKEN_TYPES)
  32     return TokNames[Type];
  33   llvm_unreachable("unknown TokenType");
  34   return nullptr;
  35 }
  36
  37 // FIXME: This is copy&pasted from Sema. Put it in a common place and remove
  38 // duplication.
  39 bool FormatToken::isSimpleTypeSpecifier() const {
  40   switch (Tok.getKind()) {
  41   case tok::kw_short:
  42   case tok::kw_long:
  43   case tok::kw___int64:
  44   case tok::kw___int128:
  45   case tok::kw_signed:
  46   case tok::kw_unsigned:
  47   case tok::kw_void:
  48   case tok::kw_char:
  49   case tok::kw_int:
  50   case tok::kw_half:
  51   case tok::kw_float:
  52   case tok::kw_double:
  53   case tok::kw___bf16:
  54   case tok::kw__Float16:
  55   case tok::kw___float128:
  56   case tok::kw___ibm128:
  57   case tok::kw_wchar_t:
  58   case tok::kw_bool:
  59 #define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) case tok::kw___##Trait:
  60 #include "clang/Basic/TransformTypeTraits.def"
  61   case tok::annot_typename:
  62   case tok::kw_char8_t:
  63   case tok::kw_char16_t:
  64   case tok::kw_char32_t:
  65   case tok::kw_typeof:
  66   case tok::kw_decltype:
  67   case tok::kw__Atomic:
  68     return true;
  69   default:
  70     return false;
  71   }
  72 }
  73
  74 bool FormatToken::isTypeOrIdentifier() const {
  75   return isSimpleTypeSpecifier() || Tok.isOneOf(tok::kw_auto, tok::identifier);
  76 }
  77
  78 bool FormatToken::isBlockIndentedInitRBrace(const FormatStyle &Style) const {
  79   assert(is(tok::r_brace));
  80   if (!Style.Cpp11BracedListStyle ||
  81       Style.AlignAfterOpenBracket != FormatStyle::BAS_BlockIndent) {
  82     return false;
  83   }
  84   const auto *LBrace = MatchingParen;
  85   assert(LBrace && LBrace->is(tok::l_brace));
  86   if (LBrace->is(BK_BracedInit))
  87     return true;
  88   if (LBrace->Previous && LBrace->Previous->is(tok::equal))
  89     return true;
  90   return false;
  91 }
  92
  93 bool FormatToken::opensBlockOrBlockTypeList(const FormatStyle &Style) const {
  94   // C# Does not indent object initialisers as continuations.
  95   if (is(tok::l_brace) && getBlockKind() == BK_BracedInit && Style.isCSharp())
  96     return true;
  97   if (is(TT_TemplateString) && opensScope())
  98     return true;
  99   return is(TT_ArrayInitializerLSquare) || is(TT_ProtoExtensionLSquare) ||
 100          (is(tok::l_brace) &&
 101           (getBlockKind() == BK_Block || is(TT_DictLiteral) ||
 102            (!Style.Cpp11BracedListStyle && NestingLevel == 0))) ||
 103          (is(tok::less) && (Style.Language == FormatStyle::LK_Proto ||
 104                             Style.Language == FormatStyle::LK_TextProto));
 105 }
 106
 107 TokenRole::~TokenRole() {}
 108
 109 void TokenRole::precomputeFormattingInfos(const FormatToken *Token) {}
 110
 111 unsigned CommaSeparatedList::formatAfterToken(LineState &State,
 112                                               ContinuationIndenter *Indenter,
 113                                               bool DryRun) {
 114   if (!State.NextToken || !State.NextToken->Previous)
 115     return 0;
 116
 117   if (Formats.size() == 1)
 118     return 0; // Handled by formatFromToken
 119
 120   // Ensure that we start on the opening brace.
 121   const FormatToken *LBrace =
 122       State.NextToken->Previous->getPreviousNonComment();
 123   if (!LBrace || !LBrace->isOneOf(tok::l_brace, TT_ArrayInitializerLSquare) ||
 124       LBrace->is(BK_Block) || LBrace->is(TT_DictLiteral) ||
 125       LBrace->Next->is(TT_DesignatedInitializerPeriod)) {
 126     return 0;
 127   }
 128
 129   // Calculate the number of code points we have to format this list. As the
 130   // first token is already placed, we have to subtract it.
 131   unsigned RemainingCodePoints =
 132       Style.ColumnLimit - State.Column + State.NextToken->Previous->ColumnWidth;
 133
 134   // Find the best ColumnFormat, i.e. the best number of columns to use.
 135   const ColumnFormat *Format = getColumnFormat(RemainingCodePoints);
 136
 137   // If no ColumnFormat can be used, the braced list would generally be
 138   // bin-packed. Add a severe penalty to this so that column layouts are
 139   // preferred if possible.
 140   if (!Format)
 141     return 10000;
 142
 143   // Format the entire list.
 144   unsigned Penalty = 0;
 145   unsigned Column = 0;
 146   unsigned Item = 0;
 147   while (State.NextToken != LBrace->MatchingParen) {
 148     bool NewLine = false;
 149     unsigned ExtraSpaces = 0;
 150
 151     // If the previous token was one of our commas, we are now on the next item.
 152     if (Item < Commas.size() && State.NextToken->Previous == Commas[Item]) {
 153       if (!State.NextToken->isTrailingComment()) {
 154         ExtraSpaces += Format->ColumnSizes[Column] - ItemLengths[Item];
 155         ++Column;
 156       }
 157       ++Item;
 158     }
 159
 160     if (Column == Format->Columns || State.NextToken->MustBreakBefore) {
 161       Column = 0;
 162       NewLine = true;
 163     }
 164
 165     // Place token using the continuation indenter and store the penalty.
 166     Penalty += Indenter->addTokenToState(State, NewLine, DryRun, ExtraSpaces);
 167   }
 168   return Penalty;
 169 }
 170
 171 unsigned CommaSeparatedList::formatFromToken(LineState &State,
 172                                              ContinuationIndenter *Indenter,
 173                                              bool DryRun) {
 174   // Formatting with 1 Column isn't really a column layout, so we don't need the
 175   // special logic here. We can just avoid bin packing any of the parameters.
 176   if (Formats.size() == 1 || HasNestedBracedList)
 177     State.Stack.back().AvoidBinPacking = true;
 178   return 0;
 179 }
 180
 181 // Returns the lengths in code points between Begin and End (both included),
 182 // assuming that the entire sequence is put on a single line.
 183 static unsigned CodePointsBetween(const FormatToken *Begin,
 184                                   const FormatToken *End) {
 185   assert(End->TotalLength >= Begin->TotalLength);
 186   return End->TotalLength - Begin->TotalLength + Begin->ColumnWidth;
 187 }
 188
 189 void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
 190   // FIXME: At some point we might want to do this for other lists, too.
 191   if (!Token->MatchingParen ||
 192       !Token->isOneOf(tok::l_brace, TT_ArrayInitializerLSquare)) {
 193     return;
 194   }
 195
 196   // In C++11 braced list style, we should not format in columns unless they
 197   // have many items (20 or more) or we allow bin-packing of function call
 198   // arguments.
 199   if (Style.Cpp11BracedListStyle && !Style.BinPackArguments &&
 200       Commas.size() < 19) {
 201     return;
 202   }
 203
 204   // Limit column layout for JavaScript array initializers to 20 or more items
 205   // for now to introduce it carefully. We can become more aggressive if this
 206   // necessary.
 207   if (Token->is(TT_ArrayInitializerLSquare) && Commas.size() < 19)
 208     return;
 209
 210   // Column format doesn't really make sense if we don't align after brackets.
 211   if (Style.AlignAfterOpenBracket == FormatStyle::BAS_DontAlign)
 212     return;
 213
 214   FormatToken *ItemBegin = Token->Next;
 215   while (ItemBegin->isTrailingComment())
 216     ItemBegin = ItemBegin->Next;
 217   SmallVector<bool, 8> MustBreakBeforeItem;
 218
 219   // The lengths of an item if it is put at the end of the line. This includes
 220   // trailing comments which are otherwise ignored for column alignment.
 221   SmallVector<unsigned, 8> EndOfLineItemLength;
 222   MustBreakBeforeItem.reserve(Commas.size() + 1);
 223   EndOfLineItemLength.reserve(Commas.size() + 1);
 224   ItemLengths.reserve(Commas.size() + 1);
 225
 226   bool HasSeparatingComment = false;
 227   for (unsigned i = 0, e = Commas.size() + 1; i != e; ++i) {
 228     assert(ItemBegin);
 229     // Skip comments on their own line.
 230     while (ItemBegin->HasUnescapedNewline && ItemBegin->isTrailingComment()) {
 231       ItemBegin = ItemBegin->Next;
 232       HasSeparatingComment = i > 0;
 233     }
 234
 235     MustBreakBeforeItem.push_back(ItemBegin->MustBreakBefore);
 236     if (ItemBegin->is(tok::l_brace))
 237       HasNestedBracedList = true;
 238     const FormatToken *ItemEnd = nullptr;
 239     if (i == Commas.size()) {
 240       ItemEnd = Token->MatchingParen;
 241       const FormatToken *NonCommentEnd = ItemEnd->getPreviousNonComment();
 242       ItemLengths.push_back(CodePointsBetween(ItemBegin, NonCommentEnd));
 243       if (Style.Cpp11BracedListStyle &&
 244           !ItemEnd->Previous->isTrailingComment()) {
 245         // In Cpp11 braced list style, the } and possibly other subsequent
 246         // tokens will need to stay on a line with the last element.
 247         while (ItemEnd->Next && !ItemEnd->Next->CanBreakBefore)
 248           ItemEnd = ItemEnd->Next;
 249       } else {
 250         // In other braced lists styles, the "}" can be wrapped to the new line.
 251         ItemEnd = Token->MatchingParen->Previous;
 252       }
 253     } else {
 254       ItemEnd = Commas[i];
 255       // The comma is counted as part of the item when calculating the length.
 256       ItemLengths.push_back(CodePointsBetween(ItemBegin, ItemEnd));
 257
 258       // Consume trailing comments so the are included in EndOfLineItemLength.
 259       if (ItemEnd->Next && !ItemEnd->Next->HasUnescapedNewline &&
 260           ItemEnd->Next->isTrailingComment()) {
 261         ItemEnd = ItemEnd->Next;
 262       }
 263     }
 264     EndOfLineItemLength.push_back(CodePointsBetween(ItemBegin, ItemEnd));
 265     // If there is a trailing comma in the list, the next item will start at the
 266     // closing brace. Don't create an extra item for this.
 267     if (ItemEnd->getNextNonComment() == Token->MatchingParen)
 268       break;
 269     ItemBegin = ItemEnd->Next;
 270   }
 271
 272   // Don't use column layout for lists with few elements and in presence of
 273   // separating comments.
 274   if (Commas.size() < 5 || HasSeparatingComment)
 275     return;
 276
 277   if (Token->NestingLevel != 0 && Token->is(tok::l_brace) && Commas.size() < 19)
 278     return;
 279
 280   // We can never place more than ColumnLimit / 3 items in a row (because of the
 281   // spaces and the comma).
 282   unsigned MaxItems = Style.ColumnLimit / 3;
 283   SmallVector<unsigned> MinSizeInColumn;
 284   MinSizeInColumn.reserve(MaxItems);
 285   for (unsigned Columns = 1; Columns <= MaxItems; ++Columns) {
 286     ColumnFormat Format;
 287     Format.Columns = Columns;
 288     Format.ColumnSizes.resize(Columns);
 289     MinSizeInColumn.assign(Columns, UINT_MAX);
 290     Format.LineCount = 1;
 291     bool HasRowWithSufficientColumns = false;
 292     unsigned Column = 0;
 293     for (unsigned i = 0, e = ItemLengths.size(); i != e; ++i) {
 294       assert(i < MustBreakBeforeItem.size());
 295       if (MustBreakBeforeItem[i] || Column == Columns) {
 296         ++Format.LineCount;
 297         Column = 0;
 298       }
 299       if (Column == Columns - 1)
 300         HasRowWithSufficientColumns = true;
 301       unsigned Length =
 302           (Column == Columns - 1) ? EndOfLineItemLength[i] : ItemLengths[i];
 303       Format.ColumnSizes[Column] = std::max(Format.ColumnSizes[Column], Length);
 304       MinSizeInColumn[Column] = std::min(MinSizeInColumn[Column], Length);
 305       ++Column;
 306     }
 307     // If all rows are terminated early (e.g. by trailing comments), we don't
 308     // need to look further.
 309     if (!HasRowWithSufficientColumns)
 310       break;
 311     Format.TotalWidth = Columns - 1; // Width of the N-1 spaces.
 312
 313     for (unsigned i = 0; i < Columns; ++i)
 314       Format.TotalWidth += Format.ColumnSizes[i];
 315
 316     // Don't use this Format, if the difference between the longest and shortest
 317     // element in a column exceeds a threshold to avoid excessive spaces.
 318     if ([&] {
 319           for (unsigned i = 0; i < Columns - 1; ++i)
 320             if (Format.ColumnSizes[i] - MinSizeInColumn[i] > 10)
 321               return true;
 322           return false;
 323         }()) {
 324       continue;
 325     }
 326
 327     // Ignore layouts that are bound to violate the column limit.
 328     if (Format.TotalWidth > Style.ColumnLimit && Columns > 1)
 329       continue;
 330
 331     Formats.push_back(Format);
 332   }
 333 }
 334
 335 const CommaSeparatedList::ColumnFormat *
 336 CommaSeparatedList::getColumnFormat(unsigned RemainingCharacters) const {
 337   const ColumnFormat *BestFormat = nullptr;
 338   for (const ColumnFormat &Format : llvm::reverse(Formats)) {
 339     if (Format.TotalWidth <= RemainingCharacters || Format.Columns == 1) {
 340       if (BestFormat && Format.LineCount > BestFormat->LineCount)
 341         break;
 342       BestFormat = &Format;
 343     }
 344   }
 345   return BestFormat;
 346 }
 347
 348 } // namespace format
 349 } // namespace clang