feature-flags

Feature Flags

Feature flags gate experimental functionality behind user-configurable settings, enabling safe rollout (default off), user opt-in, and easy rollback.

Checking Feature State

import "github.com/marcus/sidecar/internal/features"

if features.IsEnabled("tmux_interactive_input") {
    // Feature-gated code
}

Adding a New Feature Flag

1. Define the feature in internal/features/features.go:

var MyNewFeature = Feature{
    Name:        "my_new_feature",
    Default:     false,
    Description: "Description of what this enables",
}

1. Add to the allFeatures slice:

var allFeatures = []Feature{
    TmuxInteractiveInput,
    MyNewFeature, // Add here
}

1. Use the feature check in your code:

if features.IsEnabled("my_new_feature") {
    // New functionality
}

That is all a flag needs to be reachable. Configuration → System → Feature Flags derives its list from features.ListAll(), so registering a feature puts a working switch on the page with the registry's own Name as the label and Description as the help text. There is no second list to remember.

Giving a flag better copy (optional)

previewCopy in internal/configui/page_flags.go overrides the registry's wording per flag. Only fill in what you want to change:

features.MyNewFeature.Name: {
    label:   "Human-readable name",
    help:    "One sentence on what turning this on does.",
    restart: true, // only if a consumer reads it once at startup
    note:    "An honest scope line for a flag that applies live but not retroactively.",
},

restart must be checked against what actually consumes the flag, never added as blanket caution — a flag read at the point of use applies immediately and must not claim otherwise. Both restart and note render when both are set.

A flag that another page already owns as a first-class setting sets owner and ownerControl instead. It is then listed read-only with a jump to the control that owns it, because two switches over one value is how surfaces start disagreeing. If the owning page's control means more than the raw flag — Panels' Conversations switch is the flag and the plugin's own enabled key — also set reads so the row reports the owner's answer rather than the flag's.