MPS 2021.2 Help

MPS User's Guide

MPS User Guide for Language Designers

Welcome to MPS. This User Guide is a complete reference documentation to MPS and it will navigate you through the many concepts and usage patterns that MPS offers and will give you a hand whenever you need to know more details about any particular aspect of the system.

Topics

  1. Fundamental knowledge- a high-level overview of the basic notions
  2. Using MPS- get familiar with the interface through which you'll communicate with MPS
  3. Language definition  - defining a language involves specifying several aspects, each of which codifies some part of the language - the allowed AST structure, the appearance on the screen, type-system rules, etc.

    Aspect

    Description

    Core documentation

    Structure

    Defines the kinds of nodes (called Concepts) that may be used in user models. Each node in the program (model) refers to its concept. Concepts specify, which properties, children and references  nodes may have.  Concepts can extend other Concepts and implement ConceptInterfaces.

    Structure

    SModel language     - programatic access to the model

    Open API     - API reference for accessing models

    Quotations     - building AST snippets

    Pattern     - language for pattern matching nodes

    Using model & module dependencies from code FAQ

    Video -  Introduction to JetBrains MPS, The First Run: Projects

    Video -  Introduction to JetBrains MPS: Structure

    Constraints

    Restricts the relationships between nodes as well as the allowed values for properties beyond the rules defined in Structure.

    Constraints typicaly define:

     - the target scope for references (a collection of allowed nodes a reference can point to)

     - situations, in which a node can be a child/parent/ancestor of another node

     - allowed values for properties

     - property accessor methods (getters and setters)

    Constraints

    Scopes

    Video -  Introduction to JetBrains MPS, part 3: Constraints

    Behavior

    Just like classes in OOP hold methods, Concepts  may define methods and static methods that can be invoked on nodes in a polymorphic way. Nodes  thus carry behaviour alongside their properties and relationships.

    Behavior

    Video -  Introduction to JetBrains MPS, part 4: Behavior

    Editor

    Instead of defining a parser that would translate code from an editable form (i.e. text) into the tree-like structure that a computer could manipulate, MPS offers the concept of  projectional editor, which let's the user edit the AST directly. The Editor aspect enables language designers to create a UI for editing their concept concepts.

    Editor

    Diagramming Editor

    Transformation Menu Language

    Context Assistant

    Context actions tool

    Editor cookbook Editor language generation API

    Video -  Introduction to JetBrains MPS, part 5: Editor

    Actions

    The Actions  aspect provides means to specify advanced editor behavior, such as copy/paste or node initialization.

    Editor Actions

    Intentions

    All modern IDEs assist developers with instant code manipulating action available under a handy key-shortcut (Alt+Enter in MPS). Language authors can define such little code transformations for their languages in the Intentions  aspect.

    Intentions

    Video - Introduction to JetBrains MPS, part 7: Intentions

    Generator

    Models written in one or more languages get ultimately translated into runnable code in some target general-purpose language and platform, such as Java. Along the way models get gradually transformed so that repeatedly concepts get replaced with concepts from a lower level of abstraction until the bottom-line level is reached. The rules for translating concepts and their proper ordering is defined in the Generator  aspect.

    Generator

    Generator Plan

    Generator cookbook

    Building an interpreter cookbook

    Video -   Introduction to JetBrains MPS, part 8: Generator

    TextGen

    During code generation after the Generator  has reached the bottom-line AST representation, the TextGen  phase kicks in and translates all nodes in the model into their textual representation and saves the resulting textual source files on disk.

    TextGen

    Video -   Introduction to JetBrains MPS, part 9: TextGen

    Dataflow

    The ability to understand the flow of values and the flow of control through language constructs helps languages report issues such as  unreachable code  or  potential null-pointer error . Language designer can leverage the  Dataflow  aspect to define the flow for each concept, which MPS will then use to calculate the dataflow for the whole program.

    Dataflow

    Dataflow cookbook

    Video -   Introduction to JetBrains MPS, part 10: Dataflow

    Typesystem

    Language that need to type-check their code need to provide type-system rules. The MPS type-system engine will evaluate the rules on-the-fly, calculate types for nodes and report 

    errors, wherever the calculated type differs from the expectations. 

    So called  checking rules  may additionally be defined to verify non-typesystem assertions about the model.

    Typesystem

    Typesystem cookbook

    Using the typesystem

    Debugging the typesystem 

    Video -   Introduction to JetBrains MPS, part 11: Type-system

    Refactoring

    Modern IDEs allow the developer to seamlessly and flawlessly change the structure of their code through refactoring. MPS allows the language designers to prepare such refactorings and make them part of their languages.

    Refactoring

    Migrations

    When a new version of a language is released to the public, projects that use the previous version of the language must be migrated so that they use the new language constructs. Migration scripts, prepared by the language authors, will manipulate user code and automatically update it to the most recent version of the language.

    Migrations

    Migrations with branching

    Testing

    Various aspects of language definition can be automatically tested. Language authors may create tests that will verify that the editor, actions, type-system, data flow or constraints of their languages behave according to the specifications.

    Testing

    ScriptsTODOScripts

    Accessories

    The Accessories Models can be stored at two places - either as an aspect of a language (recommended), or as a regular model under a solution. In both cases, the model needs to be added to the Language Runtime Language Settings so as it could be used. A typical use case would be a default library of Concept instances to be available at any place the language is used.

    Accessories

  4. IDE Integration  - how to customise MPS, add language-specific visual extensions, use different persistence format, etc.
  5. IDE tools  - tools that MPS offers you to manipulate the languages
  6. Platform Languages  - out-of-the-box languages ready for use
  7. Building MPS projects  - building languages from the command line, Ant integration, continuous integration, creating and using plugins, obfuscating code
  8. Cookbooks  - quick how-to guides

  9. External tutorials and guides

 

Last modified: 14 September 2021