class Prism::Node

This represents a node in the tree. It is the parent class of all of the various node types.

Attributes

flags[R]

An bitset of flags for this node. There are certain flags that are common for all nodes, and then some nodes have specific flags.

node_id[R]

A unique identifier for this node. This is used in a very specific use case where you want to keep around a reference to a node without having to keep around the syntax tree in memory. This unique identifier will be consistent across multiple parses of the same source code.

source[R]

A pointer to the source that this node was created from.

Public Class Methods

fields() click to toggle source

Returns a list of the fields that exist for this node class. Fields describe the structure of the node. This kind of reflection is useful for things like recursively visiting each node and field in the tree.

# File lib/prism/node.rb, line 153
def self.fields
  # This method should only be called on subclasses of Node, not Node
  # itself.
  raise NoMethodError, "undefined method `fields' for #{inspect}" if self == Node

  Reflection.fields_for(self)
end

Public Instance Methods

breadth_first_search() { |node| ... } click to toggle source

Returns the first node that matches the given block when visited in a depth-first search. This is useful for finding a node that matches a particular condition.

node.breadth_first_search { |node| node.node_id == node_id }

# File lib/prism/node.rb, line 139
def breadth_first_search(&block)
  queue = [self] #: Array[Prism::node]

  while (node = queue.shift)
    return node if yield node
    queue.concat(node.compact_child_nodes)
  end

  nil
end

end_offset() click to toggle source

The end offset of the node in the source. This method is effectively a delegate method to the location object.

# File lib/prism/node.rb, line 40
def end_offset
  location = @location
  location.is_a?(Location) ? location.end_offset : ((location >> 32) + (location & 0xFFFFFFFF))
end

location() click to toggle source

A Location instance that represents the location of this node in the source.

# File lib/prism/node.rb, line 25
def location
  location = @location
  return location if location.is_a?(Location)
  @location = Location.new(source, location >> 32, location & 0xFFFFFFFF)
end

newline?() click to toggle source

Returns true if the node has the newline flag set.

# File lib/prism/node.rb, line 72
def newline?
  flags.anybits?(NodeFlags::NEWLINE)
end

pretty_print(q) click to toggle source

Similar to inspect, but respects the current level of indentation given by the pretty print object.

# File lib/prism/node.rb, line 83
def pretty_print(q)
  q.seplist(inspect.chomp.each_line, -> { q.breakable }) do |line|
    q.text(line.chomp)
  end
  q.current_group.break
end

script_lines()

An alias for source_lines, used to mimic the API from RubyVM::AbstractSyntaxTree to make it easier to migrate.

Alias for: source_lines

slice() click to toggle source

Slice the location of the node from the source.

# File lib/prism/node.rb, line 55
def slice
  location.slice
end

slice_lines() click to toggle source

Slice the location of the node from the source, starting at the beginning of the line that the location starts on, ending at the end of the line that the location ends on.

# File lib/prism/node.rb, line 62
def slice_lines
  location.slice_lines
end

source_lines() click to toggle source

Returns all of the lines of the source code associated with this node.

# File lib/prism/node.rb, line 46
def source_lines
  location.source_lines
end

Also aliased as: script_lines

start_offset() click to toggle source

The start offset of the node in the source. This method is effectively a delegate method to the location object.

# File lib/prism/node.rb, line 33
def start_offset
  location = @location
  location.is_a?(Location) ? location.start_offset : location >> 32
end

static_literal?() click to toggle source

Returns true if the node has the static literal flag set.

# File lib/prism/node.rb, line 77
def static_literal?
  flags.anybits?(NodeFlags::STATIC_LITERAL)
end

to_dot() click to toggle source

Convert this node into a graphviz dot graph string.

# File lib/prism/node.rb, line 91
def to_dot
  # @type self: node
  DotVisitor.new.tap { |visitor| accept(visitor) }.to_dot
end

tunnel(line, column) click to toggle source

Returns a list of nodes that are descendants of this node that contain the given line and column. This is useful for locating a node that is selected based on the line and column of the source code.

Important to note is that the column given to this method should be in bytes, as opposed to characters or code units.

# File lib/prism/node.rb, line 102
def tunnel(line, column)
  queue = [self] #: Array[Prism::node]
  result = []

  while (node = queue.shift)
    result << node

    node.compact_child_nodes.each do |child_node|
      child_location = child_node.location

      start_line = child_location.start_line
      end_line = child_location.end_line

      if start_line == end_line
        if line == start_line && column >= child_location.start_column && column < child_location.end_column
          queue << child_node
          break
        end
      elsif (line == start_line && column >= child_location.start_column) || (line == end_line && column < child_location.end_column)
        queue << child_node
        break
      elsif line > start_line && line < end_line
        queue << child_node
        break
      end
    end
  end

  result
end

Node interface

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Public Class Methods

type() click to toggle source

Similar to type, this method returns a symbol that you can use for splitting on the type of the node without having to do a long === chain. Note that like type, it will still be slower than using == for a single class, but should be faster in a case statement or an array comparison.

# File lib/prism/node.rb, line 218
def self.type
  raise NoMethodError, "undefined method `type' for #{inspect}"
end

Public Instance Methods

accept(visitor) click to toggle source

Accepts a visitor and calls back into the specialized visit function.

# File lib/prism/node.rb, line 169
def accept(visitor)
  raise NoMethodError, "undefined method `accept' for #{inspect}"
end

child_nodes() click to toggle source

Returns an array of child nodes, including ‘nil`s in the place of optional nodes that were not present.

# File lib/prism/node.rb, line 175
def child_nodes
  raise NoMethodError, "undefined method `child_nodes' for #{inspect}"
end

Also aliased as: deconstruct

comment_targets() click to toggle source

Returns an array of child nodes and locations that could potentially have comments attached to them.

# File lib/prism/node.rb, line 189
def comment_targets
  raise NoMethodError, "undefined method `comment_targets' for #{inspect}"
end

compact_child_nodes() click to toggle source

Returns an array of child nodes, excluding any ‘nil`s in the place of optional nodes that were not present.

# File lib/prism/node.rb, line 183
def compact_child_nodes
  raise NoMethodError, "undefined method `compact_child_nodes' for #{inspect}"
end

deconstruct()

Alias for: child_nodes

inspect() click to toggle source

Returns a string representation of the node.

# File lib/prism/node.rb, line 194
def inspect
  raise NoMethodError, "undefined method `inspect' for #{inspect}"
end

type() click to toggle source

Sometimes you want to check an instance of a node against a list of classes to see what kind of behavior to perform. Usually this is done by calling ‘[cls1, cls2].include?(node.class)` or putting the node into a case statement and doing `case node; when cls1; when cls2; end`. Both of these approaches are relatively slow because of the constant lookups, method calls, and/or array allocations.

Instead, you can call type, which will return to you a symbol that you can use for comparison. This is faster than the other approaches because it uses a single integer comparison, but also because if you’re on CRuby you can take advantage of the fact that case statements with all symbol keys will use a jump table.

# File lib/prism/node.rb, line 210
def type
  raise NoMethodError, "undefined method `type' for #{inspect}"
end