clang-tools  14.0.0git
Format.cpp
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1 //===--- Format.cpp -----------------------------------------*- C++-*------===//
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 #include "Format.h"
9 #include "support/Logger.h"
10 #include "clang/Basic/FileManager.h"
11 #include "clang/Basic/SourceManager.h"
12 #include "clang/Format/Format.h"
13 #include "clang/Lex/Lexer.h"
14 #include "clang/Tooling/Core/Replacement.h"
15 #include "llvm/Support/Unicode.h"
16 
17 namespace clang {
18 namespace clangd {
19 namespace {
20 
21 /// Append closing brackets )]} to \p Code to make it well-formed.
22 /// Clang-format conservatively refuses to format files with unmatched brackets
23 /// as it isn't sure where the errors are and so can't correct.
24 /// When editing, it's reasonable to assume code before the cursor is complete.
25 void closeBrackets(std::string &Code, const format::FormatStyle &Style) {
26  SourceManagerForFile FileSM("mock_file.cpp", Code);
27  auto &SM = FileSM.get();
28  FileID FID = SM.getMainFileID();
29  Lexer Lex(FID, SM.getBufferOrFake(FID), SM,
30  format::getFormattingLangOpts(Style));
31  Token Tok;
32  std::vector<char> Brackets;
33  while (!Lex.LexFromRawLexer(Tok)) {
34  switch(Tok.getKind()) {
35  case tok::l_paren:
36  Brackets.push_back(')');
37  break;
38  case tok::l_brace:
39  Brackets.push_back('}');
40  break;
41  case tok::l_square:
42  Brackets.push_back(']');
43  break;
44  case tok::r_paren:
45  if (!Brackets.empty() && Brackets.back() == ')')
46  Brackets.pop_back();
47  break;
48  case tok::r_brace:
49  if (!Brackets.empty() && Brackets.back() == '}')
50  Brackets.pop_back();
51  break;
52  case tok::r_square:
53  if (!Brackets.empty() && Brackets.back() == ']')
54  Brackets.pop_back();
55  break;
56  default:
57  continue;
58  }
59  }
60  // Attempt to end any open comments first.
61  Code.append("\n// */\n");
62  Code.append(Brackets.rbegin(), Brackets.rend());
63 }
64 
65 static StringRef commentMarker(llvm::StringRef Line) {
66  for (StringRef Marker : {"///", "//"}){
67  auto I = Line.rfind(Marker);
68  if (I != StringRef::npos)
69  return Line.substr(I, Marker.size());
70  }
71  return "";
72 }
73 
74 llvm::StringRef firstLine(llvm::StringRef Code) {
75  return Code.take_until([](char C) { return C == '\n'; });
76 }
77 
78 llvm::StringRef lastLine(llvm::StringRef Code) {
79  llvm::StringRef Rest = Code;
80  while (!Rest.empty() && Rest.back() != '\n')
81  Rest = Rest.drop_back();
82  return Code.substr(Rest.size());
83 }
84 
85 // Filename is needed for tooling::Replacement and some overloads of reformat().
86 // Its value should not affect the outcome. We use the default from reformat().
87 llvm::StringRef Filename = "<stdin>";
88 
89 // tooling::Replacement from overlapping StringRefs: From must be part of Code.
90 tooling::Replacement replacement(llvm::StringRef Code, llvm::StringRef From,
91  llvm::StringRef To) {
92  assert(From.begin() >= Code.begin() && From.end() <= Code.end());
93  // The filename is required but ignored.
94  return tooling::Replacement(Filename, From.data() - Code.data(),
95  From.size(), To);
96 }
97 
98 // High-level representation of incremental formatting changes.
99 // The changes are made in two steps.
100 // 1) a (possibly-empty) set of changes synthesized by clangd (e.g. adding
101 // comment markers when splitting a line comment with a newline).
102 // 2) a selective clang-format run:
103 // - the "source code" passed to clang format is the code up to the cursor,
104 // a placeholder for the cursor, and some closing brackets
105 // - the formatting is restricted to the cursor and (possibly) other ranges
106 // (e.g. the old line when inserting a newline).
107 // - changes before the cursor are applied, those after are discarded.
108 struct IncrementalChanges {
109  // Changes that should be applied before running clang-format.
110  tooling::Replacements Changes;
111  // Ranges of the original source code that should be clang-formatted.
112  // The CursorProxyText will also be formatted.
113  std::vector<tooling::Range> FormatRanges;
114  // The source code that should stand in for the cursor when clang-formatting.
115  // e.g. after inserting a newline, a line-comment at the cursor is used to
116  // ensure that the newline is preserved.
117  std::string CursorPlaceholder;
118 };
119 
120 // After a newline:
121 // - we continue any line-comment that was split
122 // - we format the old line in addition to the cursor
123 // - we represent the cursor with a line comment to preserve the newline
124 IncrementalChanges getIncrementalChangesAfterNewline(llvm::StringRef Code,
125  unsigned Cursor) {
126  IncrementalChanges Result;
127  // Before newline, code looked like:
128  // leading^trailing
129  // After newline, code looks like:
130  // leading
131  // indentation^trailing
132  // Where indentation was added by the editor.
133  StringRef Trailing = firstLine(Code.substr(Cursor));
134  StringRef Indentation = lastLine(Code.take_front(Cursor));
135  if (Indentation.data() == Code.data()) {
136  vlog("Typed a newline, but we're still on the first line!");
137  return Result;
138  }
139  StringRef Leading =
140  lastLine(Code.take_front(Indentation.data() - Code.data() - 1));
141  StringRef NextLine = firstLine(Code.substr(Cursor + Trailing.size() + 1));
142 
143  // Strip leading whitespace on trailing line.
144  StringRef TrailingTrim = Trailing.ltrim();
145  if (unsigned TrailWS = Trailing.size() - TrailingTrim.size())
146  cantFail(Result.Changes.add(
147  replacement(Code, StringRef(Trailing.begin(), TrailWS), "")));
148 
149  // If we split a comment, replace indentation with a comment marker.
150  // If the editor made the new line a comment, also respect that.
151  StringRef CommentMarker = commentMarker(Leading);
152  bool NewLineIsComment = !commentMarker(Indentation).empty();
153  if (!CommentMarker.empty() &&
154  (NewLineIsComment || !commentMarker(NextLine).empty() ||
155  (!TrailingTrim.empty() && !TrailingTrim.startswith("//")))) {
156  using llvm::sys::unicode::columnWidthUTF8;
157  // We indent the new comment to match the previous one.
158  StringRef PreComment =
159  Leading.take_front(CommentMarker.data() - Leading.data());
160  std::string IndentAndComment =
161  (std::string(columnWidthUTF8(PreComment), ' ') + CommentMarker + " ")
162  .str();
163  cantFail(
164  Result.Changes.add(replacement(Code, Indentation, IndentAndComment)));
165  } else {
166  // Remove any indentation and let clang-format re-add it.
167  // This prevents the cursor marker dragging e.g. an aligned comment with it.
168  cantFail(Result.Changes.add(replacement(Code, Indentation, "")));
169  }
170 
171  // If we put a the newline inside a {} pair, put } on its own line...
172  if (CommentMarker.empty() && Leading.endswith("{") &&
173  Trailing.startswith("}")) {
174  cantFail(
175  Result.Changes.add(replacement(Code, Trailing.take_front(1), "\n}")));
176  // ...and format it.
177  Result.FormatRanges.push_back(
178  tooling::Range(Trailing.data() - Code.data() + 1, 1));
179  }
180 
181  // Format the whole leading line.
182  Result.FormatRanges.push_back(
183  tooling::Range(Leading.data() - Code.data(), Leading.size()));
184 
185  // We use a comment to represent the cursor, to preserve the newline.
186  // A trailing identifier improves parsing of e.g. for without braces.
187  // Exception: if the previous line has a trailing comment, we can't use one
188  // as the cursor (they will be aligned). But in this case we don't need to.
189  Result.CursorPlaceholder = !CommentMarker.empty() ? "ident" : "//==\nident";
190 
191  return Result;
192 }
193 
194 IncrementalChanges getIncrementalChanges(llvm::StringRef Code, unsigned Cursor,
195  llvm::StringRef InsertedText) {
196  IncrementalChanges Result;
197  if (InsertedText == "\n")
198  return getIncrementalChangesAfterNewline(Code, Cursor);
199 
200  Result.CursorPlaceholder = " /**/";
201  return Result;
202 }
203 
204 // Returns equivalent replacements that preserve the correspondence between
205 // OldCursor and NewCursor. If OldCursor lies in a replaced region, that
206 // replacement will be split.
207 std::vector<tooling::Replacement>
208 split(const tooling::Replacements &Replacements, unsigned OldCursor,
209  unsigned NewCursor) {
210  std::vector<tooling::Replacement> Result;
211  int LengthChange = 0;
212  for (const tooling::Replacement &R : Replacements) {
213  if (R.getOffset() + R.getLength() <= OldCursor) { // before cursor
214  Result.push_back(R);
215  LengthChange += R.getReplacementText().size() - R.getLength();
216  } else if (R.getOffset() < OldCursor) { // overlaps cursor
217  int ReplacementSplit = NewCursor - LengthChange - R.getOffset();
218  assert(ReplacementSplit >= 0 &&
219  ReplacementSplit <= int(R.getReplacementText().size()) &&
220  "NewCursor incompatible with OldCursor!");
221  Result.push_back(tooling::Replacement(
222  R.getFilePath(), R.getOffset(), OldCursor - R.getOffset(),
223  R.getReplacementText().take_front(ReplacementSplit)));
224  Result.push_back(tooling::Replacement(
225  R.getFilePath(), OldCursor,
226  R.getLength() - (OldCursor - R.getOffset()),
227  R.getReplacementText().drop_front(ReplacementSplit)));
228  } else if (R.getOffset() >= OldCursor) { // after cursor
229  Result.push_back(R);
230  }
231  }
232  return Result;
233 }
234 
235 } // namespace
236 
237 // We're simulating the following sequence of changes:
238 // - apply the pre-formatting edits (see getIncrementalChanges)
239 // - insert a placeholder for the cursor
240 // - format some of the resulting code
241 // - remove the cursor placeholder again
242 // The replacements we return are produced by composing these.
243 //
244 // The text we actually pass to clang-format is slightly different from this,
245 // e.g. we have to close brackets. We ensure these differences are *after*
246 // all the regions we want to format, and discard changes in them.
247 std::vector<tooling::Replacement>
248 formatIncremental(llvm::StringRef OriginalCode, unsigned OriginalCursor,
249  llvm::StringRef InsertedText, format::FormatStyle Style) {
250  IncrementalChanges Incremental =
251  getIncrementalChanges(OriginalCode, OriginalCursor, InsertedText);
252  // Never *remove* lines in response to pressing enter! This annoys users.
253  if (InsertedText == "\n") {
254  Style.MaxEmptyLinesToKeep = 1000;
255  Style.KeepEmptyLinesAtTheStartOfBlocks = true;
256  }
257 
258  // Compute the code we want to format:
259  // 1) Start with code after the pre-formatting edits.
260  std::string CodeToFormat = cantFail(
261  tooling::applyAllReplacements(OriginalCode, Incremental.Changes));
262  unsigned Cursor = Incremental.Changes.getShiftedCodePosition(OriginalCursor);
263  // 2) Truncate code after the last interesting range.
264  unsigned FormatLimit = Cursor;
265  for (tooling::Range &R : Incremental.FormatRanges)
266  FormatLimit = std::max(FormatLimit, R.getOffset() + R.getLength());
267  CodeToFormat.resize(FormatLimit);
268  // 3) Insert a placeholder for the cursor.
269  CodeToFormat.insert(Cursor, Incremental.CursorPlaceholder);
270  // 4) Append brackets after FormatLimit so the code is well-formed.
271  closeBrackets(CodeToFormat, Style);
272 
273  // Determine the ranges to format:
274  std::vector<tooling::Range> RangesToFormat = Incremental.FormatRanges;
275  // Ranges after the cursor need to be adjusted for the placeholder.
276  for (auto &R : RangesToFormat) {
277  if (R.getOffset() > Cursor)
278  R = tooling::Range(R.getOffset() + Incremental.CursorPlaceholder.size(),
279  R.getLength());
280  }
281  // We also format the cursor.
282  RangesToFormat.push_back(
283  tooling::Range(Cursor, Incremental.CursorPlaceholder.size()));
284  // Also update FormatLimit for the placeholder, we'll use this later.
285  FormatLimit += Incremental.CursorPlaceholder.size();
286 
287  // Run clang-format, and truncate changes at FormatLimit.
288  tooling::Replacements FormattingChanges;
289  format::FormattingAttemptStatus Status;
290  for (const tooling::Replacement &R : format::reformat(
291  Style, CodeToFormat, RangesToFormat, Filename, &Status)) {
292  if (R.getOffset() + R.getLength() <= FormatLimit) // Before limit.
293  cantFail(FormattingChanges.add(R));
294  else if(R.getOffset() < FormatLimit) { // Overlaps limit.
295  if (R.getReplacementText().empty()) // Deletions are easy to handle.
296  cantFail(FormattingChanges.add(tooling::Replacement(Filename,
297  R.getOffset(), FormatLimit - R.getOffset(), "")));
298  else
299  // Hopefully won't happen in practice?
300  elog("Incremental clang-format edit overlapping cursor @ {0}!\n{1}",
301  Cursor, CodeToFormat);
302  }
303  }
304  if (!Status.FormatComplete)
305  vlog("Incremental format incomplete at line {0}", Status.Line);
306 
307  // Now we are ready to compose the changes relative to OriginalCode.
308  // edits -> insert placeholder -> format -> remove placeholder.
309  // We must express insert/remove as Replacements.
310  tooling::Replacements InsertCursorPlaceholder(
311  tooling::Replacement(Filename, Cursor, 0, Incremental.CursorPlaceholder));
312  unsigned FormattedCursorStart =
313  FormattingChanges.getShiftedCodePosition(Cursor),
314  FormattedCursorEnd = FormattingChanges.getShiftedCodePosition(
315  Cursor + Incremental.CursorPlaceholder.size());
316  tooling::Replacements RemoveCursorPlaceholder(
317  tooling::Replacement(Filename, FormattedCursorStart,
318  FormattedCursorEnd - FormattedCursorStart, ""));
319 
320  // We can't simply merge() and return: tooling::Replacements will combine
321  // adjacent edits left and right of the cursor. This gives the right source
322  // code, but loses information about where the cursor is!
323  // Fortunately, none of the individual passes lose information, so:
324  // - we use merge() to compute the final Replacements
325  // - we chain getShiftedCodePosition() to compute final cursor position
326  // - we split the final Replacements at the cursor position, so that
327  // each Replacement lies either before or after the cursor.
328  tooling::Replacements Final;
329  unsigned FinalCursor = OriginalCursor;
330 #ifndef NDEBUG
331  std::string FinalCode = std::string(OriginalCode);
332  dlog("Initial code: {0}", FinalCode);
333 #endif
334  for (auto Pass :
335  std::vector<std::pair<const char *, const tooling::Replacements *>>{
336  {"Pre-formatting changes", &Incremental.Changes},
337  {"Insert placeholder", &InsertCursorPlaceholder},
338  {"clang-format", &FormattingChanges},
339  {"Remove placeholder", &RemoveCursorPlaceholder}}) {
340  Final = Final.merge(*Pass.second);
341  FinalCursor = Pass.second->getShiftedCodePosition(FinalCursor);
342 #ifndef NDEBUG
343  FinalCode =
344  cantFail(tooling::applyAllReplacements(FinalCode, *Pass.second));
345  dlog("After {0}:\n{1}^{2}", Pass.first,
346  StringRef(FinalCode).take_front(FinalCursor),
347  StringRef(FinalCode).drop_front(FinalCursor));
348 #endif
349  }
350  return split(Final, OriginalCursor, FinalCursor);
351 }
352 
353 unsigned
355  const std::vector<tooling::Replacement> &Replacements) {
356  unsigned OriginalOffset = Offset;
357  for (const auto &R : Replacements) {
358  if (R.getOffset() + R.getLength() <= OriginalOffset) {
359  // Replacement is before cursor.
360  Offset += R.getReplacementText().size();
361  Offset -= R.getLength();
362  } else if (R.getOffset() < OriginalOffset) {
363  // Replacement overlaps cursor.
364  // Preserve position within replacement text, as far as possible.
365  unsigned PositionWithinReplacement = Offset - R.getOffset();
366  if (PositionWithinReplacement > R.getReplacementText().size()) {
367  Offset += R.getReplacementText().size();
368  Offset -= PositionWithinReplacement;
369  }
370  } else {
371  // Replacement after cursor.
372  break; // Replacements are sorted, the rest are also after the cursor.
373  }
374  }
375  return Offset;
376 }
377 
378 } // namespace clangd
379 } // namespace clang
dlog
#define dlog(...)
Definition: Logger.h:102
FormatRanges
std::vector< tooling::Range > FormatRanges
Definition: Format.cpp:113
Range
CharSourceRange Range
SourceRange for the file name.
Definition: IncludeOrderCheck.cpp:38
CursorPlaceholder
std::string CursorPlaceholder
Definition: Format.cpp:117
FormatStyle
static cl::opt< std::string > FormatStyle("format-style", cl::desc(R"( Style for formatting code around applied fixes: - 'none' (default) turns off formatting - 'file' (literally 'file', not a placeholder) uses .clang-format file in the closest parent directory - '{ <json> }' specifies options inline, e.g. -format-style='{BasedOnStyle: llvm, IndentWidth: 8}' - 'llvm', 'google', 'webkit', 'mozilla' See clang-format documentation for the up-to-date information about formatting styles and options. This option overrides the 'FormatStyle` option in .clang-tidy file, if any. )"), cl::init("none"), cl::cat(ClangTidyCategory))
Filename
std::string Filename
Filename as a string.
Definition: IncludeOrderCheck.cpp:39
Format.h
Changes
tooling::Replacements Changes
Definition: Format.cpp:110
Offset
size_t Offset
Definition: CodeComplete.cpp:1173
Code
std::string Code
Definition: FindTargetTests.cpp:67
Line
int Line
Definition: PreprocessorTracker.cpp:514
Logger.h
clang::clangd::vlog
void vlog(const char *Fmt, Ts &&... Vals)
Definition: Logger.h:73
clang::clangd::TextDocumentSyncKind::Incremental
@ Incremental
Documents are synced by sending the full content on open.
clang::clangd::transformCursorPosition
unsigned transformCursorPosition(unsigned Offset, const std::vector< tooling::Replacement > &Replacements)
Determine the new cursor position after applying Replacements.
Definition: Format.cpp:354
C
const Criteria C
Definition: FunctionCognitiveComplexityCheck.cpp:93
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
clang::clangd::formatIncremental
std::vector< tooling::Replacement > formatIncremental(llvm::StringRef OriginalCode, unsigned OriginalCursor, llvm::StringRef InsertedText, format::FormatStyle Style)
Applies limited formatting around new InsertedText.
Definition: Format.cpp:248
SM
const SourceManager & SM
Definition: IncludeCleaner.cpp:140
clang::clangd::elog
void elog(const char *Fmt, Ts &&... Vals)
Definition: Logger.h:62