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//===--- Format.cpp -----------------------------------------*- C++-*------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "Format.h"
#include "support/Logger.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Format/Format.h"
#include "clang/Lex/Lexer.h"
#include "clang/Tooling/Core/Replacement.h"
#include "llvm/Support/Unicode.h"
namespace clang {
namespace clangd {
namespace {
/// Append closing brackets )]} to \p Code to make it well-formed.
/// Clang-format conservatively refuses to format files with unmatched brackets
/// as it isn't sure where the errors are and so can't correct.
/// When editing, it's reasonable to assume code before the cursor is complete.
void closeBrackets(std::string &Code, const format::FormatStyle &Style) {
SourceManagerForFile FileSM("mock_file.cpp", Code);
auto &SM = FileSM.get();
FileID FID = SM.getMainFileID();
Lexer Lex(FID, SM.getBufferOrFake(FID), SM,
format::getFormattingLangOpts(Style));
Token Tok;
std::vector<char> Brackets;
while (!Lex.LexFromRawLexer(Tok)) {
switch(Tok.getKind()) {
case tok::l_paren:
Brackets.push_back(')');
break;
case tok::l_brace:
Brackets.push_back('}');
break;
case tok::l_square:
Brackets.push_back(']');
break;
case tok::r_paren:
if (!Brackets.empty() && Brackets.back() == ')')
Brackets.pop_back();
break;
case tok::r_brace:
if (!Brackets.empty() && Brackets.back() == '}')
Brackets.pop_back();
break;
case tok::r_square:
if (!Brackets.empty() && Brackets.back() == ']')
Brackets.pop_back();
break;
default:
continue;
}
}
// Attempt to end any open comments first.
Code.append("\n// */\n");
Code.append(Brackets.rbegin(), Brackets.rend());
}
static StringRef commentMarker(llvm::StringRef Line) {
for (StringRef Marker : {"///", "//"}){
auto I = Line.rfind(Marker);
if (I != StringRef::npos)
return Line.substr(I, Marker.size());
}
return "";
}
llvm::StringRef firstLine(llvm::StringRef Code) {
return Code.take_until([](char C) { return C == '\n'; });
}
llvm::StringRef lastLine(llvm::StringRef Code) {
llvm::StringRef Rest = Code;
while (!Rest.empty() && Rest.back() != '\n')
Rest = Rest.drop_back();
return Code.substr(Rest.size());
}
// Filename is needed for tooling::Replacement and some overloads of reformat().
// Its value should not affect the outcome. We use the default from reformat().
llvm::StringRef Filename = "<stdin>";
// tooling::Replacement from overlapping StringRefs: From must be part of Code.
tooling::Replacement replacement(llvm::StringRef Code, llvm::StringRef From,
llvm::StringRef To) {
assert(From.begin() >= Code.begin() && From.end() <= Code.end());
// The filename is required but ignored.
return tooling::Replacement(Filename, From.data() - Code.data(),
From.size(), To);
}
// High-level representation of incremental formatting changes.
// The changes are made in two steps.
// 1) a (possibly-empty) set of changes synthesized by clangd (e.g. adding
// comment markers when splitting a line comment with a newline).
// 2) a selective clang-format run:
// - the "source code" passed to clang format is the code up to the cursor,
// a placeholder for the cursor, and some closing brackets
// - the formatting is restricted to the cursor and (possibly) other ranges
// (e.g. the old line when inserting a newline).
// - changes before the cursor are applied, those after are discarded.
struct IncrementalChanges {
// Changes that should be applied before running clang-format.
tooling::Replacements Changes;
// Ranges of the original source code that should be clang-formatted.
// The CursorProxyText will also be formatted.
std::vector<tooling::Range> FormatRanges;
// The source code that should stand in for the cursor when clang-formatting.
// e.g. after inserting a newline, a line-comment at the cursor is used to
// ensure that the newline is preserved.
std::string CursorPlaceholder;
};
// After a newline:
// - we continue any line-comment that was split
// - we format the old line in addition to the cursor
// - we represent the cursor with a line comment to preserve the newline
IncrementalChanges getIncrementalChangesAfterNewline(llvm::StringRef Code,
unsigned Cursor) {
IncrementalChanges Result;
// Before newline, code looked like:
// leading^trailing
// After newline, code looks like:
// leading
// indentation^trailing
// Where indentation was added by the editor.
StringRef Trailing = firstLine(Code.substr(Cursor));
StringRef Indentation = lastLine(Code.take_front(Cursor));
if (Indentation.data() == Code.data()) {
vlog("Typed a newline, but we're still on the first line!");
return Result;
}
StringRef Leading =
lastLine(Code.take_front(Indentation.data() - Code.data() - 1));
StringRef NextLine = firstLine(Code.substr(Cursor + Trailing.size() + 1));
// Strip leading whitespace on trailing line.
StringRef TrailingTrim = Trailing.ltrim();
if (unsigned TrailWS = Trailing.size() - TrailingTrim.size())
cantFail(Result.Changes.add(
replacement(Code, StringRef(Trailing.begin(), TrailWS), "")));
// If we split a comment, replace indentation with a comment marker.
// If the editor made the new line a comment, also respect that.
StringRef CommentMarker = commentMarker(Leading);
bool NewLineIsComment = !commentMarker(Indentation).empty();
if (!CommentMarker.empty() &&
(NewLineIsComment || !commentMarker(NextLine).empty() ||
(!TrailingTrim.empty() && !TrailingTrim.startswith("//")))) {
using llvm::sys::unicode::columnWidthUTF8;
// We indent the new comment to match the previous one.
StringRef PreComment =
Leading.take_front(CommentMarker.data() - Leading.data());
std::string IndentAndComment =
(std::string(columnWidthUTF8(PreComment), ' ') + CommentMarker + " ")
.str();
cantFail(
Result.Changes.add(replacement(Code, Indentation, IndentAndComment)));
} else {
// Remove any indentation and let clang-format re-add it.
// This prevents the cursor marker dragging e.g. an aligned comment with it.
cantFail(Result.Changes.add(replacement(Code, Indentation, "")));
}
// If we put a the newline inside a {} pair, put } on its own line...
if (CommentMarker.empty() && Leading.endswith("{") &&
Trailing.startswith("}")) {
cantFail(
Result.Changes.add(replacement(Code, Trailing.take_front(1), "\n}")));
// ...and format it.
Result.FormatRanges.push_back(
tooling::Range(Trailing.data() - Code.data() + 1, 1));
}
// Format the whole leading line.
Result.FormatRanges.push_back(
tooling::Range(Leading.data() - Code.data(), Leading.size()));
// We use a comment to represent the cursor, to preserve the newline.
// A trailing identifier improves parsing of e.g. for without braces.
// Exception: if the previous line has a trailing comment, we can't use one
// as the cursor (they will be aligned). But in this case we don't need to.
Result.CursorPlaceholder = !CommentMarker.empty() ? "ident" : "//==\nident";
return Result;
}
IncrementalChanges getIncrementalChanges(llvm::StringRef Code, unsigned Cursor,
llvm::StringRef InsertedText) {
IncrementalChanges Result;
if (InsertedText == "\n")
return getIncrementalChangesAfterNewline(Code, Cursor);
Result.CursorPlaceholder = " /**/";
return Result;
}
// Returns equivalent replacements that preserve the correspondence between
// OldCursor and NewCursor. If OldCursor lies in a replaced region, that
// replacement will be split.
std::vector<tooling::Replacement>
split(const tooling::Replacements &Replacements, unsigned OldCursor,
unsigned NewCursor) {
std::vector<tooling::Replacement> Result;
int LengthChange = 0;
for (const tooling::Replacement &R : Replacements) {
if (R.getOffset() + R.getLength() <= OldCursor) { // before cursor
Result.push_back(R);
LengthChange += R.getReplacementText().size() - R.getLength();
} else if (R.getOffset() < OldCursor) { // overlaps cursor
int ReplacementSplit = NewCursor - LengthChange - R.getOffset();
assert(ReplacementSplit >= 0 &&
ReplacementSplit <= int(R.getReplacementText().size()) &&
"NewCursor incompatible with OldCursor!");
Result.push_back(tooling::Replacement(
R.getFilePath(), R.getOffset(), OldCursor - R.getOffset(),
R.getReplacementText().take_front(ReplacementSplit)));
Result.push_back(tooling::Replacement(
R.getFilePath(), OldCursor,
R.getLength() - (OldCursor - R.getOffset()),
R.getReplacementText().drop_front(ReplacementSplit)));
} else if (R.getOffset() >= OldCursor) { // after cursor
Result.push_back(R);
}
}
return Result;
}
} // namespace
// We're simulating the following sequence of changes:
// - apply the pre-formatting edits (see getIncrementalChanges)
// - insert a placeholder for the cursor
// - format some of the resulting code
// - remove the cursor placeholder again
// The replacements we return are produced by composing these.
//
// The text we actually pass to clang-format is slightly different from this,
// e.g. we have to close brackets. We ensure these differences are *after*
// all the regions we want to format, and discard changes in them.
std::vector<tooling::Replacement>
formatIncremental(llvm::StringRef OriginalCode, unsigned OriginalCursor,
llvm::StringRef InsertedText, format::FormatStyle Style) {
IncrementalChanges Incremental =
getIncrementalChanges(OriginalCode, OriginalCursor, InsertedText);
// Never *remove* lines in response to pressing enter! This annoys users.
if (InsertedText == "\n") {
Style.MaxEmptyLinesToKeep = 1000;
Style.KeepEmptyLinesAtTheStartOfBlocks = true;
}
// Compute the code we want to format:
// 1) Start with code after the pre-formatting edits.
std::string CodeToFormat = cantFail(
tooling::applyAllReplacements(OriginalCode, Incremental.Changes));
unsigned Cursor = Incremental.Changes.getShiftedCodePosition(OriginalCursor);
// 2) Truncate code after the last interesting range.
unsigned FormatLimit = Cursor;
for (tooling::Range &R : Incremental.FormatRanges)
FormatLimit = std::max(FormatLimit, R.getOffset() + R.getLength());
CodeToFormat.resize(FormatLimit);
// 3) Insert a placeholder for the cursor.
CodeToFormat.insert(Cursor, Incremental.CursorPlaceholder);
// 4) Append brackets after FormatLimit so the code is well-formed.
closeBrackets(CodeToFormat, Style);
// Determine the ranges to format:
std::vector<tooling::Range> RangesToFormat = Incremental.FormatRanges;
// Ranges after the cursor need to be adjusted for the placeholder.
for (auto &R : RangesToFormat) {
if (R.getOffset() > Cursor)
R = tooling::Range(R.getOffset() + Incremental.CursorPlaceholder.size(),
R.getLength());
}
// We also format the cursor.
RangesToFormat.push_back(
tooling::Range(Cursor, Incremental.CursorPlaceholder.size()));
// Also update FormatLimit for the placeholder, we'll use this later.
FormatLimit += Incremental.CursorPlaceholder.size();
// Run clang-format, and truncate changes at FormatLimit.
tooling::Replacements FormattingChanges;
format::FormattingAttemptStatus Status;
for (const tooling::Replacement &R : format::reformat(
Style, CodeToFormat, RangesToFormat, Filename, &Status)) {
if (R.getOffset() + R.getLength() <= FormatLimit) // Before limit.
cantFail(FormattingChanges.add(R));
else if(R.getOffset() < FormatLimit) { // Overlaps limit.
if (R.getReplacementText().empty()) // Deletions are easy to handle.
cantFail(FormattingChanges.add(tooling::Replacement(Filename,
R.getOffset(), FormatLimit - R.getOffset(), "")));
else
// Hopefully won't happen in practice?
elog("Incremental clang-format edit overlapping cursor @ {0}!\n{1}",
Cursor, CodeToFormat);
}
}
if (!Status.FormatComplete)
vlog("Incremental format incomplete at line {0}", Status.Line);
// Now we are ready to compose the changes relative to OriginalCode.
// edits -> insert placeholder -> format -> remove placeholder.
// We must express insert/remove as Replacements.
tooling::Replacements InsertCursorPlaceholder(
tooling::Replacement(Filename, Cursor, 0, Incremental.CursorPlaceholder));
unsigned FormattedCursorStart =
FormattingChanges.getShiftedCodePosition(Cursor),
FormattedCursorEnd = FormattingChanges.getShiftedCodePosition(
Cursor + Incremental.CursorPlaceholder.size());
tooling::Replacements RemoveCursorPlaceholder(
tooling::Replacement(Filename, FormattedCursorStart,
FormattedCursorEnd - FormattedCursorStart, ""));
// We can't simply merge() and return: tooling::Replacements will combine
// adjacent edits left and right of the cursor. This gives the right source
// code, but loses information about where the cursor is!
// Fortunately, none of the individual passes lose information, so:
// - we use merge() to compute the final Replacements
// - we chain getShiftedCodePosition() to compute final cursor position
// - we split the final Replacements at the cursor position, so that
// each Replacement lies either before or after the cursor.
tooling::Replacements Final;
unsigned FinalCursor = OriginalCursor;
#ifndef NDEBUG
std::string FinalCode = std::string(OriginalCode);
dlog("Initial code: {0}", FinalCode);
#endif
for (auto Pass :
std::vector<std::pair<const char *, const tooling::Replacements *>>{
{"Pre-formatting changes", &Incremental.Changes},
{"Insert placeholder", &InsertCursorPlaceholder},
{"clang-format", &FormattingChanges},
{"Remove placeholder", &RemoveCursorPlaceholder}}) {
Final = Final.merge(*Pass.second);
FinalCursor = Pass.second->getShiftedCodePosition(FinalCursor);
#ifndef NDEBUG
FinalCode =
cantFail(tooling::applyAllReplacements(FinalCode, *Pass.second));
dlog("After {0}:\n{1}^{2}", Pass.first,
StringRef(FinalCode).take_front(FinalCursor),
StringRef(FinalCode).drop_front(FinalCursor));
#endif
}
return split(Final, OriginalCursor, FinalCursor);
}
unsigned
transformCursorPosition(unsigned Offset,
const std::vector<tooling::Replacement> &Replacements) {
unsigned OriginalOffset = Offset;
for (const auto &R : Replacements) {
if (R.getOffset() + R.getLength() <= OriginalOffset) {
// Replacement is before cursor.
Offset += R.getReplacementText().size();
Offset -= R.getLength();
} else if (R.getOffset() < OriginalOffset) {
// Replacement overlaps cursor.
// Preserve position within replacement text, as far as possible.
unsigned PositionWithinReplacement = Offset - R.getOffset();
if (PositionWithinReplacement > R.getReplacementText().size()) {
Offset += R.getReplacementText().size();
Offset -= PositionWithinReplacement;
}
} else {
// Replacement after cursor.
break; // Replacements are sorted, the rest are also after the cursor.
}
}
return Offset;
}
} // namespace clangd
} // namespace clang