What's New in MPS 1.5

DSL debugger finally a part of MPS

One of the most important features in MPS 1.5 is a brand-new fully functioning DSL debugger. This debugger works with any language which can be reduced to MPS Base Language (Java). Now you can start debugging your application running either locally or remotely with just a single mouse-click. You can also add breakpoints into DSL code by pressing Ctrl+F8 or by clicking onto editor margin to the left of the corresponding code line.


Like in a usual debugger session, you can make use of step over/into/out actions, exploring and exporting threads list and stack traces, or browsing variables.


Variables No Custom View

Now MPS offers custom viewers for when you want to view some variables' values in a more domain-specific and convenient way. Viewers specify which values they show in a specific manner and how to show them. MPS provides a special language for creating custom viewers.

Custom View Collections

The Evaluate Expression dialog window, available by pressing Alt+F8, can run any DSL queries based on context object instance.


MPS 1.5 can debug any MPS Base Language (Java) code including various DSLs which reduce to MPS Base Language. In future versions we plan to finalize the API providing the possibility to debug any low-level languages other than Java.

Improved version control integration

MPS 1.5 features enhanced version control integration, with many new highlightings for model changes:

  • You can distinguish between added/modified model elements and unchanged model parts by looking at different coloring of project explorer tree nodes and editor tab labels.
  • Added and modified editor cells are highlighted with the background color.
  • Special markers in left and right editor margins are associated with added/removed/changed cells.
  • Left editor margin markers are clickable, so you can navigate to the next/previous change or revert the current one.

Generator language improvements

MPS introduced a new possibility to create pattern rules in its generator mapping configuration description. In some cases it's much more convenient to specify a simple model pattern instead of using a reduction rule with complex conditions. Declared pattern variables are available in subsequent model queries through the generation context parameter.

Pattern Rule

Now you can declare template-specific parameters in the MPS template declaration header. These parameters should be specified when calling the template either from rules in mapping configurations or from another template. You can also pass pattern variables declared in pattern rule as template parameters.

Template Parameters

Another useful generator feature is inline template with context: you can specify the template context for an inline template fragment just like in a standalone template declaration.

Inline Template With Context

Integration with existing languages

MPS 1.5 features a new language aspect, "stubs." Use this aspect to describe how to load existing code written in any programming language and convert it to MPS model. You can then reference this code from any program written in MPS. This new language aspect was used in MPS to describe java stubs loading to MPS Base Language entities, as well as GWT stubs.


Editor features

Similar to an ordinary Java IDE, MPS 1.5 tracks extends/implements references in Base Language classes. Based on this information, it displays "implementing" and "overridden" markers in the left editor margin displayed next to the class/interface/method declaration. Click these icons to navigate to the corresponding method; a pop-up menu will be displayed if there is more than one available action.

Overriden Method Markers

Code completion is an essential feature of any MPS-generated editor. Usually you start typing and then press Ctrl+Space to see completion suggestions; by default, only those suggestions that match the typed prefix will be shown. Now, you can press Ctrl+Space again to explicitly show ALL possible completion suggestions.

The latest MPS Editor definition contains several minor improvements, including:

  • Composite side-transform tag support. Use this when you need to associate more than one side-transform tag with the selected cell.
  • New CopyPreProcessor/CopyPostProcessor for additionally handling model elements while copying/pasting. *Processors can be defined in the actions language aspect.

MPS core languages improvements

MPS 1.5 introduces some useful changes to different MPS core languages, listed below by language. Please refer to MPS 1.5 documentation for more details.

Memory and performance improvements

Being a reasonably complex framework, MPS has high performance requirements which the MPS team is constantly working to lower. The current MPS upgrade contains a number of changes as well as some configuration options to achieve improved overall system performance, including:

  • faster start-up time
  • faster class reloading
  • reduced memory consumption

You can switch on/off the following code generator options:

  • Generate in parallel (available in Strict mode only)
  • Save generation dependencies (experimental) in this mode next code generation session will not include any model roots that weren't changed
  • Model generation performance report

Other improvements

MPS 1.5 also provides other improvements:


MPS source code repository is publicly available

MPS is an open-source project, and starting form version 1.5 it has a publicly available Git repository. Use it to check out the current development state, browse history, stay up to date with the latest features and fixes, and of course contribute your patches.

What's New in MPS 1.1

Analyze Stacktrace — One Step Closer to Debugger

We're actively working on a full-fledged MPS debugger and MPS 1.1 is only few steps away from it. If you have an exception that you want to check against your code, use Tools | Analyze Stacktrace. Paste the stacktrace into the opened tool-window and you can navigate from exception to MPS source code.

You can also click in stacktraces that occur while you run code or tests in MPS.

Analyze Stacktrace (click to see more) Analyze Stacktrace

This is made possible with a new debug information generator. When you generate a model, it produces a file which allows to find nodes in the generated code that correspond to a particular text position.

Run Configurations

Another important addition is Run Configurations. Run Configurations allow having multiple saved execution profiles for quick access. You can quickly select a configuration to run, directly from the main toolbar.

Add Run Configuration Edit Run Configuration

In configuration parameters you can specify what to run and the arguments arguments. Even more, MPS includes Run Configuration for base language main classes and unit tests, but you can, of course, create your own. MPS provides a DSL for creating custom run configurations.

Test Runner UI (click to see more) Test Runner UI

Additionally, MPS allows to run from context and auto-creates a corresponding configuration for the executed entity, either a module, a class, a method, etc.

Continuous Integration Using Model Generator Ant Task

Continuous Integration is a very important practice in software development. If you adopt it in your projects and want to use with MPS too, you are going to need a server-side model generator. MPS 1.1 adds a special Ant task for this purpose, and now it is possible to use it inside your CI solution (e.g. TeamCity).

General Improvements

We also optimized performance and memory usage. This is especially noticeable on large documents in the editor.

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