Adding New Libraries

We do not yet have a packaging system, so this document lays out how we currently handle inter-library dependencies.

Adding a Git Submodule

The current way of handling inter-library dependencies is to use git submodules. This allows you to specify a precise version that you rely upon, but assumes that we’re all using git.

We tend to keep all git submodules in a top level directory within the repository named ext. To add a new submodule:

git submodule add <repository url> ext/<name>

The repository url should be a publicly accessible URL, so it is recommended to use either the git or https protocols (git:// or https://) rather than SSH (git@).

The name should be the name of the repository.

For example, to add the tracing library as a submodule, one would:

git submodule add https://github.com/dylan-foundry/tracing.git ext/tracing

Updating a Git Submodule

If the submodule has been updated to point at a new revision, after you do a git pull, you will want to update your submodules:

git submodule update --init --recursive

If you want to update the submodule to point to a new revision, then you would:

cd ext/<name>
git pull --ff-only origin master
cd ../..
git add ext/<name>
git commit -m 'Updated <name>.'

Setting Up Registry Entries

For each library that you add as a submodule, you will need to create a registry entry so that the Open Dylan compiler can find the library. See Using Source Registries for more detail.

In the case of the tracing library, you would create a new file, registry/generic/tracing-core, with the contents:

abstract://dylan/ext/tracing/tracing-core/tracing-core.lid

You can usually get a good idea for what registry entries are needed by looking into the registry directory of the library that you’re using.

Transitive Dependencies

The Dylan compiler won’t find transitive dependencies, so you will need to create registry entries for them as well.

Sometimes, you will want to create git submodules for them as well, but other times you can just reference them from the version that was pulled in with the existing submodule.

As an example, if you pull in the HTTP library, it has a number of submodules, so you don’t need to pull each of those in directly, but can reference them through the ext/http/ directory. (Note in this case that the http library uses a non-standard name for the directory holding its submodules.)