class SyntaxSuggest::ExplainSyntax

Explains syntax errors based on their source

example:

source = "def foo; puts 'lol'" # Note missing end
explain ExplainSyntax.new(
  code_lines: CodeLine.from_source(source)
).call
explain.errors.first
# => "Unmatched keyword, missing `end' ?"

When the error cannot be determined by lexical counting then ripper is run against the input and the raw ripper errors returned.

Example:

source = "1 * " # Note missing a second number
explain ExplainSyntax.new(
  code_lines: CodeLine.from_source(source)
).call
explain.errors.first
# => "syntax error, unexpected end-of-input"

Constants

INVERSE

Public Class Methods

new(code_lines:) click to toggle source

# File lib/syntax_suggest/explain_syntax.rb, line 40
def initialize(code_lines:)
  @code_lines = code_lines
  @left_right = LeftRightLexCount.new
  @missing = nil
end

Public Instance Methods

call() click to toggle source

# File lib/syntax_suggest/explain_syntax.rb, line 46
def call
  @code_lines.each do |line|
    line.lex.each do |lex|
      @left_right.count_lex(lex)
    end
  end

  self
end

errors() click to toggle source

Returns an array of syntax error messages

If no missing pairs are found it falls back on the original ripper error messages

# File lib/syntax_suggest/explain_syntax.rb, line 95
def errors
  if missing.empty?
    return RipperErrors.new(@code_lines.map(&:original).join).call.errors
  end

  missing.map { |miss| why(miss) }
end

missing() click to toggle source

Returns an array of missing elements

For example this:

ExplainSyntax.new(code_lines: lines).missing
# => ["}"]

Would indicate that the source is missing a ‘}` character in the source code

# File lib/syntax_suggest/explain_syntax.rb, line 65
def missing
  @missing ||= @left_right.missing
end

why(miss) click to toggle source

Converts a missing string to an human understandable explanation.

Example:

explain.why("}")
# => "Unmatched `{', missing `}' ?"

# File lib/syntax_suggest/explain_syntax.rb, line 77
def why(miss)
  case miss
  when "keyword"
    "Unmatched `end', missing keyword (`do', `def`, `if`, etc.) ?"
  when "end"
    "Unmatched keyword, missing `end' ?"
  else
    inverse = INVERSE.fetch(miss) {
      raise "Unknown explain syntax char or key: #{miss.inspect}"
    }
    "Unmatched `#{inverse}', missing `#{miss}' ?"
  end
end