Feature Flagging

To ensure Desktop along without being blocked on design feedback, we need a way to be able to ship features that are stable but not necessarily ready for general usage. This document outlines what we should flag and how to flag these features.

What Should Be Feature Flagged?

A preview feature can be considered as:

• something that has a well-defined scope
• a consensus exists that the team is happy to proceed, but
• some details need to be thought through or clarified

We're currently focused on user interface changes - new views, significant changes to existing views, and so on. We can revisit this list when we identify other cases where this sort of feature flagging needs to occur.

A beta feature should be:

• a feature that is slated for an upcoming release, and
• is usably complete, but
• needs more testing, or
• needs to be used to see how it feels

Beta features are a superset of preview features.

Why not just ship it?

A few reasons:

• some solutions just need time to appear, and this lets us get working code out quicker.
• we want to get feedback easily - users can opt-in to these preview features.
• we want to be conservative with evolving the UI - most users aren't fans of frequent, unnecessary churn.
• if we don't like something we can pull it before people get too attached to it.

How to Feature Flag?

First add a new function to feature-flag.ts. The function should usually check enableDevelopmentFeatures() or enableBetaFeatures(). Then, at runtime, your code should check your feature flag function and either display the new feature or the existing one.

See pull request integration in #3339 for an example.

This separation and naming scheme makes it easier to clean up the new or old feature once things are stabilized.

How to test

Opting-in for preview features

1. Set the GITHUB_DESKTOP_PREVIEW_FEATURES environment variable to 1
2. Restart GitHub Desktop

Don't have that environment variable? No worries, simply create it. (here's a handy guide for doing that on most major OSs).

Opting-out for preview features

1. Remove the GITHUB_DESKTOP_PREVIEW_FEATURES environment variable
2. Restart GitHub Desktop