class SyntaxSuggest::CaptureCodeContext
Turns a “invalid block(s)” into useful context
There are three main phases in the algorithm:
-
Sanitize/format input source
-
Search for invalid blocks
-
Format invalid blocks into something meaninful
This class handles the third part.
The algorithm is very good at capturing all of a syntax error in a single block in number 2, however the results can contain ambiguities. Humans are good at pattern matching and filtering and can mentally remove extraneous data, but they can’t add extra data that’s not present.
In the case of known ambiguious cases, this class adds context back to the ambiguitiy so the programmer has full information.
Beyond handling these ambiguities, it also captures surrounding code context information:
puts block.to_s # => "def bark"
context = CaptureCodeContext.new(
blocks: block,
code_lines: code_lines
)
lines = context.call.map(&:original)
puts lines.join
# =>
class Dog
def bark
end
Attributes
Public Class Methods
# File syntax_suggest/capture_code_context.rb, line 43 def initialize(blocks:, code_lines:) @blocks = Array(blocks) @code_lines = code_lines @visible_lines = @blocks.map(&:visible_lines).flatten @lines_to_output = @visible_lines.dup end
Public Instance Methods
# File syntax_suggest/capture_code_context.rb, line 50 def call @blocks.each do |block| capture_first_kw_end_same_indent(block) capture_last_end_same_indent(block) capture_before_after_kws(block) capture_falling_indent(block) end @lines_to_output.select!(&:not_empty?) @lines_to_output.uniq! @lines_to_output.sort! @lines_to_output end
Shows surrounding kw/end pairs
The purpose of showing these extra pairs is due to cases of ambiguity when only one visible line is matched.
For example:
1 class Dog 2 def bark 4 def eat 5 end 6 end
In this case either line 2 could be missing an ‘end` or line 4 was an extra line added by mistake (it happens).
When we detect the above problem it shows the issue as only being on line 2
2 def bark
Showing “neighbor” keyword pairs gives extra context:
2 def bark 4 def eat 5 end
# File syntax_suggest/capture_code_context.rb, line 116 def capture_before_after_kws(block) return unless block.visible_lines.count == 1 around_lines = AroundBlockScan.new(code_lines: @code_lines, block: block) .start_at_next_line .capture_neighbor_context around_lines -= block.lines @lines_to_output.concat(around_lines) end
Shows the context around code provided by “falling” indentation
Converts:
it "foo" do
into:
class OH
def hello
it "foo" do
end
end
# File syntax_suggest/capture_code_context.rb, line 80 def capture_falling_indent(block) AroundBlockScan.new( block: block, code_lines: @code_lines ).on_falling_indent do |line| @lines_to_output << line end end
The logical inverse of ‘capture_last_end_same_indent`
When there is an invalid block with an ‘end` missing a keyword right after another `end`, it is unclear where which end is missing the keyword.
Take this example:
class Dog # 1
puts "woof" # 2
end # 3
end # 4
the problem line will be identified as:
> end # 4
This happens because lines 1, 2, and 3 are technically valid code and are expanded first, deemed valid, and hidden. We need to un-hide the matching keyword on line 1. Also work backwards and if there’s a mis-matched end, show it too
# File syntax_suggest/capture_code_context.rb, line 209 def capture_first_kw_end_same_indent(block) return if block.visible_lines.length != 1 return unless block.visible_lines.first.is_end? visible_line = block.visible_lines.first lines = @code_lines[block.lines.first.index..visible_line.index] matching_kw = lines.reverse.detect { |line| line.indent == block.current_indent && line.is_kw? } return unless matching_kw @lines_to_output << matching_kw kw_count = 0 end_count = 0 orphan_end = @code_lines[matching_kw.index..visible_line.index].detect do |line| kw_count += 1 if line.is_kw? end_count += 1 if line.is_end? end_count >= kw_count end return unless orphan_end @lines_to_output << orphan_end end
When there is an invalid block with a keyword missing an end right before another end, it is unclear where which keyword is missing the end
Take this example:
class Dog # 1
def bark # 2
puts "woof" # 3
end # 4
However due to github.com/ruby/syntax_suggest/issues/32 the problem line will be identified as:
> class Dog # 1
Because lines 2, 3, and 4 are technically valid code and are expanded first, deemed valid, and hidden. We need to un-hide the matching end line 4. Also work backwards and if there’s a mis-matched keyword, show it too
# File syntax_suggest/capture_code_context.rb, line 149 def capture_last_end_same_indent(block) return if block.visible_lines.length != 1 return unless block.visible_lines.first.is_kw? visible_line = block.visible_lines.first lines = @code_lines[visible_line.index..block.lines.last.index] # Find first end with same indent # (this would return line 4) # # end # 4 matching_end = lines.detect { |line| line.indent == block.current_indent && line.is_end? } return unless matching_end @lines_to_output << matching_end # Work backwards from the end to # see if there are mis-matched # keyword/end pairs # # Return the first mis-matched keyword # this would find line 2 # # def bark # 2 # puts "woof" # 3 # end # 4 end_count = 0 kw_count = 0 kw_line = @code_lines[visible_line.index..matching_end.index].reverse.detect do |line| end_count += 1 if line.is_end? kw_count += 1 if line.is_kw? !kw_count.zero? && kw_count >= end_count end return unless kw_line @lines_to_output << kw_line end