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
350