class Prism::Source

This represents a source of Ruby code that has been parsed. It is used in conjunction with locations to allow them to resolve line numbers and source ranges.

Attributes

offsets[R]

The list of newline byte offsets in the source code.

source[R]

The source code that this source object represents.

start_line[R]

The line number where this source starts.

Public Class Methods

for(source, start_line = 1, offsets = []) click to toggle source

Create a new source object with the given source code. This method should be used instead of ‘new` and it will return either a `Source` or a specialized and more performant `ASCIISource` if no multibyte characters are present in the source code.

# File prism/parse_result.rb, line 12
def self.for(source, start_line = 1, offsets = [])
  if source.ascii_only?
    ASCIISource.new(source, start_line, offsets)
  elsif source.encoding == Encoding::BINARY
    source.force_encoding(Encoding::UTF_8)

    if source.valid_encoding?
      new(source, start_line, offsets)
    else
      # This is an extremely niche use case where the file is marked as
      # binary, contains multi-byte characters, and those characters are not
      # valid UTF-8. In this case we'll mark it as binary and fall back to
      # treating everything as a single-byte character. This _may_ cause
      # problems when asking for code units, but it appears to be the
      # cleanest solution at the moment.
      source.force_encoding(Encoding::BINARY)
      ASCIISource.new(source, start_line, offsets)
    end
  else
    new(source, start_line, offsets)
  end
end

new(source, start_line = 1, offsets = []) click to toggle source

Create a new source object with the given source code.

# File prism/parse_result.rb, line 45
def initialize(source, start_line = 1, offsets = [])
  @source = source
  @start_line = start_line # set after parsing is done
  @offsets = offsets # set after parsing is done
end

Public Instance Methods

character_column(byte_offset) click to toggle source

Return the column number in characters for the given byte offset.

# File prism/parse_result.rb, line 97
def character_column(byte_offset)
  character_offset(byte_offset) - character_offset(line_start(byte_offset))
end

character_offset(byte_offset) click to toggle source

Return the character offset for the given byte offset.

# File prism/parse_result.rb, line 92
def character_offset(byte_offset)
  (source.byteslice(0, byte_offset) or raise).length
end

code_units_cache(encoding) click to toggle source

Generate a cache that targets a specific encoding for calculating code unit offsets.

# File prism/parse_result.rb, line 125
def code_units_cache(encoding)
  CodeUnitsCache.new(source, encoding)
end

code_units_column(byte_offset, encoding) click to toggle source

Returns the column number in code units for the given encoding for the given byte offset.

# File prism/parse_result.rb, line 131
def code_units_column(byte_offset, encoding)
  code_units_offset(byte_offset, encoding) - code_units_offset(line_start(byte_offset), encoding)
end

code_units_offset(byte_offset, encoding) click to toggle source

Returns the offset from the start of the file for the given byte offset counting in code units for the given encoding.

This method is tested with UTF-8, UTF-16, and UTF-32. If there is the concept of code units that differs from the number of characters in other encodings, it is not captured here.

We purposefully replace invalid and undefined characters with replacement characters in this conversion. This happens for two reasons. First, it’s possible that the given byte offset will not occur on a character boundary. Second, it’s possible that the source code will contain a character that has no equivalent in the given encoding.

# File prism/parse_result.rb, line 113
def code_units_offset(byte_offset, encoding)
  byteslice = (source.byteslice(0, byte_offset) or raise).encode(encoding, invalid: :replace, undef: :replace)

  if encoding == Encoding::UTF_16LE || encoding == Encoding::UTF_16BE
    byteslice.bytesize / 2
  else
    byteslice.length
  end
end

column(byte_offset) click to toggle source

Return the column number for the given byte offset.

# File prism/parse_result.rb, line 87
def column(byte_offset)
  byte_offset - line_start(byte_offset)
end

encoding() click to toggle source

Returns the encoding of the source code, which is set by parameters to the parser or by the encoding magic comment.

# File prism/parse_result.rb, line 53
def encoding
  source.encoding
end

line(byte_offset) click to toggle source

Binary search through the offsets to find the line number for the given byte offset.

# File prism/parse_result.rb, line 70
def line(byte_offset)
  start_line + find_line(byte_offset)
end

line_end(byte_offset) click to toggle source

Returns the byte offset of the end of the line corresponding to the given byte offset.

# File prism/parse_result.rb, line 82
def line_end(byte_offset)
  offsets[find_line(byte_offset) + 1] || source.bytesize
end

line_start(byte_offset) click to toggle source

Return the byte offset of the start of the line corresponding to the given byte offset.

# File prism/parse_result.rb, line 76
def line_start(byte_offset)
  offsets[find_line(byte_offset)]
end

lines() click to toggle source

Returns the lines of the source code as an array of strings.

# File prism/parse_result.rb, line 58
def lines
  source.lines
end

slice(byte_offset, length) click to toggle source

Perform a byteslice on the source code using the given byte offset and byte length.

# File prism/parse_result.rb, line 64
def slice(byte_offset, length)
  source.byteslice(byte_offset, length) or raise
end

Private Instance Methods

find_line(byte_offset) click to toggle source

Binary search through the offsets to find the line number for the given byte offset.

# File prism/parse_result.rb, line 139
def find_line(byte_offset)
  left = 0
  right = offsets.length - 1

  while left <= right
    mid = left + (right - left) / 2
    return mid if (offset = offsets[mid]) == byte_offset

    if offset < byte_offset
      left = mid + 1
    else
      right = mid - 1
    end
  end

  left - 1
end