unparser
Generate equivalent source for ASTs from whitequarks parser.
The following constraints apply:
- No support for macruby extensions
- Only support for the modern AST format
- Only support for Ruby >= 2.5
It serves well for mutant mutators and the in-memory vendoring for self hosting, and other tooling.
Public API:
While unparser is in the 0.x
versions its public API can change any moment.
I recommend to use ~> 0.x.y
style version constraints that should give the best mileage.
Usage
require 'parser/current'
require 'unparser'
ast = Unparser.parse('your(ruby(code))')
Unparser.unparse(ast) # => 'your(ruby(code))'
To preserve the comments from the source:
require 'parser/current'
require 'unparser'
ast, comments = Unparser.parse_with_comments('your(ruby(code)) # with comments')
Unparser.unparse(ast, comments) # => 'your(ruby(code)) # with comments'
Passing in manually constructed AST:
require 'parser/current'
require 'unparser'
module YourHelper
def s(type, *children)
Parser::AST::Node.new(type, children)
end
end
include YourHelper
node = s(:def,
:foo,
s(:args,
s(:arg, :x)
),
s(:send,
s(:lvar, :x),
:+,
s(:int, 3)
)
)
Unparser.unparse(node) # => "def foo(x)\n x + 3\nend"
Note: DO NOT attempt to pass in nodes generated via AST::Sexp#s
, these ones return
API incompatible AST::Node
instances, unparser needs Parser::AST::Node
instances.
Equivalent vs identical:
require 'unparser'
node = Unparser.parse(<<~'RUBY')
%w[foo bar]
RUBY
generated = Unparser.unparse(node) # ["foo", "bar"], NOT %w[foo bar] !
code == generated # false, not identical code
Unparser.parse(generated) == node # true, but identical AST
Summary: unparser does not reproduce your source! It produces equivalent source.
Testing:
Unparser currently successfully round trips almost all ruby code around. Using MRI-2.5.x. If there is a non round trippable example that is NOT subjected to known Limitations. please report a bug.
On CI unparser is currently tested against rubyspec with minor excludes.
Limitations:
Source parsed with magic encoding headers other than UTF-8 and that have literal strings. where parts can be represented in UTF-8 will fail to get reproduced.
A fix is possible as with latest updates the parser gem carries the information.
Example:
Original-Source:
# -*- encoding: binary -*-
"\x98\x76\xAB\xCD\x45\x32\xEF\x01\x01\x23\x45\x67\x89\xAB\xCD\xEF"
Original-AST:
(str "\x98v\xAB\xCDE2\xEF\x01\x01#Eg\x89\xAB\xCD\xEF")
Generated-Source:
"\x98v\xAB\xCDE2\xEF\x01\x01#Eg\x89\xAB\xCD\xEF"
Generated-AST:
(str "\x98v\xAB\xCDE2\xEF\u0001\u0001#Eg\x89\xAB\xCD\xEF")
Diff:
@@ -1,2 +1,2 @@
-(str "\x98v\xAB\xCDE2\xEF\x01\x01#Eg\x89\xAB\xCD\xEF")
+(str "\x98v\xAB\xCDE2\xEF\u0001\u0001#Eg\x89\xAB\xCD\xEF")
Installation
Install the gem unparser
via your prefered method.
People
Various people contributed to this repository. See Contributors.
Contributing
- Fork the project.
- Make your feature addition or bug fix.
- Add tests for it. This is important so I don't break it in a future version unintentionally.
- Commit, do not mess with Rakefile or version (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
- Send me a pull request. Bonus points for topic branches.
License
See LICENSE file.