Ruby 3.1 will ship with this gem and it will automatically be required when a Ruby process starts up. No special setup is required.
Note: This gem works only on MRI and requires Ruby 3.1 or later because it depends on MRI's internal APIs that are available since 3.1.
1.time {}
$ ruby test.rb
test.rb:1:in `<main>': undefined method `time' for 1:Integer (NoMethodError)
1.time {}
^^^^^
Did you mean? times
def extract_value(data) data[:results].first[:value] end
When data is { :results => [] }, the following error message is shown:
$ ruby test.rb
test.rb:2:in `extract_value': undefined method `[]' for nil:NilClass (NoMethodError)
data[:results].first[:value]
^^^^^^^^
from test.rb:5:in `<main>'
When data is nil, it prints:
$ ruby test.rb
test.rb:2:in `extract_value': undefined method `[]' for nil:NilClass (NoMethodError)
data[:results].first[:value]
^^^^^^^^^^
from test.rb:5:in `<main>'
Note: This API is experimental, may change in future.
You can use the ErrorHighlight.spot method to get the snippet data.
Note that the argument must be a RubyVM::AbstractSyntaxTree::Node object that is created with keep_script_lines: true option (which is available since Ruby 3.1).
class Dummy def test(_dummy_arg) node = RubyVM::AbstractSyntaxTree.of(caller_locations.first, keep_script_lines: true) ErrorHighlight.spot(node) end end pp Dummy.new.test(42) # <- Line 8 # ^^^^^ <- Column 12--17 #=> {:first_lineno=>8, # :first_column=>12, # :last_lineno=>8, # :last_column=>17, # :snippet=>"pp Dummy.new.test(42) # <- Line 8\n"}
If you want to customize the message format for code snippet, use ErrorHighlight.formatter= to set your custom object that responds to message_for method.
formatter = Object.new def formatter.message_for(spot) marker = " " * spot[:first_column] + "^" + "~" * (spot[:last_column] - spot[:first_column] - 1) "\n\n#{ spot[:snippet] }#{ marker }" end ErrorHighlight.formatter = formatter 1.time {} #=> # # test.rb:10:in `<main>': undefined method `time' for 1:Integer (NoMethodError) # # 1.time {} # ^~~~~ # Did you mean? times
Occasionally, you may want to disable the error_highlight gem for e.g. debugging issues in the error object itself. You
can disable it entirely by specifying --disable-error_highlight option to the ruby command:
$ ruby --disable-error_highlight -e '1.time {}' -e:1:in `<main>': undefined method `time' for 1:Integer (NoMethodError) Did you mean? times
Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/error_highlight.
The gem is available as open source under the terms of the MIT License.