Fix ArgumentError on escaping frozen String

[r7kamura]

Thank you @condor for creating this great gem! It's very convenient to format our application logs, but I have an idea that it would be even better if it supported frozen String values in its #dump implementation.

Problem

I use ltsv gem to format our chronological logs in our Rails application like this:

LTSV.dump(foo: "bar", time: Time.current)

Expected behavior

I think it should return a String like "foo:bar\ttime:2018-11-22 15:10:34 +0900" without any exception.

Actual behavior

But unfortunately the code above raises ArgumentError. This is because its implementation tries to mutate the given String by using String#gsub! to escape special characters.

Note: Time.current.to_s (ActiveSupport::TimeWithZone#to_s) returns a frozen String (since Rails 5.2.0), and LTSV#escape uses it.

ltsv/lib/ltsv.rb

Lines 134 to 139 in f545450

	value = string.kind_of?(String) ? string.dup : string.to_s
	value.gsub!("\\", "\\\\")
	value.gsub!("\n", "\\n")
	value.gsub!("\r", "\\r")
	value.gsub!("\t", "\\t")

• https://github.com/rails/rails/blob/v5.2.0/activesupport/lib/active_support/time_with_zone.rb#L1

Solution

To fix the problem above, I replaced String#gsub! with String#gsub.

I want to think there is no special reason to mutate given String here, but I'm afraid there might be a performance reason to choose String#gsub!. What do you think @condor?

[condor]

LGTM! Thanks for your contribution!

[r7kamura]

Thank you for the so quick response!
I'm looking forward to the new version of ltsv gem (v0.1.1 or v0.2.0?) ✨ 💎 ✨