What’s New in MPS 2023.2

A new launchtests Ant task is available with support for the following elements:

• library
• macro
• plugin
• testmodules

It supports the execution of all test artifacts, with the exception of JUnit 3, and serves as the new target for the test configuration build part.

• Any Java class appropriately annotated can be executed as a test.
• There is now only limited support for JUnit 4.
• Both in-process and spawned executions are possible.

This API allows you to extend the types of tests available in MPS, as well as implement listeners for test sessions.

Classes in jetbrains.mps.baseLanguage.unitTest.platform form the MPS test platform API:

JUnit 5 introduces, among other things, support for implementing tests that are executed with a custom engine. A popular example of such an engine is jqwik – a property-based testing framework.

In an earlier update, MPS received enhanced support for method references and the conversion of closures into Java lambdas. We’ve broadened this support with numerous minor features and bug fixes.

We previously introduced the diamond operator (new ArrayList<>()) for BaseLanguage constructors, but collection creators were excluded from this improvement. In this update, you can now omit type parameters from new collections, simplifying the code-writing process:

• Type inferred from initial values: var myList = new arraylist<> {myInitialValue}
• Type inferred from variable declaration: map<int, string> myMap = new hashmap<>

In addition, we’ve improved support for variance in collections. For example, it’s no longer possible to assign a ? extends Number notation. However, the type system will no longer object to the use of such bounded types when they are valid. The sequence<> type will remain covariant by default, as it won’t result in any unsafe consequences since you cannot insert it into a sequence of elements that are not of its type. This may bring new type-checking issues where unsafe code previously went undetected. These can be resolved with either bounded types list<? extends node<>> or sequence types sequence<node<>>.

For creating instances in an aspect model, MPS has so far followed a general logic that involved rootable non-abstract concepts, ordered by name or flag. Now optional configuration can be specified along with an aspect declaration, allowing language designers to control which concepts are presented to the user, as well as their grouping and ordering.

This confusing warning used to be shown when a ClassConcept extended or otherwise exposed its use of a ClassConcept from another module. Prior to version 2023.2, MPS relied on module dependencies specified in module descriptors to build the dependencies graph. Now that MPS builds the dependency information based on the actual generators and languages involved in transforming a model, you no longer need to specify these dependencies explicitly, hence there’s no more need for the check.

Sharing is a useful trait of any community. The following features have been implemented based on requests from the commercial MPS users who sponsored us developing them. Now, you can also take full advantage of these handy additions.

The model checker can now effectively utilize parallel hardware, thereby speeding up the process of model checking. Depending on the settings in Settings | Tools | Model Checker, it can spawn multiple threads when starting this process.

The FilePerRootDataSource.getStreamByName() method has been optimized to improve the performance of model data loading. If you use File-per-root persistence to store rather large models, this change will be noticeable.

While migrating a project using Ant tasks provided by MPS, dependencies may not get properly migrated. We added a flag to continue the migration of a project even in such cases. Stopping the migration process as soon as a non-migrated dependency is discovered remains the default behavior. To use this flag, add haltOnDependencyError="false" to your migrate Ant task.

In Settings / Preferences | Editor | Inspections, code samples now include syntax highlighting, which makes it easier to understand what triggers an inspection and decide whether you want it to be active or inactive.

The Fill Paragraph editor action is now supported for Markdown files, allowing you to break long texts into several lines of even length. To do this, set the caret inside the paragraph you want to edit and search for the Fill Paragraph command using Find Action (Ctrl+Shift+A).

We’ve improved the usability of the Branches popup. For instance, navigating between branches is now easier, as they are grouped and stored in expandable lists.

MPS 2023.2 provides auto-completion in the Create New Branch popup. Once you start typing a name for your new branch, the IDE will suggest relevant prefixes based on the names of existing local branches.

For every major release, we prepare instructions on how to migrate from older MPS versions to ensure everything goes smoothly. Please review them carefully.