# NAP 0 — Purpose and Process¶

Author

“Juan Nunez-Iglesias <mailto:jni@fastmail.com>”

Author

“Andy Sweet <mailto:andrewdsweet@gmail.com>”

Author

“Kevin Yamauchi <mailto:kevin.yamauchi@gmail.com>”

Created

‘2022-03-23’

Status

Active

Type

Process

## What is a NAP?¶

NAP stands for Napari Advancement Proposal. A NAP is a design document providing information to the community, or describing a new feature for napari, its processes, or its environment. (See “Scope of NAPs”, below.) The NAP should provide a rationale for the proposed change as well as a concise technical specification, if applicable.

We intend NAPs to be the primary mechanisms for proposing major new features, for collecting community input on an issue, and for documenting the design decisions that have gone into napari. The NAP author is responsible for building consensus within the community and documenting dissenting opinions.

Because the NAPs are maintained as text files in a versioned repository, their revision history is the historical record of the feature proposal 1.

### Scope of NAPs¶

The napari project has grown in scope beyond just the software living in the github.com/napari/napari repository. It includes several other software packages such as npe2 (napari plugin engine 2), superqt, and magicgui, tools for the community such as the cookiecutter napari plugin, a webpage, and a chat forum, among others.

Additionally, napari sits at the center of a much broader community of users, plugin developers, educators, and downstream or helper libraries.

The scope of NAPs is not strictly defined. Certainly, any controversial decisions about code changes to the main napari software should be documented in a NAP. (See “When is a NAP warranted?”, below.) Changes to related libraries in the napari organization may or may not need a NAP, depending on how much the change would impact the main napari software. Changes to upstream dependencies outside of the napari organization, such as the napari-hub, fall under the governance of their respective organizations.

In some cases, the authors of external software or APIs may plan to make a change that affects the napari community, and may want the feedback of the napari developers and broader community. They may then choose to create a NAP as a way to document the plan, solicit feedback, and record the feedback and any final decisions. In general, the napari developers encourage and appreciate such engagement with the community as a way to build consensus and drive the ecosystem forward, together.

### When is a NAP warranted?¶

Most contributions to napari should go through the standard contributing process, that is, opening a pull request to the main repository. They will typically be uncontroversial improvements, and require little design discussion. The git commit and the pull request itself serve as an adequate record of the contribution’s history.

In some cases, contributions will require extensive discussions around any new APIs, breaking of existing APIs, changing of governance, build, or contributing mechanisms, or other aspects of the project. These might happen both on the NAP pull request (PR) itself and on other channels, such as Zulip, community meetings, or even one on one discussions. In such situations, the PR will not contain sufficient information to document all the considerations that went into a decision. Core developers may at their discretion then call for a NAP to summarize the discussion to date.

In addition to the above situation, napari is the product of many historical decisions that were not explained by a NAP. In some situations, community members might be confused about parts of napari’s design, and whether alternate designs were considered and rejected, or simply not considered. It might then be useful to write a retrospective informational NAP to explain that aspect of the project.

### Types of NAPs¶

There are three kinds of NAPs:

1. A Standards Track NAP describes a new feature or implementation for napari.

2. An Informational NAP describes a napari design issue, or provides general guidelines or information to the napari community, but does not propose a new feature. Informational NAPs do not necessarily represent a napari community consensus or recommendation, so users and implementers are free to ignore Informational NAPs. They may however be used to build consensus around conventions or practices. As an example, PEP-257 is an informational PEP describing formatting and grammar conventions for docstrings. It specifies that the first line of docstrings should be a complete one-line summary of the functionality of the function or class. Because the Python standard library and many other packages follow this PEP, Jupyter built the functionality of pressing Shift-TAB to display just one line of the docstring of the item under the cursor.

3. A Process NAP describes a process surrounding napari, or proposes a change to (or an event in) a process. Process NAPs are like Standards Track NAPs but apply to areas other than the napari library itself. They may propose an implementation, but not to napari’s codebase; they require community consensus. Examples include procedures, guidelines, changes to the decision-making process, and changes to the tools or environment used in napari development. Any meta-NAP is also considered a Process NAP.

## NAP Workflow¶

The NAP process begins with a new idea for napari. A NAP should contain a single key proposal or new idea. Small enhancements or patches often don’t need a NAP and can be injected into the napari development workflow with a pull request to the napari repo. The more focused the NAP, the more likely it is to be accepted.

Each NAP must have a champion—someone who writes the NAP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The NAP champion (a.k.a. Author) should first attempt to ascertain whether the idea is suitable for a NAP. Posting to the napari [issues list] is the best way to do this.

The proposal should be submitted as a draft NAP via a GitHub pull request to the docs/source/naps directory with the name nap-<n>-<short-title>.md where <n> is an appropriately assigned number (typically sequential) and <short-title> is a one or two word title for the idea (e.g., nap-35-lazy-slicing.md). The draft must use the NAP-X — Template and Instructions file.

Once the PR is in place, the NAP should be announced on various channels for discussion, including the #naps channel on Zulip and, if the NAP has significant user implications, on the image.sc forum.

At the earliest convenience, the PR should be merged (regardless of whether it is accepted during discussion). A NAP that outlines a coherent argument and that is considered reasonably complete should be merged optimistically, regardless of whether it is accepted during discussion. Additional PRs may be made by the author to update or expand the NAP, or by maintainers to set its status, discussion URL, etc.

Standards Track NAPs consist of two parts, a design document and a reference implementation. It is generally recommended that at least a prototype implementation be co-developed with the NAP, as ideas that sound good in principle sometimes turn out to be impractical. Often it makes sense for the prototype implementation to be made available as a PR to the napari repo, as long as it is properly marked as WIP (work in progress).

### Review and Resolution¶

NAPs are discussed in Zulip, on image.sc, and on GitHub. The possible paths of the status of NAPs are as follows:

All NAPs should be created with the Draft status.

The author of the NAP should periodically update the NAP with new points both against and in favor of the NAP raised in discussion.

Eventually, after discussion, there may be a consensus that the NAP should be accepted – see the next section for details. At this point the status becomes Accepted.

Once a NAP has been Accepted, the reference implementation must be completed. When the reference implementation is complete and incorporated into the main source code repository, the status will be changed to Final.

To allow gathering of additional design and interface feedback before committing to long term stability for a feature or API, a NAP may also be marked as “Provisional”. This is short for “Provisionally Accepted”, and indicates that the proposal has been accepted for inclusion in the reference implementation, but additional user feedback is needed before the full design can be considered “Final”. Unlike regular accepted NAPs, provisionally accepted NAPs may still be Rejected or Withdrawn even after the related changes have been included in a release.

Wherever possible, it is considered preferable to reduce the scope of a proposal to avoid the need to rely on the “Provisional” status (e.g. by deferring some features to later NAPs), as this status can lead to version compatibility challenges in the wider ecosystem.

A NAP can also be assigned status Deferred. The NAP author or a core developer can assign the NAP this status when no progress is being made on the NAP.

A NAP can also be Rejected. Perhaps after all is said and done it was not a good idea. It is still important to have a record of this fact. The Withdrawn status is similar—it means that the NAP author themselves has decided that the NAP is actually a bad idea, or has accepted that a competing proposal is a better alternative.

When a NAP is Accepted, Deferred, Rejected, or Withdrawn, the NAP should be updated accordingly. In all cases except Deferred, the Resolution header should also be added with a link to the relevant post on the discussion forum. Additional links and information may be added to the Discussion section of the NAP.

NAPs can also be Superseded by a different NAP, rendering the original obsolete. The Replaced-By and Replaces headers should be added to the original and new NAPs respectively.

Process NAPs may also have a status of Active if they are never meant to be completed, e.g. NAP 0 (this NAP).

### How a NAP becomes Accepted¶

Generally, a NAP is Accepted by consensus of all interested contributors. We therefore need a concrete way to tell whether consensus has been reached. When you think a NAP is ready to be accepted, start a topic on the Zulip naps channel with a subject like:

Proposal to accept NAP #<number>: <title>

In the body of the topic, you should:

• link to the latest version of the NAP,

• briefly describe any major points of contention and how they were resolved,

• include a sentence like: “If there are no substantive objections within 7 days from this post, then the NAP will be accepted; see NAP 0 for more details.”

For an equivalent example in the NumPy library, see: https://mail.python.org/pipermail/numpy-discussion/2018-June/078345.html

After you write the post, you should make sure to link to the specific thread from the Discussion section of the NAP, so that people can find it later.

Generally the NAP author will be the one to make this post, but anyone can do it – the important thing is to make sure that everyone knows when a NAP is on the verge of acceptance, and give them a final chance to respond. If there’s some special reason to extend this final comment period beyond 7 days, then that’s fine, just say so in the post. You shouldn’t do less than 7 days, because sometimes people are traveling or similar and need some time to respond.

In general, the goal is to make sure that the community has consensus, not provide a rigid policy for people to try to game. When in doubt, err on the side of asking for more feedback and looking for opportunities to compromise.

If the final comment period passes without any substantive objections, then the NAP can officially be marked Accepted. You should send a follow-up post notifying the thread (celebratory emoji optional but encouraged 🎉✨), and then update the NAP by setting its :Status: to Accepted, and its :Resolution: header to a link to your follow-up post.

If there are substantive objections, then the NAP remains in Draft state, discussion continues as normal, and it can be proposed for acceptance again later once the objections are resolved.

In unusual cases, when no consensus can be reached between core developers, the napari Steering Council may be asked to decide whether a controversial NAP is accepted, according to our governance.

### Maintenance¶

In general, Standards track NAPs are no longer modified after they have reached the Final state, as the code and project documentation are considered the ultimate reference for the implemented feature. They may, however, be updated under special circumstances.

Process NAPs may be updated over time to reflect changes to development practices and other details. The precise process followed in these cases will depend on the nature and purpose of the NAP being updated.

## Format and Template¶

NAPs are UTF-8 encoded text files using the MyST markdown format. Please see the NAP-X — Template and Instructions file and the MyST markdown cheat sheet for more information. We use Sphinx to convert NAPs to HTML for viewing on the web 2.

### Header Preamble¶

Each NAP must begin with a header preamble. The headers must appear in the following order. Headers marked with * are optional. All other headers are required.

  :Author: <list of authors' real names and optionally, email addresses>
:Status: <Draft | Provisional | Active | Accepted | Deferred | Rejected |
Withdrawn | Final | Superseded>
:Type: <Standards Track | Process>
:Created: <date created on, in yyyy-mm-dd format>
* :Requires: <nap numbers>
* :napari-Version: <version number>
* :Replaces: <nap number>
* :Replaced-By: <nap number>
* :Resolution: <url>


The Author header lists the names, and optionally the email addresses of all the authors of the NAP. The format of the Author header value must be

Random J. User <mailto:address@dom.ain>

if the email address is included, and just

Random J. User

if the address is not given. If there are multiple authors, each should be on a separate line.

## Acknowledgements¶

This process was based on existing process from the scikit-image (SKIPs), NumPy (NEPs), and Python (PEPs) projects.