class SyntaxSuggest::ExplainSyntax - Documentation for Ruby 3.2

# 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