Improve experience of inter-project imports in local projects

[radeusgd]

Currently, we can easily import 'published' libraries like our Standard library.

The Enso library manager also has capabilities of importing local 'user' libraries, but it has not been used much and so is mostly unknown.

Recently, in #7521 we had a need to share testing logic between Tests and Table_Tests. To achieve this, the common code was moved to Standard.Test library which is shared. That is not desirable, because Standard.Test is a library for creating test suites and it should not itself contain such test suites.

We can fix this by allowing Table_Tests to import the Tests project as a library and import code from it.

To do so we need to:

• Extend the Table_Tests edition to make it aware of the enso_dev.Tests project.
  • This can be done either by adding a library override to the edition or setting prefer-local-libraries. I did the former as it seems cleaner.
  • One downside is - to be able to define a specific edition, we need to pin the edition version in the project - so for now I've pinned the version to 0.0.0-dev. Overriding edition settings is not compatible with the engine-version: default setting that we've been using (which has been technically deprecated).
    • That may not work with CI which seems to be running the tests with the 'current' version, e.g. overriding 0.0.0-dev to 2023.2.1-dev.
    • To fix that we may have to ensure SBT correctly overwrites the version there OR allow extends: default to extend the current default edition.
• Make sure that enso_dev.Tests is discoverable from Table_Tests. To achieve that, we need to ensure that test/Tests is on the ENSO_LIBRARY_PATH.
  • Easiest way to override the environment variable.
    • But that does not solve everything still - the library path requires to have format libraries/<namespace>/<name> but tests has format tests/<name> - missing the namespace part.
    • We need to change local library resolution to get rid of the prefix/namespace directory - the prefix should be checked by loading the package.yaml file and checking that instead. This way we can have a flat structure. We won't be able to have two local libraries with the same name next to each other but that seems to be less of a problem.
    • We need to update the docs to reflect the new structure. In particular:
      • https://github.com/enso-org/enso/blob/develop/docs/libraries/editions.md?plain=1#L192-L205
      • https://github.com/enso-org/enso/blob/develop/docs/libraries/sharing.md?plain=1#L30-L38
  • To avoid having to override the environment variable, we should modify the logic for detecting library paths to default to two paths: $ENSO_HOME/lib and the parent directory of the current project (currently only the former is accounted for).

[radeusgd]

I think once we could get through this, the example of importing Tests from Table_Tests in #7634 will serve as a nice example of how one can depend link Enso projects between each other.

[enso-bot]

Radosław Waśko reports a new STANDUP for yesterday (2023-08-28):

Progress: Updated behaviour of library resolution to allow importing Tests from within Table_Tests, added unit tests verifying the behaviour; documentation. Added a benchmark to Column.from_vector PR. Reviews. It should be finished by 2023-08-30.

Next Day: Next day I will be working on the #7238 task. Start work on Table.delete_rows.