clang-tools  11.0.0
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("dummy.cpp", Code);
27  auto &SM = FileSM.get();
28  FileID FID = SM.getMainFileID();
29  Lexer Lex(FID, SM.getBuffer(FID), SM, format::getFormattingLangOpts(Style));
30  Token Tok;
31  std::vector<char> Brackets;
32  while (!Lex.LexFromRawLexer(Tok)) {
33  switch(Tok.getKind()) {
34  case tok::l_paren:
35  Brackets.push_back(')');
36  break;
37  case tok::l_brace:
38  Brackets.push_back('}');
39  break;
40  case tok::l_square:
41  Brackets.push_back(']');
42  break;
43  case tok::r_paren:
44  if (!Brackets.empty() && Brackets.back() == ')')
45  Brackets.pop_back();
46  break;
47  case tok::r_brace:
48  if (!Brackets.empty() && Brackets.back() == '}')
49  Brackets.pop_back();
50  break;
51  case tok::r_square:
52  if (!Brackets.empty() && Brackets.back() == ']')
53  Brackets.pop_back();
54  break;
55  default:
56  continue;
57  }
58  }
59  // Attempt to end any open comments first.
60  Code.append("\n// */\n");
61  Code.append(Brackets.rbegin(), Brackets.rend());
62 }
63 
64 static StringRef commentMarker(llvm::StringRef Line) {
65  for (StringRef Marker : {"///", "//"}){
66  auto I = Line.rfind(Marker);
67  if (I != StringRef::npos)
68  return Line.substr(I, Marker.size());
69  }
70  return "";
71 }
72 
73 llvm::StringRef firstLine(llvm::StringRef Code) {
74  return Code.take_until([](char C) { return C == '\n'; });
75 }
76 
77 llvm::StringRef lastLine(llvm::StringRef Code) {
78  llvm::StringRef Rest = Code;
79  while (!Rest.empty() && Rest.back() != '\n')
80  Rest = Rest.drop_back();
81  return Code.substr(Rest.size());
82 }
83 
84 // Filename is needed for tooling::Replacement and some overloads of reformat().
85 // Its value should not affect the outcome. We use the default from reformat().
86 llvm::StringRef Filename = "<stdin>";
87 
88 // tooling::Replacement from overlapping StringRefs: From must be part of Code.
89 tooling::Replacement replacement(llvm::StringRef Code, llvm::StringRef From,
90  llvm::StringRef To) {
91  assert(From.begin() >= Code.begin() && From.end() <= Code.end());
92  // The filename is required but ignored.
93  return tooling::Replacement(Filename, From.data() - Code.data(),
94  From.size(), To);
95 }
96 
97 // High-level representation of incremental formatting changes.
98 // The changes are made in two steps.
99 // 1) a (possibly-empty) set of changes synthesized by clangd (e.g. adding
100 // comment markers when splitting a line comment with a newline).
101 // 2) a selective clang-format run:
102 // - the "source code" passed to clang format is the code up to the cursor,
103 // a placeholder for the cursor, and some closing brackets
104 // - the formatting is restricted to the cursor and (possibly) other ranges
105 // (e.g. the old line when inserting a newline).
106 // - changes before the cursor are applied, those after are discarded.
107 struct IncrementalChanges {
108  // Changes that should be applied before running clang-format.
109  tooling::Replacements Changes;
110  // Ranges of the original source code that should be clang-formatted.
111  // The CursorProxyText will also be formatted.
112  std::vector<tooling::Range> FormatRanges;
113  // The source code that should stand in for the cursor when clang-formatting.
114  // e.g. after inserting a newline, a line-comment at the cursor is used to
115  // ensure that the newline is preserved.
116  std::string CursorPlaceholder;
117 };
118 
119 // After a newline:
120 // - we continue any line-comment that was split
121 // - we format the old line in addition to the cursor
122 // - we represent the cursor with a line comment to preserve the newline
123 IncrementalChanges getIncrementalChangesAfterNewline(llvm::StringRef Code,
124  unsigned Cursor) {
125  IncrementalChanges Result;
126  // Before newline, code looked like:
127  // leading^trailing
128  // After newline, code looks like:
129  // leading
130  // indentation^trailing
131  // Where indentation was added by the editor.
132  StringRef Trailing = firstLine(Code.substr(Cursor));
133  StringRef Indentation = lastLine(Code.take_front(Cursor));
134  if (Indentation.data() == Code.data()) {
135  vlog("Typed a newline, but we're still on the first line!");
136  return Result;
137  }
138  StringRef Leading =
139  lastLine(Code.take_front(Indentation.data() - Code.data() - 1));
140  StringRef NextLine = firstLine(Code.substr(Cursor + Trailing.size() + 1));
141 
142  // Strip leading whitespace on trailing line.
143  StringRef TrailingTrim = Trailing.ltrim();
144  if (unsigned TrailWS = Trailing.size() - TrailingTrim.size())
145  cantFail(Result.Changes.add(
146  replacement(Code, StringRef(Trailing.begin(), TrailWS), "")));
147 
148  // If we split a comment, replace indentation with a comment marker.
149  // If the editor made the new line a comment, also respect that.
150  StringRef CommentMarker = commentMarker(Leading);
151  bool NewLineIsComment = !commentMarker(Indentation).empty();
152  if (!CommentMarker.empty() &&
153  (NewLineIsComment || !commentMarker(NextLine).empty() ||
154  (!TrailingTrim.empty() && !TrailingTrim.startswith("//")))) {
155  using llvm::sys::unicode::columnWidthUTF8;
156  // We indent the new comment to match the previous one.
157  StringRef PreComment =
158  Leading.take_front(CommentMarker.data() - Leading.data());
159  std::string IndentAndComment =
160  (std::string(columnWidthUTF8(PreComment), ' ') + CommentMarker + " ")
161  .str();
162  cantFail(
163  Result.Changes.add(replacement(Code, Indentation, IndentAndComment)));
164  } else {
165  // Remove any indentation and let clang-format re-add it.
166  // This prevents the cursor marker dragging e.g. an aligned comment with it.
167  cantFail(Result.Changes.add(replacement(Code, Indentation, "")));
168  }
169 
170  // If we put a the newline inside a {} pair, put } on its own line...
171  if (CommentMarker.empty() && Leading.endswith("{") &&
172  Trailing.startswith("}")) {
173  cantFail(
174  Result.Changes.add(replacement(Code, Trailing.take_front(1), "\n}")));
175  // ...and format it.
176  Result.FormatRanges.push_back(
177  tooling::Range(Trailing.data() - Code.data() + 1, 1));
178  }
179 
180  // Format the whole leading line.
181  Result.FormatRanges.push_back(
182  tooling::Range(Leading.data() - Code.data(), Leading.size()));
183 
184  // We use a comment to represent the cursor, to preserve the newline.
185  // A trailing identifier improves parsing of e.g. for without braces.
186  // Exception: if the previous line has a trailing comment, we can't use one
187  // as the cursor (they will be aligned). But in this case we don't need to.
188  Result.CursorPlaceholder = !CommentMarker.empty() ? "ident" : "//==\nident";
189 
190  return Result;
191 }
192 
193 IncrementalChanges getIncrementalChanges(llvm::StringRef Code, unsigned Cursor,
194  llvm::StringRef InsertedText) {
195  IncrementalChanges Result;
196  if (InsertedText == "\n")
197  return getIncrementalChangesAfterNewline(Code, Cursor);
198 
199  Result.CursorPlaceholder = " /**/";
200  return Result;
201 }
202 
203 // Returns equivalent replacements that preserve the correspondence between
204 // OldCursor and NewCursor. If OldCursor lies in a replaced region, that
205 // replacement will be split.
206 std::vector<tooling::Replacement>
207 split(const tooling::Replacements &Replacements, unsigned OldCursor,
208  unsigned NewCursor) {
209  std::vector<tooling::Replacement> Result;
210  int LengthChange = 0;
211  for (const tooling::Replacement &R : Replacements) {
212  if (R.getOffset() + R.getLength() <= OldCursor) { // before cursor
213  Result.push_back(R);
214  LengthChange += R.getReplacementText().size() - R.getLength();
215  } else if (R.getOffset() < OldCursor) { // overlaps cursor
216  int ReplacementSplit = NewCursor - LengthChange - R.getOffset();
217  assert(ReplacementSplit >= 0 &&
218  ReplacementSplit <= int(R.getReplacementText().size()) &&
219  "NewCursor incompatible with OldCursor!");
220  Result.push_back(tooling::Replacement(
221  R.getFilePath(), R.getOffset(), OldCursor - R.getOffset(),
222  R.getReplacementText().take_front(ReplacementSplit)));
223  Result.push_back(tooling::Replacement(
224  R.getFilePath(), OldCursor,
225  R.getLength() - (OldCursor - R.getOffset()),
226  R.getReplacementText().drop_front(ReplacementSplit)));
227  } else if (R.getOffset() >= OldCursor) { // after cursor
228  Result.push_back(R);
229  }
230  }
231  return Result;
232 }
233 
234 } // namespace
235 
236 // We're simulating the following sequence of changes:
237 // - apply the pre-formatting edits (see getIncrementalChanges)
238 // - insert a placeholder for the cursor
239 // - format some of the resulting code
240 // - remove the cursor placeholder again
241 // The replacements we return are produced by composing these.
242 //
243 // The text we actually pass to clang-format is slightly different from this,
244 // e.g. we have to close brackets. We ensure these differences are *after*
245 // all the regions we want to format, and discard changes in them.
246 std::vector<tooling::Replacement>
247 formatIncremental(llvm::StringRef OriginalCode, unsigned OriginalCursor,
248  llvm::StringRef InsertedText, format::FormatStyle Style) {
249  IncrementalChanges Incremental =
250  getIncrementalChanges(OriginalCode, OriginalCursor, InsertedText);
251  // Never *remove* lines in response to pressing enter! This annoys users.
252  if (InsertedText == "\n") {
253  Style.MaxEmptyLinesToKeep = 1000;
254  Style.KeepEmptyLinesAtTheStartOfBlocks = true;
255  }
256 
257  // Compute the code we want to format:
258  // 1) Start with code after the pre-formatting edits.
259  std::string CodeToFormat = cantFail(
260  tooling::applyAllReplacements(OriginalCode, Incremental.Changes));
261  unsigned Cursor = Incremental.Changes.getShiftedCodePosition(OriginalCursor);
262  // 2) Truncate code after the last interesting range.
263  unsigned FormatLimit = Cursor;
264  for (tooling::Range &R : Incremental.FormatRanges)
265  FormatLimit = std::max(FormatLimit, R.getOffset() + R.getLength());
266  CodeToFormat.resize(FormatLimit);
267  // 3) Insert a placeholder for the cursor.
268  CodeToFormat.insert(Cursor, Incremental.CursorPlaceholder);
269  // 4) Append brackets after FormatLimit so the code is well-formed.
270  closeBrackets(CodeToFormat, Style);
271 
272  // Determine the ranges to format:
273  std::vector<tooling::Range> RangesToFormat = Incremental.FormatRanges;
274  // Ranges after the cursor need to be adjusted for the placeholder.
275  for (auto &R : RangesToFormat) {
276  if (R.getOffset() > Cursor)
277  R = tooling::Range(R.getOffset() + Incremental.CursorPlaceholder.size(),
278  R.getLength());
279  }
280  // We also format the cursor.
281  RangesToFormat.push_back(
282  tooling::Range(Cursor, Incremental.CursorPlaceholder.size()));
283  // Also update FormatLimit for the placeholder, we'll use this later.
284  FormatLimit += Incremental.CursorPlaceholder.size();
285 
286  // Run clang-format, and truncate changes at FormatLimit.
287  tooling::Replacements FormattingChanges;
288  format::FormattingAttemptStatus Status;
289  for (const tooling::Replacement &R : format::reformat(
290  Style, CodeToFormat, RangesToFormat, Filename, &Status)) {
291  if (R.getOffset() + R.getLength() <= FormatLimit) // Before limit.
292  cantFail(FormattingChanges.add(R));
293  else if(R.getOffset() < FormatLimit) { // Overlaps limit.
294  if (R.getReplacementText().empty()) // Deletions are easy to handle.
295  cantFail(FormattingChanges.add(tooling::Replacement(Filename,
296  R.getOffset(), FormatLimit - R.getOffset(), "")));
297  else
298  // Hopefully won't happen in practice?
299  elog("Incremental clang-format edit overlapping cursor @ {0}!\n{1}",
300  Cursor, CodeToFormat);
301  }
302  }
303  if (!Status.FormatComplete)
304  vlog("Incremental format incomplete at line {0}", Status.Line);
305 
306  // Now we are ready to compose the changes relative to OriginalCode.
307  // edits -> insert placeholder -> format -> remove placeholder.
308  // We must express insert/remove as Replacements.
309  tooling::Replacements InsertCursorPlaceholder(
310  tooling::Replacement(Filename, Cursor, 0, Incremental.CursorPlaceholder));
311  unsigned FormattedCursorStart =
312  FormattingChanges.getShiftedCodePosition(Cursor),
313  FormattedCursorEnd = FormattingChanges.getShiftedCodePosition(
314  Cursor + Incremental.CursorPlaceholder.size());
315  tooling::Replacements RemoveCursorPlaceholder(
316  tooling::Replacement(Filename, FormattedCursorStart,
317  FormattedCursorEnd - FormattedCursorStart, ""));
318 
319  // We can't simply merge() and return: tooling::Replacements will combine
320  // adjacent edits left and right of the cursor. This gives the right source
321  // code, but loses information about where the cursor is!
322  // Fortunately, none of the individual passes lose information, so:
323  // - we use merge() to compute the final Replacements
324  // - we chain getShiftedCodePosition() to compute final cursor position
325  // - we split the final Replacements at the cursor position, so that
326  // each Replacement lies either before or after the cursor.
327  tooling::Replacements Final;
328  unsigned FinalCursor = OriginalCursor;
329 #ifndef NDEBUG
330  std::string FinalCode = std::string(OriginalCode);
331  dlog("Initial code: {0}", FinalCode);
332 #endif
333  for (auto Pass :
334  std::vector<std::pair<const char *, const tooling::Replacements *>>{
335  {"Pre-formatting changes", &Incremental.Changes},
336  {"Insert placeholder", &InsertCursorPlaceholder},
337  {"clang-format", &FormattingChanges},
338  {"Remove placeholder", &RemoveCursorPlaceholder}}) {
339  Final = Final.merge(*Pass.second);
340  FinalCursor = Pass.second->getShiftedCodePosition(FinalCursor);
341 #ifndef NDEBUG
342  FinalCode =
343  cantFail(tooling::applyAllReplacements(FinalCode, *Pass.second));
344  dlog("After {0}:\n{1}^{2}", Pass.first,
345  StringRef(FinalCode).take_front(FinalCursor),
346  StringRef(FinalCode).drop_front(FinalCursor));
347 #endif
348  }
349  return split(Final, OriginalCursor, FinalCursor);
350 }
351 
352 unsigned
354  const std::vector<tooling::Replacement> &Replacements) {
355  unsigned OriginalOffset = Offset;
356  for (const auto &R : Replacements) {
357  if (R.getOffset() + R.getLength() <= OriginalOffset) {
358  // Replacement is before cursor.
359  Offset += R.getReplacementText().size();
360  Offset -= R.getLength();
361  } else if (R.getOffset() < OriginalOffset) {
362  // Replacement overlaps cursor.
363  // Preserve position within replacement text, as far as possible.
364  unsigned PositionWithinReplacement = Offset - R.getOffset();
365  if (PositionWithinReplacement > R.getReplacementText().size()) {
366  Offset += R.getReplacementText().size();
367  Offset -= PositionWithinReplacement;
368  }
369  } else {
370  // Replacement after cursor.
371  break; // Replacements are sorted, the rest are also after the cursor.
372  }
373  }
374  return Offset;
375 }
376 
377 } // namespace clangd
378 } // namespace clang
dlog
#define dlog(...)
Definition: Logger.h:72
FormatRanges
std::vector< tooling::Range > FormatRanges
Definition: Format.cpp:112
Range
CharSourceRange Range
SourceRange for the file name.
Definition: IncludeOrderCheck.cpp:38
CursorPlaceholder
std::string CursorPlaceholder
Definition: Format.cpp:116
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:109
Offset
size_t Offset
Definition: CodeComplete.cpp:1044
Code
std::string Code
Definition: FindTargetTests.cpp:67
Line
int Line
Definition: PreprocessorTracker.cpp:513
Logger.h
clang::clangd::vlog
void vlog(const char *Fmt, Ts &&... Vals)
Definition: Logger.h:67
clang::clangd::TextDocumentSyncKind::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:353
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:247
clang::clangd::elog
void elog(const char *Fmt, Ts &&... Vals)
Definition: Logger.h:56