The Enso RFC Process

Like any Open Source language, Enso welcomes interaction from the community, as we believe that only through the community’s suggestions and feedback can we make Enso the best it can be.

To this end, this repository defines a process to be followed for those people that want to make ‘substantial’ changes to the Enso language, the Enso compiler and runtime, or even this RFC process itself. What we define as a ‘substantial’ change is in flux based on community norms and in relation to the portion of the ecosystem being changed.

Substantial changes may thus include the following:

  • Semantic or syntactic changes to Enso that aren’t related to fixing a pre-existing bug.
  • Adding or removing language features.
  • Changes to the interface between the language and its standard library.
  • Additions to and removals from the standard library.

The following are examples of changes that do not need to follow the RFC process:

  • Refactoring of the compiler or libraries that does not change any semantics.
  • Additions or alterations that improve numerical metrics (e.g. performance improvements, error detection, ergonomics improvements).
  • Additions invisible to the users of the language (e.g. new APIs internal to the compiler that do not fall under the categories for ‘substantial’ changes listed above).

Before contributing an RFC, please ensure that you have read and agree with the licensing terms under which this repository operates, and that you have signed the CLA.

Creating an RFC

While informal, we do aim to provide a basic outline for the process of creating an RFC. The intention of this process is that RFCs arrive in a state with enough detail to spark discussion, and then evolve through discussion with all interested parties.

Before Creating an RFC

Keep in mind that a hastily-created RFC can hurt discussion and its chances of being accepted, even if the idea proposed is excellent! A half-baked proposal, a previously-rejected idea, or a feature that doesn’t align with our vision for Enso could be rejected swiftly, making the unprepared contributor feel demotivated. Doing a little bit of preparatory legwork can make the RFC process that much more smooth.

While there is no specific process for submitting an RFC, we do recommend that you talk to other members of the community to find out whether your proposal would have support, and fits with the broader vision for Enso as a whole.

If the idea receives encouraging feedback from the core team, as well as the community, it is an indication that the RFC is worth pursuing.

The RFC Process

To summarise the end goal of the RFC process, the aim is to merge the proposal (as a markdown file) into the RFC Repository. At this point, the RFC becomes ‘Active’, and may then be implemented.

If this is your first contribution to the Enso RFC process, please ensure that you have signed the Enso Contributor License Agreement.

The process for creating an RFC can be outlined as follows:

  1. Fork this repository.
  2. Copy to a new file, where my-proposal is a short and descriptive name for the feature.
  3. Fill in the RFC Template for your feature. Take care with the details as RFCs that don’t put thought into the design or its impacts, or are disingenuous about the drawbacks or alternatives are likely to meet a poor reception. One of the key points for considering RFCs is how they fit with the vision for Enso as a whole.
  4. Submit a Pull Request. Please give the PR a descriptive title (RFC: My Feature). The Pull Request will be open for feedback and discussion from the community and core team, and the author should be open to revising it in response to this feedback. The RFC will be assigned a shepherd from the core team who will be responsible for managing the RFC alongside the author.
  5. Evolve the RFC. Build consensus around the feature through your revisions. Feel free to reach out to the shepherd assigned to your proposal for discussion, as well as help identifying the key stakeholders and obstacles.
  6. The core team will participate in the discussion on the PR thread, and will summarise any offline discussion in the same thread.
  7. Once the RFC has reached a stable point, the shepherd will propose that the RFC enters the Final Comment Period (FCP), as well as a disposition for the RFC: Accept, Close or Postpone. It should be noted that taking this step does not require consensus, and should include a summary of the previous discussion and changes.
  8. The FCP lasts for 10 calendar days. This gives all stakeholders an ample chance to raise any final objections or comments before a decision is made. If substantial new arguments emerge during the FCP, the FCP may be cancelled.
  9. The RFC has a final decision reached, and is either Accepted (where it is merged into the repository after having an RFC number assigned to it), Postponed, where the PR is tagged and closed, or Rejected and closed.

Reviewing RFCs

While the RFC pull request is under discussion, the shepherd may organise meetings with the author and stakeholders to discuss the issue(s) in more detail. A summary from this meeting will be compiled by the shepherd and posted back to the pull request.

The RFC Life-Cycle

RFCs proceed through their life-cycle in this repository as follows:

  1. The Pull Request is submitted. The repository manager assigns appropriate labels to the RFC so that the relevant stakeholders can find it. It is also assigned a shepherd and tagged for discussion.
  2. Once discussion has stabilised, the RFC is proposed for the Final Comment Period, and tagged as such.
  3. At the end of the FCP, the RFC will be tagged with the decision made.
  4. If the RFC is accepted, it is then marked as Active and can be merged into this repository.
  5. Once merged, implementation can be commenced and pull requested.

Active RFCs

An RFC being ‘Active’ should not be viewed as a rubber stamp, and in particular it does not mean that the feature will be ultimately merged into Enso. It does mean that, in principle, stakeholders are in agreement on the feature and are amenable to it being merged.

Being accepted doesn’t mean that there is a priority assigned to its implementation, or a developer dedicated to implementing it. While it is not necessary (and in some cases not recommended) for the RFC author to write the implementation, it is likely to result in the RFC being seen to completion more swiftly than it otherwise would be.

Once accepted and active, small modifications to the RFC can be made via follow-on pull requests. While we usually intend for RFCs to reflect the final design, interim changes may necessitate small alterations to keep the RFC in sync with the final implementation.

Please note that the RFC should not be substantially changed at this point. If substantial changes are required, they should take place as a new RFC, linked to and from the old.

RFC Implementation

Some accepted RFCs are vital features that need to be implemented as soon as possible, while others can wait until a so-inclined developer comes along. Every accepted RFC is assigned a tracking issue in the Enso repository, and is then assigned a priority via the Enso repository triage process.

The author of an RFC is not obligated to implement it. Of course, the RFC author (like any other developer) is welcome to post an implementation for review after the RFC has been accepted.

If you are interested in working on the implementation for an “active” RFC, but cannot determine if someone else is already working on it, feel free to ask (e.g. by leaving a comment on the associated issue).

RFC Postponement

Some RFC pull requests are tagged with the ‘Postponed’ label when they are closed (as part of the rejection process). This label implies that we neither want to think about evaluating the proposal or implementing it until some time in the future. These pull requests may be re-opened when the time is right.

RFCs are usually postponed after some evaluation has taken place, and the label is usually given because the time is not right to consider or implement such a feature for now.


This repository and process takes significant inspiration from the Rust RFCs process, and the GHC Proposals process, so thank you to both communities for inspiring us!