Adding a New Package to the Build

New packages intended for distribution to end users should generally be added as a dependency of a “top-level product:” these are the roots of the LSST package hierarchy. They include lsst_apps, lsst_distrib, qserv_distrib and lsst_sims.

Before adding a new dependency to any of these products, it must be approved through the RFC process. Consensus must be reached regarding both the name and the suitability of the new package. Before adopting the RFC, the following steps must be completed:

  • Implementation tickets are created to cover package creation.

  • The package is migrated to the lsst org, if not already there.

  • An audit is done of any dependencies with a focus on identifying implied dependencies.

Packages that will not be distributed as part of a release do not require an RFC.

After approval, code written internally by Data Management should be packaged following the template in the lsst/templates repository. DM packaging of third party code should proceed as described in Distributing Third-Party Packages with EUPS.

New packages must be added to the LSST organization on GitHub. The simplest way to do this is to send a “create project” Slack message to @sqrbot-jr and select “LSST EUPS package” as the project type.

Access to the repository must be granted by a repository administrator to appropriate teams. For DM-written code, these include “Data Management” and “Overlords.” For third-party code, either forked or packaged as “TaP” tarball-and-patch, use the “DM Externals” and “Overlords” (but not “Data Management”) teams. Note that the “DM Auxilliaries” [sic] team is used to mark packages that are not part of the release distribution; it is used to tag them alongside the release as well as to catch accidental inclusions. The roles assigned to these teams should typically be “Write” for “Data Management”, “Admin” for “Overlords”, and “Read” for all others, but most permissions are handled at the organization level, so these could even be “Read” for all teams.


Failing to assign a team will break the daily and weekly builds. The automated builds use the team membership to determine the type of tag to be applied. Having the code reside in the lsst or lsst-dm organization on GitHub is not sufficient.

The new package must be added to the etc/repos.yaml file in the lsst/repos repository along with its corresponding GitHub URL. This file is governed by a “self-merge” policy: upon opening a pull request, it will be checked by GitHub Actions, and developers may merge without further review on success. This change must be merged before the package can be built on Jenkins. Refer to RFC-75 for background.

The new package then needs to be added to the ups/*.table file (and possibly the ups/*.cfg file if this is a C++ package) of one or more other packages in the stack where it is used so that the build system can work out the correct dependency tree. Table files should use setupRequired(package_name) or setupOptional(package_name) as necessary; test data packages are usually optional to allow releases to be made without requiring large additional data packages to be included. Packages that use optional dependencies must be written to ensure that they can pass their unit tests when the package is not available.

If the new package needs a distinct Jira component (most will), any DMLT member (such as your manager) can add one.

Configuring GitHub Repositories

All LSST DM repositories on GitHub must be configured by a repository administrator to protect the main branch and to ensure that the merge button for pull requests can not be pushed without the branch being up to date with main. There are a number of settings required to ensure this and they are described below with URLs referring to the afw package. Replace afw with the relevant package name to get to the correct page on GitHub.

  1. On the main settings page for the repository,, disable squash and rebase merging, and enable automatic deletion of head branches after merging a pull request:



If the Settings tab is not visible at the top of the repo page, an administrator likely needs to grant admin privileges first.

2. Configure the main branch to enable protections. For afw this is located at and can also be found from the “Branches” sidebar item on the settings screen. In the “Branch protection rules” section of that page you will have to click on “Add rule” to create a rule for main. First, add in main as the branch name pattern. Second, enable Require a pull request before merging, but disable Require approvals. Third, enable status checks, require that branches be up to date before merging, and add the lint GitHub action to the list of required status checks. To enable the lint GitHub action, type lint into the search box and select the lint GitHub action. Finally, include Administrators in these protections, since it’s all too easy to make a mistake without realizing you have special override powers. With checks enabled people will be able to use the GitHub merge button on Pull Requests and know that the standard process is being adhered to.

Once the above settings have been configured correctly, click CREATE to save the new rule. The new rule settings should look something like this:


GitHub requires that at least one check runs before the up-to-date checks are enabled, so a GitHub Action must be provided if the GitHub merge button is to be used. GitHub Actions do not replace normal testing done with a Jenkins job. For packages that contain Python, it is useful to add a simple GitHub Action by selecting “Actions” from the GitHub repository page, selecting “New Workflow” if necessary, and choosing the “LSST DM Python lint Workflow”. If Python typing is used, it can be checked using mypy via the “LSST DM Python mypy Workflow”. Similarly, YAML files can be checked via the “LSST DM YAML lint Workflow”, and shell scripts can be checked via the “LSST DM shellcheck Workflow”. (All of these checks can be configured, either via an external file such as .yamllint.yaml, or via modifications to the workflow as described in the link in the shellcheck workflow.) If nothing seems appropriate, the “LSST DM null Workflow” should be enabled to allow GitHub to do the checks it needs.

Pull requests will automatically run GitHub Actions and their results will be visible in the “Checks” tab of the pull request on GitHub.

Handling Git LFS-backed repos

New Git LFS-backed repos (or existing repos being converted to LFS) require additional configuration.

  • The repos.yaml entry must declare that the repository is LFS backed:

      lfs: true

    See the comment block at the top of repos.yaml for additional details.

  • At present, the EUPS distrib packaging mechanism does not support LFS-backed repos. These products must not be added to any top-level meta-package or as a mandatory (non-optional) recursive dependency of a top-level package.

  • Optional dependencies must be added to manifest.remap to prevent the creation of broken EUPS distrib packages. Please note that the “self-merge” policy (RFC-75) does not apply to manifest.remap.

    Unlike changes merged into repos.yaml, modifications to manifest.remap do not take immediate affect.

    We recommend that you attach the modification PR to a DM Jira issue on the Continuous Integration component.


LFS-backed repositories must always be used as optional dependencies and must always be added to the manifest.remap file. This is required because of constraints imposed by the EUPS publication mechanism.