Opal Compiler

Opal is a source to source compiler. It accepts ruby code as a string and
generates javascript code which can be run in any environment. Generated
code relies on the opal runtime which provides the class system and some
other runtime helpers.

Compiler stages

The compiler can be broken down into 3 separate stages:

• lexing + parsing
• code generation

Lexer/Parser

The opal parser relies on the parser gem, see debug/development documentation there to know more about its internals: https://whitequark.github.io/parser/.

Code generation

The opal compiler takes these sexps from the parser
and generates ruby code from them. Each type of sexp has its own node type
used to generate javascript. Each node creates an array of one or more
fragments which are the concatenated together to
form the final javascript. Fragments are used as they contain the generated
code as well as a reference back to the original sexp which is useful for
generating source maps afterwards.