The Spoofax Language Workbench

Spoofax is a platform for developing textual (domain-specific) programming languages. The platform provides the following ingredients:

  • Meta-languages for high-level declarative language definition
  • An interactive environment for developing languages using these meta-languages
  • Code generators that produces parsers, type checkers, compilers, interpreters, and other tools from language definitions
  • Generation of full-featured Eclipse editor plugins from language definitions
  • Generation of full-featured IntelliJ editor plugins from language definitions (experimental)
  • An API for programmatically combining the components of a language implementation

With Spoofax you can focus on the essence of language definition and ignore irrelevant implementation details.

Developing Software Languages

Spoofax supports the development of textual languages, but does not otherwise restrict what kind of language you develop. Spoofax has been used to develop the following kinds of languages:

Programming languages
Languages for programming computers. Implement an existing programming language to create an IDE and other tools for it, or design a new programming language.
Domain-specific languages
Languages that capture the understanding of a domain with linguistic abstractions. Design a DSL for your domain with a compiler that generates code that would be tedious and error prone to produce manually.
Scripting languages
Languages with a special run-time environment and interpreter
Work-flow languages
Languages for scheduling actions such as building the components of a software system
Configuration languages
Languages for configuring software and other systems
Data description languages
Languages for formatting data
Data modeling languages
Languages for describing data schemas
Web programming languages
Languages for programming web clients or servers

Declare Your Language

We design Spoofax according to the following guiding principles:

Separation of concerns
Separate specification from implementation. Separate language-specific aspects from language-independent aspects. Separate definition of separate aspects (e.g. separate syntax definition and static semantics definition)
Single source
Instead of repeating a language aspect in many different implementation components, we aim to generate many different artifacts from a single source.
Declarative language definition
Language designers should focus on what distinguishes their language and should not be distracted by writing boilerplate for recurring implementation details. Rather than confronting each language designer with these implementation details, we factor them out into language-independent abstractions and corresponding implementations.

Following these guidelines, Spoofax provides the following high-level, declarative meta-languages:

The SDF3 Syntax Definition Formalism allows language designers to focus on the structure of programs rather than on debugging parser implementations by means of the following features: support for the full class of context-free grammars by means of generalized LR parsing, integration of lexical and context-free syntax through scannerless parsing, safe and complete disambiguation using priority and associativity declarations, an automatic mapping from parse trees to abstract syntax trees through integrated constructor declarations, automatic generation of formatters based on template productions, syntactic completion proposals in editors.
The NaBL2 ‘Name Binding Language’ supports the definition of the static semantics of languages including name binding and type analysis. NaBL2 rules define a mapping from abstract syntax trees to name and type constraints. The generated constraints are solved by a language-independent solver and produce error messages to display in an editor and a symbol table for the analyzed abstract syntax tree for use in further processing. Name analysis in NaBL2 is based on scope graphs, a language-independent model for name resolution and scoping.
The FlowSpec Data-Flow Analysis Specification Language supports the specification of control-flow and intra-procedural data-flow analysis. FlowSpec control-flow rules map abstract syntax trees to control-flow edges. Data-flow properties in FlowSpec represent the results of different data-flow analyses, and the analyses are specified through property rules per type of control-flow node. FlowSpec depends on the use of NaBL2 for name binding.
The Stratego transformation language supports the definition of transformations of abstract syntax terms using rewrite rules and programmable rewriting strategies. Strategies enable concise definition of traversals over trees. Stratego is used to define desugarings, transformations, optimizations, and code generation (translation to another language).
The DynSem Dynamic Semantics specification language supports the definition of the execution behavior of programs by means of reduction rules that are typically used to define natural semantics or big-step operational semantics. DynSem specifications are compiled to interpreters targeting the Truffle/Graal stack.
The SPT testing language supports the definition of tests for all aspects of a language definition.
The ESV editor services language is used to configure language definitions.

A Platform for Language Engineering

Spoofax is a platform for language engineers. That is, it provides full support for software engineering of language implementations.

Agile Language Development
An important feature of Spoofax is its support for agile language development. The development of a language definition and testing that language definition in the generated IDE for the language under development is done in the same Eclipse instance. This enables a quick turn-around time between language development and language testing.
IDE generation
Spoofax generates a full fledged editor plugin from a language definition.
Spoofax does not only provide an IDE for interactively developing and using languages, it also provides a programmatic interface that enables embedding languages and their implementations directly in application code or to invoke language components from build systems or the command line.
Bootstrapped Language Workbench
Spoofax has been bootstrapped. That is, Spoofax is used for the definition of its own meta-languages and the workbench is the composition of plugins generated for these meta-languages.
Continuous integration
The Spoofax sources are continuously built on a buildfarm at TU Delft, which reports build errors to Spoofax developers and provides a complete build for various platforms of the latest version.
Open source
Spoofax is open source and available under the Apache 2.0 license. The sources are maintained in the MetaBorg github organization; pull requests are welcome.

A Platform for Research

Spoofax is a platform for language engineering research. Due to its modular architecture it is easy to extend the workbench with new experimental meta-languages and tools. For example, the current version comes with an improved parser generator in addition to the old SDF2 parser generator, and it provides the NaBL2 static semantics specification language next to the old NaBL/TS solution.