ECMAScript4MPS

ECMAScript4MPS started as an implementation of the ECMAScript 5.1 for JetBrains MetaProgrammingSystem, a.k.a. MPS. This version is still present and migrated regularly to the last version of MPS.

The development branch is in activy development and partially support ES6+ version. See implementation.md for informations about how the specifications have been implemented.

Introduction

The constructed AST is identical (with very small exceptions) to the one described by the Mozilla Parser API and implemented, for example, by parsers like Esprima. It's still quite incomplete being my focus on javascript generation. Read more on this announcement post.

Resources

• ECMAScript4MPS-discuss Google group.
• #ECMAScript4MPS on Twitter.

Try it out

• clone the github project.
• install MPS version 2018.3.1 .
• open the project with MPS.
• rebuild the project.
• the sandbox solution contains a complete javascript example I use to test the language and the generation to text.

Build the plugin

If for instance you have installed MPS in /opt/MPS/MPS-2018.3/, execute:

$ ant -Dartifacts.mps=/opt/MPS/MPS-2018.3/  assemble

The last message of the build process will tell you where the zip file with the plugin is.

An EcmaScript4MPS plugin

To get a pre-prepared and packaged ecmaScript4mps language you can install the IDEA/MPS plugin in either IntelliJ IDEA or MPS and start using the language right-away.

Future improvements

ECMAScript4MPS is rather primitive with respect to its editing capabilities that are still "AST like" and not "text like". Also it's missing almost all "lexer like" rules.

My objective is to generate javascript so a "text like" editor experience while editing ECMAScript4MPS models is out of scope. Nevertheless I think to further improve the editor while I'll be using it.

Writing a developer's guide that could help other developers understanding MPS is also one of my goals.

Notes about version ES2015 and ES2016

Reference specifications:

• ES2015
• ES2016

Rule parameters

Production rules can have parameters in the for of [Parameter], e.g. [Default], and each production can call other productions with or without one or more parameters.

Identifiers sec 12.1

Identifier has been specialized and is used only in other *Identifier productions.
IdentifierName is implemented as a string with checking rules.

Productions that use Identifier have been ideally simplified like:

BindingIdentifier[Yield]:
  IdentifierName but not ReservedWord   <-- instead of Identifier.
  [~Yield]yield

I've introduced IdentifierName bacause it's used not only in *Identifier productions. For instance is used in PropertyName.

TODO: modify *Identifier to use JSIdentifierName instead of INamedConcept, this way the check isValidIdentifierName() is done only in JSIdentifierName.

Implementation

• use JSIdentifiersUtils.isValidIdentifier() to check an Identifier.
• use JSIdentifiersUtils.isValidIdentifierName() to check an IdentifierName.
• the other concepts JS*Identifier have their own checking rules.

FunctionBody

I'll move { and } in FunctionDeclaration, that is already a concrete concept, so I can implement ConciseBody using an interface. I've checked the use of FunctionDeclaration and it's used always with braces.