Packaging

Once a release is cut, napari is distributed in two main ways:

• Packages: both to PyPI and conda-forge.

• Installers: bundles that include napari plus its runtime dependencies in a step-by-step executable.

Packages

Despite its numerous dependencies, napari itself is a regular Python project that can be packaged using established workflows.

PyPI packages

Creating and submitting the packages to PyPI (the repository you query when you do pip install) is handled in the make_release.yml workflow. Creation is handled with make dist (as specified in our Makefile) and submission is done using the official PyPA GitHub Action. This workflow will also create a GitHub release. See Release guide for more details.

conda-forge packages

Once the Python package makes it to PyPI, it will be picked up by the conda-forge bots. The bots will automatically submit a PR to the napari-feedstock repository within a few hours. This is all automated by the conda-forge infrastructure (see previous examples). We only need to check that the metadata in the recipe has been adjusted for the new release. Pay special attention to the runtime dependencies and version strings!

We keep a copy of the feedstock’s recipe in the napari/packaging repo, which is updated manually whenever a change to pyproject.toml is detected. Check the file conda-recipe/meta.yaml and make sure its outputs contents are synced to the napari-feedstock copy.

Once the conda-forge CI is passing and the PR is approved and merged, the final packages will be built on the default branch and uploaded to the conda-forge channel. Due to the staging steps and CDN synchronization delays, the conda packages can take up to 1h to be available after the merge.

Note

Check Release guide for more details about the conda-forge release process and maintenance tasks.

conda packaging split

We provide three different outputs in the conda package recipe:

• napari-base: This is the package that ships the actual source and data. The runtime requirements only include the basic functionality. This package is recommended as a dependency for plugins and other projects. Most end users will prefer the napari package, below, but this one may be useful for those wanting a more minimal environment.

• napari: This output is what most users want. It depends on napari-base, and adds optional yet recommended dependencies for (performant) GUI usage, like the plugin manager or numba. Note that the Qt backend is not included.

• napari-menu: Depends on napari, and ships the menuinst JSON file, in case you want a desktop shortcut to start the application easily. This is included as part of the bundled installers for convenience.

conda packages in the napari channel

The napari project also has a napari channel in anaconda.org. We mainly use it to provide:

• Nightlies built off of main, uploaded to the napari/label/nightly channel.

• Release candidates, uploaded to napari/label/rc.

Note

The napari channel happens to contain the final releases too. However, these are not meant to be used by end users, who should use conda-forge. The releases uploaded to our channel are the same ones we use to build our constructor installers (see below). Otherwise, we would have to wait for the conda-forge PR, which is only triggered by the PyPI release. That means we would not be able to create the installers in the same tagging event.

To do it in a conda-forge compatible way, we clone napari-feedstock and patch the source instructions to use the code from the repository branch. The version is also patched to match the setuptools-scm string. After re-rendering the feedstock, we run conda-build in the same way conda-forge would do and upload the resulting tarballs to our Anaconda.org channel.

Additionally, the tarballs are also passed as artifacts to the next stage in the pipeline: building the constructor installers (more below).

Installers

Once the packages have been built and uploaded to their corresponding repositories, we can bundle them along with their dependencies in a single executable that end users can run to install napari on their systems, with no prior knowledge of pip, conda, virtual environments, command line prompts or anything.

A software installer is usually expected to fulfill these requirements:

• It will install the application so it can be run immediately after.

• It will provide a convenient way of opening the application, like a shortcut or a menu entry.

• It will allow the user to uninstall the application, leaving no artifacts behind.

We use constructor to build the bundled installers, which takes conda packages. conda packages offer several advantages when it comes to bundling dependencies, since it makes very few assumptions about the underlying system installation. As a result, constructor bundles include libraries that might be missing in the target system and hence should provide a more robust user experience.

The automation is implemented in the .github/workflows/make_bundle_conda.yml workflow, which only specifies the triggers used to call the actual workflow implementation under the napari/packaging repository. This repository stores all the logic and files needed to create the nightly conda packages and the constructor installers.

constructor allows you to build cross-platform installers out of conda packages. It supports the following installer types:

• On Linux, a shell-based installer is generated; users can execute it with bash installer.sh.

• On macOS, you can generate both PKG and shell-based installers. PKG files are graphical installers native to macOS, so that’s the method we use with napari.

• On Windows, a graphical installer based on NSIS is generated.

The configuration is done through a construct.yaml file, documented here. We generate one on the fly in the build_installers.py script found in napari/packaging. For a hypothetical napari v1.2.3 we would have built this configuration file:

# os-agnostic configuration
name: napari
version: "0.0.1"  # this is the _internal_ version of the installer infrastructure
company: Napari
license: EULA.md
channels:
  # - local  # only in certain situations, like nightly installers where we build napari locally
  - conda-forge
specs: # specs for the 'base'  environment
  - python   # pinned to the version of the running interpreter, configured in the CI
  - conda    # we add these to manage different napari versions
  - mamba    # we add these to manage different napari versions
  - pip      # we add these to manage different napari versions
extra_envs:
  napari-1.2.3: # this is the environment that will actually contain the napari packages
    specs:
      - napari=1.2.3
      - napari-menu=1.2.3
      - python   # pinned to a specific version, configured by CI
      - pyside2  # pinned to a specific version, configured by CI
      - conda    # needed for the plugin manager
      - mamba    # needed for the plugin manager
      - pip      # needed for the plugin manager
menu_packages:
  - napari-menu  # don't create shortcuts for anything else in the environment

# linux-specific config
default_prefix: $HOME/napari-1.2.3  # default installation path

# macos-specific config
default_location_pkg : Library # first component of the default path under ~/
pkg_name: napari-1.2.3  # second component of the default path
installer_type: pkg  # otherwise, defaults to sh (Linux-like)
welcome_image: resources/napari_1227x600.png  # bg image with the napari logo on bottom-left corner
welcome_file: resources/osx_pkg_welcome.rtf  # rendered text in the first screen
conclusion_text: ""  # set to an empty string to revert constructor customizations back to system's
readme_text: ""  # set to an empty string to revert constructor customizations back to system's
signing_identity_name: "Apple Developer ID: ..."  # Name of our installer signing certicate

# windows-specific config
welcome_image: resources/napari_164x314.png  # logo image for the first screen
header_image:  resources/napari_150x57.png  # logo image (top left) for the rest of the installer
icon_image: napari/resources/icon.ico  # favicon for the taskbar and title bar
default_prefix: '%USERPROFILE%/napari-1.2.3'  # default location for user installs
default_prefix_domain_user: '%LOCALAPPDATA%/napari-1.2.3'  # default location for network installs
default_prefix_all_users: '%ALLUSERSPROFILE%/napari-1.2.3'  # default location for admin installs
signing_certificate: certificate.pfx  # path to signing certificate

The main OS-agnostic keys are:

• channels: where the packages will be downloaded from. We mainly rely on conda-forge for this, where napari is published. In CI, we locally build our own (development) packages for conda, without resorting to conda-forge. To make use of those (which are eventually published to the napari channel), we unpack the GitHub Actions artifact in a specific location that constructor recognizes as a local channel once indexed.

• extra_envs> napari-0.5.4: the environment that will actually contain the napari installation. In this key, you will find specs, which lists the conda packages to be installed in that environment. Constructor will perform a conda solve here to retrieve the needed dependencies.

• menu_packages: restrict which packages can create shortcuts. We only want the shortcuts provided by napari-menu, and not any that could come from the (many) dependencies of napari.

Then, depending on the operating systems and the installer format, we customize the configuration a bit more.

The bundled Python version in the installers follows the Python version installed in the CI make_bundle_conda.yml workflow at napari/packaging. Update the CI matrix configuration to bump the bundled Python. We use the oldest version supported by the SPEC-0 recommendations.

Default installation path

This depends on each OS. Our general strategy is to put the general installation under ~/<hidden>/napari-<VERSION>, which will eventually contain the napari installations under envs/, with environments named as napari-<VERSION>. However, there are several constrains we need to take into account to make this happen:

• On Windows, users can choose between an “Only me” and “All users” installation. This changes what we understand by “user directory”. This is further complicated by the existence of “domain users”, which are not guaranteed to have a user directory per se.

• On macOS, the PKG installer does not offer a lot of flexibility for this configuration. We will put it under ~/Library/napari-<VERSION>, by default.

This means that if you install napari=0.5.4 using the installer, the actual napari executable can be found, by default, on the following locations:

• Linux: ~/.local/napari-0.5.4/envs/napari-0.5.4/bin/napari

• macOS: ~/Library/napari-0.5.4/envs/napari-0.5.4/bin/napari`

• Windows: ~/napari-0.5.4/envs/napari-0.5.4/Library/bin/napari

Branding

Graphical installers can be customized with logos and icons. These images are stored under the resources/ directory (outside the source), except for the square logos/icons (which are stored under napari/resources/ so the shortcuts can find them after the installation).

Some steps are also configured to display a custom text, like the license or the welcome screen on macOS.

Signing

In order to avoid security warnings on the target platform, we need to sign the generated installer.

On macOS, once Apple’s Installer Certificate has been installed to a keychain and unlocked for its use, you can have constructor handle the signing via productsign automatically. However, this is not enough for a warning-free installation, since its contents need to be notarized and stapled too. For this reason, constructor has been modified to also codesign the bundled _conda executable (the binary provided by conda-standalone, see below) with the Application Certificate. Otherwise, notarization fails. After that, two actions take care of notarizing and stapling the resulting PKG.

On Windows, any Microsoft-blessed certificate will do. constructor allows us to specify a path to a PFX certificate and then have the Windows SDK signtool add the signature. Note that signtool is not installed by default on Windows (but it is on GitHub Actions). Right now, we simply reuse the Apple certificate just to sign the installer with something. Note that this certificate is not recognized by Windows as a valid one, so users will still get the SmartScreen warning. However, it will allow folks to check the signature metadata and see that it comes from napari.

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More details about our packaging infrastructure can be found in the NAP-2 document.

Details of the constructor stack

Generating a conda-based installer requires several components in place:

• constructor is the command-line tool that builds the installer.

  • It depends on conda to solve the specs request.

  • It also requires a copy of conda-standalone (a PyInstaller-frozen version of conda) to be present at build time so it can be bundled in the installer. This is needed because that conda-standalone copy will handle the extraction, linking and shortcut creation when the user runs the installer on their machine.

• menuinst handles the creation of shortcuts / desktop menu entries across all platforms.

  • conda depends on this library to handle shortcuts when packages are installed.

  • constructor delegates the shortcut creation to conda-standalone’s menuinst bundled copy at installation time.

    • For performance reasons, uninstalling the shortcut is done via a bundled script that calls menuinst directly.