symbol-fstring

symbol-fstring is a Ruby extension that provide access to symbols internal string representations.

Why?

In Ruby many APIs tend to accept symbols, but regularly convert them to string internally. The typical example is ActiveSupport::HashWithIndifferentAccess, but there are plenty more.

The problem with this is that Symbol#to_s creates a new string every time it is invoked, and since it often happens in hotspots, it causes a lot of work for the garbage collector, and cause many identical strings to be kept in memory.

There was an attempt to make Symbol#to_s return it's internal fstring for Ruby 2.7, but unfortunately it got reverted, and probably won't happen before a while.

Installation

Add this line to your application's Gemfile:

gem 'symbol-fstring'

And then execute:

$ bundle

Or install it yourself as:

$ gem install symbol-fstring

Usage

FString can be used in two ways.

`FString.patch_symbol!`

If your application and your dependencies are compatible with it, you can change Symbol#to_s behavior globally with:

FString.patch_symbol!

Or you can also add it this way in your Gemfile:

gem 'fstring', require: 'fstring/all'

`FString.to_s`

If you don't want to patch the core Symbol class, you can alternatively substitute some_symbol.to_s for FString.to_s(some_symbol) in your own code.

Benchmark

From benchmark/symbol-to_s

 Symbol#to_s (orig)     12.786M (± 1.5%) i/s -     64.032M in   5.009020s
FString.symbol_to_s     20.371M (± 1.7%) i/s -    101.981M in   5.007706s
       FString.to_s     19.086M (± 1.5%) i/s -     95.410M in   5.000016s
Symbol#to_s (patch)     21.669M (± 1.9%) i/s -    108.591M in   5.013331s

But there's also a reduced pressure on the garbage collector.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Shopify/symbol-fstring.

License

The gem is available as open source under the terms of the MIT License.

tb-ruby/symbol-fstring