# frozen_string_literal: true
require_relative "left_right_lex_count"
module SyntaxSuggest
# 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"
class ExplainSyntax
INVERSE = {
"{" => "}",
"}" => "{",
"[" => "]",
"]" => "[",
"(" => ")",
")" => "(",
"|" => "|"
}.freeze
def initialize(code_lines:)
@code_lines = code_lines
@left_right = LeftRightLexCount.new
@missing = nil
end
def call
@code_lines.each do |line|
line.lex.each do |lex|
@left_right.count_lex(lex)
end
end
self
end
# 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
def missing
@missing ||= @left_right.missing
end
# Converts a missing string to
# an human understandable explanation.
#
# Example:
#
# explain.why("}")
# # => "Unmatched `{', missing `}' ?"
#
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
# Returns an array of syntax error messages
#
# If no missing pairs are found it falls back
# on the original ripper error messages
def errors
if missing.empty?
return RipperErrors.new(@code_lines.map(&:original).join).call.errors
end
missing.map { |miss| why(miss) }
end
end
end
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