Current File : //opt/alt/ruby32/share/ruby/syntax_suggest/code_frontier.rb
# frozen_string_literal: true
module SyntaxSuggest
# The main function of the frontier is to hold the edges of our search and to
# evaluate when we can stop searching.
# There are three main phases in the algorithm:
#
# 1. Sanitize/format input source
# 2. Search for invalid blocks
# 3. Format invalid blocks into something meaninful
#
# The Code frontier is a critical part of the second step
#
# ## Knowing where we've been
#
# Once a code block is generated it is added onto the frontier. Then it will be
# sorted by indentation and frontier can be filtered. Large blocks that fully enclose a
# smaller block will cause the smaller block to be evicted.
#
# CodeFrontier#<<(block) # Adds block to frontier
# CodeFrontier#pop # Removes block from frontier
#
# ## Knowing where we can go
#
# Internally the frontier keeps track of "unvisited" lines which are exposed via `next_indent_line`
# when called, this method returns, a line of code with the highest indentation.
#
# The returned line of code can be used to build a CodeBlock and then that code block
# is added back to the frontier. Then, the lines are removed from the
# "unvisited" so we don't double-create the same block.
#
# CodeFrontier#next_indent_line # Shows next line
# CodeFrontier#register_indent_block(block) # Removes lines from unvisited
#
# ## Knowing when to stop
#
# The frontier knows how to check the entire document for a syntax error. When blocks
# are added onto the frontier, they're removed from the document. When all code containing
# syntax errors has been added to the frontier, the document will be parsable without a
# syntax error and the search can stop.
#
# CodeFrontier#holds_all_syntax_errors? # Returns true when frontier holds all syntax errors
#
# ## Filtering false positives
#
# Once the search is completed, the frontier may have multiple blocks that do not contain
# the syntax error. To limit the result to the smallest subset of "invalid blocks" call:
#
# CodeFrontier#detect_invalid_blocks
#
class CodeFrontier
def initialize(code_lines:, unvisited: UnvisitedLines.new(code_lines: code_lines))
@code_lines = code_lines
@unvisited = unvisited
@queue = PriorityEngulfQueue.new
@check_next = true
end
def count
@queue.length
end
# Performance optimization
#
# Parsing with ripper is expensive
# If we know we don't have any blocks with invalid
# syntax, then we know we cannot have found
# the incorrect syntax yet.
#
# When an invalid block is added onto the frontier
# check document state
private def can_skip_check?
check_next = @check_next
@check_next = false
if check_next
false
else
true
end
end
# Returns true if the document is valid with all lines
# removed. By default it checks all blocks in present in
# the frontier array, but can be used for arbitrary arrays
# of codeblocks as well
def holds_all_syntax_errors?(block_array = @queue, can_cache: true)
return false if can_cache && can_skip_check?
without_lines = block_array.to_a.flat_map do |block|
block.lines
end
SyntaxSuggest.valid_without?(
without_lines: without_lines,
code_lines: @code_lines
)
end
# Returns a code block with the largest indentation possible
def pop
@queue.pop
end
def next_indent_line
@unvisited.peek
end
def expand?
return false if @queue.empty?
return true if @unvisited.empty?
frontier_indent = @queue.peek.current_indent
unvisited_indent = next_indent_line.indent
if ENV["SYNTAX_SUGGEST_DEBUG"]
puts "```"
puts @queue.peek.to_s
puts "```"
puts " @frontier indent: #{frontier_indent}"
puts " @unvisited indent: #{unvisited_indent}"
end
# Expand all blocks before moving to unvisited lines
frontier_indent >= unvisited_indent
end
# Keeps track of what lines have been added to blocks and which are not yet
# visited.
def register_indent_block(block)
@unvisited.visit_block(block)
self
end
# When one element fully encapsulates another we remove the smaller
# block from the frontier. This prevents double expansions and all-around
# weird behavior. However this guarantee is quite expensive to maintain
def register_engulf_block(block)
end
# Add a block to the frontier
#
# This method ensures the frontier always remains sorted (in indentation order)
# and that each code block's lines are removed from the indentation hash so we
# don't re-evaluate the same line multiple times.
def <<(block)
@unvisited.visit_block(block)
@queue.push(block)
@check_next = true if block.invalid?
self
end
# Example:
#
# combination([:a, :b, :c, :d])
# # => [[:a], [:b], [:c], [:d], [:a, :b], [:a, :c], [:a, :d], [:b, :c], [:b, :d], [:c, :d], [:a, :b, :c], [:a, :b, :d], [:a, :c, :d], [:b, :c, :d], [:a, :b, :c, :d]]
def self.combination(array)
guesses = []
1.upto(array.length).each do |size|
guesses.concat(array.combination(size).to_a)
end
guesses
end
# Given that we know our syntax error exists somewhere in our frontier, we want to find
# the smallest possible set of blocks that contain all the syntax errors
def detect_invalid_blocks
self.class.combination(@queue.to_a.select(&:invalid?)).detect do |block_array|
holds_all_syntax_errors?(block_array, can_cache: false)
end || []
end
end
end
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