Migration Assistant

Changes to languages, in particular, removing concepts or adding and removing concept properties, children, and references, introduce incompatibilities between the previous and the next language version.

This impacts language users when they update to the next version, as they may discover that their models no longer match the language definitions and see reported errors.

MPS tracks versions of languages used in projects and provides automatic migrations to upgrade the usages of a language to the most recent versions.

Whenever MPS detects that some models use an older version of a language, it will prompt the user to run the Migration assistant to update the models. The user can also invoke the Migration assistant manually from the menu Tools | Run Migration Assistant. Once invoked, the Migration assistant will collect all the automatic migration scripts that language authors have prepared for migrating user models and then safely run them. As soon as the Migration assistant finishes, the user models should be up-to-date.

The migration process consists of several steps. A special preparatory step called Re-save all models from project is always run first to ensure that all models are in a consistent state and to update ResolveInfo across the project. Changes from this action are accumulated in a single Local History and VCS changeset together with the migrations, which simplifies future code management.