class Prism::ParseResult::Comments
When we’ve parsed the source, we have both the syntax tree and the list of comments that we found in the source. This class is responsible for walking the tree and finding the nearest location to attach each comment.
It does this by first finding the nearest locations to each comment. Locations can either come from nodes directly or from location fields on nodes. For example, a ‘ClassNode` has an overall location encompassing the entire class, but it also has a location for the `class` keyword.
Once the nearest locations are found, it determines which one to attach to. If it’s a trailing comment (a comment on the same line as other source code), it will favor attaching to the nearest location that occurs before the comment. Otherwise it will favor attaching to the nearest location that is after the comment.
Attributes
The parse result that we are attaching comments to.
Public Class Methods
Create a new Comments
object that will attach comments to the given parse result.
# File prism/parse_result/comments.rb, line 78 def initialize(parse_result) @parse_result = parse_result end
Public Instance Methods
Attach the comments to their respective locations in the tree by mutating the parse result.
# File prism/parse_result/comments.rb, line 84 def attach! parse_result.comments.each do |comment| preceding, enclosing, following = nearest_targets(parse_result.value, comment) target = if comment.trailing? preceding || following || enclosing || NodeTarget.new(parse_result.value) else # If a comment exists on its own line, prefer a leading comment. following || preceding || enclosing || NodeTarget.new(parse_result.value) end target << comment end end
Private Instance Methods
Responsible for finding the nearest targets to the given comment within the context of the given encapsulating node.
# File prism/parse_result/comments.rb, line 103 def nearest_targets(node, comment) comment_start = comment.location.start_offset comment_end = comment.location.end_offset targets = [] node.comment_targets.map do |value| case value when StatementsNode targets.concat(value.body.map { |node| NodeTarget.new(node) }) when Node targets << NodeTarget.new(value) when Location targets << LocationTarget.new(value) end end targets.sort_by!(&:start_offset) preceding = nil following = nil left = 0 right = targets.length # This is a custom binary search that finds the nearest nodes to the # given comment. When it finds a node that completely encapsulates the # comment, it recurses downward into the tree. while left < right middle = (left + right) / 2 target = targets[middle] target_start = target.start_offset target_end = target.end_offset if target.encloses?(comment) # The comment is completely contained by this target. Abandon the # binary search at this level. return nearest_targets(target.node, comment) end if target_end <= comment_start # This target falls completely before the comment. Because we will # never consider this target or any targets before it again, this # target must be the closest preceding target we have encountered so # far. preceding = target left = middle + 1 next end if comment_end <= target_start # This target falls completely after the comment. Because we will # never consider this target or any targets after it again, this # target must be the closest following target we have encountered so # far. following = target right = middle next end # This should only happen if there is a bug in this parser. raise "Comment location overlaps with a target location" end [preceding, NodeTarget.new(node), following] end