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# Usage in conjunction with the Prism Parser Translator
Because `parser` only parses Ruby <= 3.3 and `prism` only Ruby >= 3.3, if you want to continue parsing both old and new versions, you need to depend on both `parser` and `prism`.
## Using `prism` when parsing with an explicit Ruby verion
```rb
require 'parser'
require 'prism'
def parser_for_ruby_version(ruby_version)
case ruby_version
when 3.1
require 'parser/ruby31'
Parser::Ruby31
when 3.2
require 'parser/ruby32'
Parser::Ruby32
when 3.3
Prism::Translation::Parser33
when 3.4
Prism::Translation::Parser34
else
raise 'Unknown Ruby version'
end
end
parser_for_ruby_version(3.4).parse(<<~RUBY)
puts 'Hello World!'
RUBY
```
## Using `prism` when parsing ruby for the currently running Ruby version
If you are using `Parser::CurrentRuby`, you need to do similar branching logic:
```rb
def parser_for_current_ruby
if Gem::Version.new(RUBY_VERSION) <= '3.3'
require 'parser/current'
Parser::CurrentRuby
else
require 'prism'
# Only available on prism > 1.4.0
Prism::Translation::ParserCurrent
end
end
parser_for_current_ruby.parse(<<~RUBY)
puts 'Hello World!'
RUBY
```
## Using a custom builder
If you are providing a custom builder (see [Customization](./CUSTOMIZATION.md)), you must create a copy that behaves the same for `prism`, but inherits from a different base class. This is because the builder used internally by `prism` has more functionality for more modern node types, which is lacking in the builder from `parser`.
```rb
# Use a module to not duplicate the implementation
module BuilderExtensions
def self.inherited(base)
# Always emit the most modern format available
base.modernize
end
end
class BuilderParser < Parser::Builders::Default
include BuilderExtensions
end
class BuilderPrism < Prism::Translation::Parser::Builder
include BuilderExtensions
end
```
You can then conditionally use the proper builder class, branching on the version of ruby that will get analyzed.
## New node types
As new syntax gets added to Ruby, the `prism` gem may emit nodes that have no counterpart in the `parser` gem. These nodes will be documented [in the usual place](./AST_FORMAT.md) but are otherwise not supported or emitted by the `parser` gem.
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