Define Editions Configuration

[radeusgd]

Summary

We introduce the concept of editions and this task encompasses the related code that needs to be added to handle loading and using editions.

Value

• Editions can be used in the projects.

Specification

• Refine the design of the Edition file-format and document it.
  • The edition should include the engine version that is related to that edition and a list of available libraries along with their versions.
  • An edition may derive another edition - it then inherits all of its parent's settings but any settings set within the edition override what was inherited. The inheritance can be arbitrarily nested.
  • It can prefer-local-libraries.
  • Refer to a special local repository which points to the local libraries directory.
    • It should be configurable via an ENSO_LOCAL_LIBRARIES_DIR env var.
    • By default it should be ~/enso/libraries (or the equivalent for other OSes).
• Implement a parser for the edition file format and a system for loading editions from predefined localizations, including being able to load nested derived definitions.
  • The nested editions should be accessed using an EditionProvider.
  • The loader must correctly handle inheritance cycles (producing an error instead of entering an infinite loop).
• Implement an EditionProvider that gets a list of paths to the edition storage.
• Implement an EditionProvider that uses the DistributionManager to get the paths.
  • DistributionManager should be able to override the local and downloaded library paths based on environment variable.
• Implement a LibraryResolver that gets a path to the remote library storage and to local libraries.
  • Implement the logic which can load the edition by name and then resolve library versions.
    • libraryName -> Either[LibraryVersionResolutionError, LibraryVersion]
  • This may also be the right place to include the library path resolution logic.
    • (libraryName, libraryVersion) -> Either[LibraryPathResolutionError, Path]
• Update the Package Config to include the edition configuration and infer the engine version based on that.

Acceptance Criteria & Test Cases

• The above specification is completed.
• The edition file format is documented.
• Edition parsing together with loading derived editions and cycle avoidance are unit tested.
• The core logic for library resolution is tested.

[radeusgd]

Related discussion at #1771 (comment)

[radeusgd]

Note: this will include a breaking change of the package file format. The engine-version field will now be inside of the edition section and will be optional (as it can be defined in a parent edition).