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llvm-project/clang/lib/Format/BreakableToken.h

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//===--- BreakableToken.h - Format C++ code ---------------------*- 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Declares BreakableToken, BreakableStringLiteral, BreakableComment,
/// BreakableBlockComment and BreakableLineCommentSection classes, that contain
/// token type-specific logic to break long lines in tokens and reflow content
/// between tokens.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_LIB_FORMAT_BREAKABLETOKEN_H
#define LLVM_CLANG_LIB_FORMAT_BREAKABLETOKEN_H
#include "Encoding.h"
#include "TokenAnnotator.h"
#include "WhitespaceManager.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/Regex.h"
#include <utility>
namespace clang {
namespace format {
/// Checks if \p Token switches formatting, like /* clang-format off */.
/// \p Token must be a comment.
bool switchesFormatting(const FormatToken &Token);
struct FormatStyle;
/// Base class for tokens / ranges of tokens that can allow breaking
/// within the tokens - for example, to avoid whitespace beyond the column
/// limit, or to reflow text.
///
/// Generally, a breakable token consists of logical lines, addressed by a line
/// index. For example, in a sequence of line comments, each line comment is its
/// own logical line; similarly, for a block comment, each line in the block
/// comment is on its own logical line.
///
/// There are two methods to compute the layout of the token:
/// - getRangeLength measures the number of columns needed for a range of text
/// within a logical line, and
/// - getContentStartColumn returns the start column at which we want the
/// content of a logical line to start (potentially after introducing a line
/// break).
///
/// The mechanism to adapt the layout of the breakable token is organised
/// around the concept of a \c Split, which is a whitespace range that signifies
/// a position of the content of a token where a reformatting might be done.
///
/// Operating with splits is divided into two operations:
/// - getSplit, for finding a split starting at a position,
/// - insertBreak, for executing the split using a whitespace manager.
///
/// There is a pair of operations that are used to compress a long whitespace
/// range with a single space if that will bring the line length under the
/// column limit:
/// - getLineLengthAfterCompression, for calculating the size in columns of the
/// line after a whitespace range has been compressed, and
/// - compressWhitespace, for executing the whitespace compression using a
/// whitespace manager; note that the compressed whitespace may be in the
/// middle of the original line and of the reformatted line.
///
/// For tokens where the whitespace before each line needs to be also
/// reformatted, for example for tokens supporting reflow, there are analogous
/// operations that might be executed before the main line breaking occurs:
/// - getReflowSplit, for finding a split such that the content preceding it
/// needs to be specially reflown,
/// - reflow, for executing the split using a whitespace manager,
/// - introducesBreakBefore, for checking if reformatting the beginning
/// of the content introduces a line break before it,
/// - adaptStartOfLine, for executing the reflow using a whitespace
/// manager.
///
/// For tokens that require the whitespace after the last line to be
/// reformatted, for example in multiline jsdoc comments that require the
/// trailing '*/' to be on a line of itself, there are analogous operations
/// that might be executed after the last line has been reformatted:
/// - getSplitAfterLastLine, for finding a split after the last line that needs
/// to be reflown,
/// - replaceWhitespaceAfterLastLine, for executing the reflow using a
/// whitespace manager.
///
class BreakableToken {
public:
/// Contains starting character index and length of split.
typedef std::pair<StringRef::size_type, unsigned> Split;
virtual ~BreakableToken() {}
/// Returns the number of lines in this token in the original code.
virtual unsigned getLineCount() const = 0;
/// Returns the number of columns required to format the text in the
/// byte range [\p Offset, \p Offset \c + \p Length).
///
/// \p Offset is the byte offset from the start of the content of the line
/// at \p LineIndex.
///
/// \p StartColumn is the column at which the text starts in the formatted
/// file, needed to compute tab stops correctly.
virtual unsigned getRangeLength(unsigned LineIndex, unsigned Offset,
StringRef::size_type Length,
unsigned StartColumn) const = 0;
/// Returns the number of columns required to format the text following
/// the byte \p Offset in the line \p LineIndex, including potentially
/// unbreakable sequences of tokens following after the end of the token.
///
/// \p Offset is the byte offset from the start of the content of the line
/// at \p LineIndex.
///
/// \p StartColumn is the column at which the text starts in the formatted
/// file, needed to compute tab stops correctly.
///
/// For breakable tokens that never use extra space at the end of a line, this
/// is equivalent to getRangeLength with a Length of StringRef::npos.
virtual unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
unsigned StartColumn) const {
return getRangeLength(LineIndex, Offset, StringRef::npos, StartColumn);
}
/// Returns the column at which content in line \p LineIndex starts,
/// assuming no reflow.
///
/// If \p Break is true, returns the column at which the line should start
/// after the line break.
/// If \p Break is false, returns the column at which the line itself will
/// start.
virtual unsigned getContentStartColumn(unsigned LineIndex,
bool Break) const = 0;
/// Returns additional content indent required for the second line after the
/// content at line \p LineIndex is broken.
///
// (Next lines do not start with `///` since otherwise -Wdocumentation picks
// up the example annotations and generates warnings for them)
// For example, Javadoc @param annotations require and indent of 4 spaces and
// in this example getContentIndex(1) returns 4.
// /**
// * @param loooooooooooooong line
// * continuation
// */
virtual unsigned getContentIndent(unsigned LineIndex) const { return 0; }
/// Returns a range (offset, length) at which to break the line at
/// \p LineIndex, if previously broken at \p TailOffset. If possible, do not
/// violate \p ColumnLimit, assuming the text starting at \p TailOffset in
/// the token is formatted starting at ContentStartColumn in the reformatted
/// file.
virtual Split getSplit(unsigned LineIndex, unsigned TailOffset,
unsigned ColumnLimit, unsigned ContentStartColumn,
llvm::Regex &CommentPragmasRegex) const = 0;
/// Emits the previously retrieved \p Split via \p Whitespaces.
virtual void insertBreak(unsigned LineIndex, unsigned TailOffset, Split Split,
unsigned ContentIndent,
WhitespaceManager &Whitespaces) const = 0;
/// Returns the number of columns needed to format
/// \p RemainingTokenColumns, assuming that Split is within the range measured
/// by \p RemainingTokenColumns, and that the whitespace in Split is reduced
/// to a single space.
unsigned getLengthAfterCompression(unsigned RemainingTokenColumns,
Split Split) const;
/// Replaces the whitespace range described by \p Split with a single
/// space.
virtual void compressWhitespace(unsigned LineIndex, unsigned TailOffset,
Split Split,
WhitespaceManager &Whitespaces) const = 0;
/// Returns whether the token supports reflowing text.
virtual bool supportsReflow() const { return false; }
/// Returns a whitespace range (offset, length) of the content at \p
/// LineIndex such that the content of that line is reflown to the end of the
/// previous one.
///
/// Returning (StringRef::npos, 0) indicates reflowing is not possible.
///
/// The range will include any whitespace preceding the specified line's
/// content.
///
/// If the split is not contained within one token, for example when reflowing
/// line comments, returns (0, <length>).
virtual Split getReflowSplit(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const {
return Split(StringRef::npos, 0);
}
/// Reflows the current line into the end of the previous one.
virtual void reflow(unsigned LineIndex,
WhitespaceManager &Whitespaces) const {}
/// Returns whether there will be a line break at the start of the
/// token.
virtual bool introducesBreakBeforeToken() const { return false; }
/// Replaces the whitespace between \p LineIndex-1 and \p LineIndex.
virtual void adaptStartOfLine(unsigned LineIndex,
WhitespaceManager &Whitespaces) const {}
/// Returns a whitespace range (offset, length) of the content at
/// the last line that needs to be reformatted after the last line has been
/// reformatted.
///
/// A result having offset == StringRef::npos means that no reformat is
/// necessary.
virtual Split getSplitAfterLastLine(unsigned TailOffset) const {
return Split(StringRef::npos, 0);
}
/// Replaces the whitespace from \p SplitAfterLastLine on the last line
/// after the last line has been formatted by performing a reformatting.
void replaceWhitespaceAfterLastLine(unsigned TailOffset,
Split SplitAfterLastLine,
WhitespaceManager &Whitespaces) const {
insertBreak(getLineCount() - 1, TailOffset, SplitAfterLastLine,
/*ContentIndent=*/0, Whitespaces);
}
/// Updates the next token of \p State to the next token after this
/// one. This can be used when this token manages a set of underlying tokens
/// as a unit and is responsible for the formatting of the them.
virtual void updateNextToken(LineState &State) const {}
protected:
BreakableToken(const FormatToken &Tok, bool InPPDirective,
encoding::Encoding Encoding, const FormatStyle &Style)
: Tok(Tok), InPPDirective(InPPDirective), Encoding(Encoding),
Style(Style) {}
const FormatToken &Tok;
const bool InPPDirective;
const encoding::Encoding Encoding;
const FormatStyle &Style;
};
class BreakableStringLiteral : public BreakableToken {
public:
/// Creates a breakable token for a single line string literal.
///
/// \p StartColumn specifies the column in which the token will start
/// after formatting.
BreakableStringLiteral(const FormatToken &Tok, unsigned StartColumn,
StringRef Prefix, StringRef Postfix,
unsigned UnbreakableTailLength, bool InPPDirective,
encoding::Encoding Encoding, const FormatStyle &Style);
Split getSplit(unsigned LineIndex, unsigned TailOffset, unsigned ColumnLimit,
unsigned ContentStartColumn,
llvm::Regex &CommentPragmasRegex) const override;
void insertBreak(unsigned LineIndex, unsigned TailOffset, Split Split,
unsigned ContentIndent,
WhitespaceManager &Whitespaces) const override;
void compressWhitespace(unsigned LineIndex, unsigned TailOffset, Split Split,
WhitespaceManager &Whitespaces) const override {}
unsigned getLineCount() const override;
unsigned getRangeLength(unsigned LineIndex, unsigned Offset,
StringRef::size_type Length,
unsigned StartColumn) const override;
unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
unsigned StartColumn) const override;
unsigned getContentStartColumn(unsigned LineIndex, bool Break) const override;
protected:
// The column in which the token starts.
unsigned StartColumn;
// The prefix a line needs after a break in the token.
StringRef Prefix;
// The postfix a line needs before introducing a break.
StringRef Postfix;
// The token text excluding the prefix and postfix.
StringRef Line;
// Length of the sequence of tokens after this string literal that cannot
// contain line breaks.
unsigned UnbreakableTailLength;
};
class BreakableComment : public BreakableToken {
protected:
/// Creates a breakable token for a comment.
///
/// \p StartColumn specifies the column in which the comment will start after
/// formatting.
BreakableComment(const FormatToken &Token, unsigned StartColumn,
bool InPPDirective, encoding::Encoding Encoding,
const FormatStyle &Style);
public:
bool supportsReflow() const override { return true; }
unsigned getLineCount() const override;
Split getSplit(unsigned LineIndex, unsigned TailOffset, unsigned ColumnLimit,
unsigned ContentStartColumn,
llvm::Regex &CommentPragmasRegex) const override;
void compressWhitespace(unsigned LineIndex, unsigned TailOffset, Split Split,
WhitespaceManager &Whitespaces) const override;
protected:
// Returns the token containing the line at LineIndex.
const FormatToken &tokenAt(unsigned LineIndex) const;
// Checks if the content of line LineIndex may be reflown with the previous
// line.
virtual bool mayReflow(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const = 0;
// Contains the original text of the lines of the block comment.
//
// In case of a block comments, excludes the leading /* in the first line and
// trailing */ in the last line. In case of line comments, excludes the
// leading // and spaces.
SmallVector<StringRef, 16> Lines;
// Contains the text of the lines excluding all leading and trailing
// whitespace between the lines. Note that the decoration (if present) is also
// not considered part of the text.
SmallVector<StringRef, 16> Content;
// Tokens[i] contains a reference to the token containing Lines[i] if the
// whitespace range before that token is managed by this block.
// Otherwise, Tokens[i] is a null pointer.
SmallVector<FormatToken *, 16> Tokens;
// ContentColumn[i] is the target column at which Content[i] should be.
// Note that this excludes a leading "* " or "*" in case of block comments
// where all lines have a "*" prefix, or the leading "// " or "//" in case of
// line comments.
//
// In block comments, the first line's target column is always positive. The
// remaining lines' target columns are relative to the first line to allow
// correct indentation of comments in \c WhitespaceManager. Thus they can be
// negative as well (in case the first line needs to be unindented more than
// there's actual whitespace in another line).
SmallVector<int, 16> ContentColumn;
// The intended start column of the first line of text from this section.
unsigned StartColumn;
// The prefix to use in front a line that has been reflown up.
// For example, when reflowing the second line after the first here:
// // comment 1
// // comment 2
// we expect:
// // comment 1 comment 2
// and not:
// // comment 1comment 2
StringRef ReflowPrefix = " ";
};
class BreakableBlockComment : public BreakableComment {
public:
BreakableBlockComment(const FormatToken &Token, unsigned StartColumn,
unsigned OriginalStartColumn, bool FirstInLine,
bool InPPDirective, encoding::Encoding Encoding,
const FormatStyle &Style);
unsigned getRangeLength(unsigned LineIndex, unsigned Offset,
StringRef::size_type Length,
unsigned StartColumn) const override;
unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
unsigned StartColumn) const override;
unsigned getContentStartColumn(unsigned LineIndex, bool Break) const override;
unsigned getContentIndent(unsigned LineIndex) const override;
void insertBreak(unsigned LineIndex, unsigned TailOffset, Split Split,
unsigned ContentIndent,
WhitespaceManager &Whitespaces) const override;
Split getReflowSplit(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const override;
void reflow(unsigned LineIndex,
WhitespaceManager &Whitespaces) const override;
bool introducesBreakBeforeToken() const override;
void adaptStartOfLine(unsigned LineIndex,
WhitespaceManager &Whitespaces) const override;
Split getSplitAfterLastLine(unsigned TailOffset) const override;
bool mayReflow(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const override;
// Contains Javadoc annotations that require additional indent when continued
// on multiple lines.
static const llvm::StringSet<> ContentIndentingJavadocAnnotations;
private:
// Rearranges the whitespace between Lines[LineIndex-1] and Lines[LineIndex].
//
// Updates Content[LineIndex-1] and Content[LineIndex] by stripping off
// leading and trailing whitespace.
//
// Sets ContentColumn to the intended column in which the text at
// Lines[LineIndex] starts (note that the decoration, if present, is not
// considered part of the text).
void adjustWhitespace(unsigned LineIndex, int IndentDelta);
// The column at which the text of a broken line should start.
// Note that an optional decoration would go before that column.
// IndentAtLineBreak is a uniform position for all lines in a block comment,
// regardless of their relative position.
// FIXME: Revisit the decision to do this; the main reason was to support
// patterns like
// /**************//**
// * Comment
// We could also support such patterns by special casing the first line
// instead.
unsigned IndentAtLineBreak;
// This is to distinguish between the case when the last line was empty and
// the case when it started with a decoration ("*" or "* ").
bool LastLineNeedsDecoration;
// Either "* " if all lines begin with a "*", or empty.
StringRef Decoration;
// If this block comment has decorations, this is the column of the start of
// the decorations.
unsigned DecorationColumn;
// If true, make sure that the opening '/**' and the closing '*/' ends on a
// line of itself. Styles like jsdoc require this for multiline comments.
bool DelimitersOnNewline;
// Length of the sequence of tokens after this string literal that cannot
// contain line breaks.
unsigned UnbreakableTailLength;
};
class BreakableLineCommentSection : public BreakableComment {
public:
BreakableLineCommentSection(const FormatToken &Token, unsigned StartColumn,
unsigned OriginalStartColumn, bool FirstInLine,
bool InPPDirective, encoding::Encoding Encoding,
const FormatStyle &Style);
unsigned getRangeLength(unsigned LineIndex, unsigned Offset,
StringRef::size_type Length,
unsigned StartColumn) const override;
unsigned getContentStartColumn(unsigned LineIndex, bool Break) const override;
void insertBreak(unsigned LineIndex, unsigned TailOffset, Split Split,
unsigned ContentIndent,
WhitespaceManager &Whitespaces) const override;
Split getReflowSplit(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const override;
void reflow(unsigned LineIndex,
WhitespaceManager &Whitespaces) const override;
void adaptStartOfLine(unsigned LineIndex,
WhitespaceManager &Whitespaces) const override;
void updateNextToken(LineState &State) const override;
bool mayReflow(unsigned LineIndex,
llvm::Regex &CommentPragmasRegex) const override;
private:
// OriginalPrefix[i] contains the original prefix of line i, including
// trailing whitespace before the start of the content. The indentation
// preceding the prefix is not included.
// For example, if the line is:
// // content
// then the original prefix is "// ".
SmallVector<StringRef, 16> OriginalPrefix;
// Prefix[i] contains the intended leading "//" with trailing spaces to
// account for the indentation of content within the comment at line i after
// formatting. It can be different than the original prefix when the original
// line starts like this:
// //content
// Then the original prefix is "//", but the prefix is "// ".
SmallVector<StringRef, 16> Prefix;
SmallVector<unsigned, 16> OriginalContentColumn;
/// The token to which the last line of this breakable token belongs
/// to; nullptr if that token is the initial token.
///
/// The distinction is because if the token of the last line of this breakable
/// token is distinct from the initial token, this breakable token owns the
/// whitespace before the token of the last line, and the whitespace manager
/// must be able to modify it.
FormatToken *LastLineTok = nullptr;
};
} // namespace format
} // namespace clang
#endif
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