flag-prune

Recipes

These examples are provider-agnostic. Replace the selectors and paths with the exact shapes used in your codebase.

For Unleash, LaunchDarkly, PostHog, Statsig, and OpenFeature commands, see the feature flag provider guides.

Remove a hook flag

Source:

const enabled = useFlag("new-checkout");

return enabled ? <NewCheckout /> : <CurrentCheckout />

Command:

npx flag-prune --set 'useFlag("new-checkout")=false' --write src

Result:

return <CurrentCheckout />

Remove a client method flag

Source:

if (client.isEnabled("new-checkout", loadContext())) {
  startNewCheckout()
} else {
  startCurrentCheckout()
}

Command:

npx flag-prune \
  --set 'client.isEnabled("new-checkout")=true' \
  --write \
  src

Result:

loadContext()
startNewCheckout()

The required loadContext() evaluation remains even though its result is no longer needed.

Remove an imported constant

Source:

import { NEW_CHECKOUT as enabled, metadata } from "./flags";

if (enabled) {
  startNewCheckout()
} else {
  startCurrentCheckout()
}

metadata()

Command:

npx flag-prune --set './flags#NEW_CHECKOUT=false' --write src

Result:

import { metadata } from "./flags"

startCurrentCheckout()
metadata()

If the configured binding is the final import specifier, flag-prune leaves a side-effect import by default:

import "./flags"

Only use --remove-side-effect-imports when the module is proven side-effect-free.

Resolve a string variant

Source:

const variant = getVariant("checkout")

if (variant === "treatment") {
  showTreatment()
} else {
  showControl()
}

Command:

npx flag-prune \
  --set 'getVariant("checkout")=treatment' \
  --write \
  src

Result:

showTreatment()

Resolve a variant object

Some SDKs return a variant object rather than a bare string. Give the flag its final object value and flag-prune folds each static member read.

Source:

const variant = getVariant("checkout")

if (variant.enabled && variant.name === "treatment") {
  showTreatment()
} else {
  showControl()
}

Command:

npx flag-prune \
  --set 'getVariant("checkout")={ enabled: true, name: "treatment" }' \
  --write \
  src

Result:

showTreatment()

If the object is also used as a whole value, the declaration is kept and only the member reads are folded:

const variant = { enabled: true, name: "treatment" }
track(variant)
showTreatment()

Remove a conditional object spread

A flag inside an object spread often folds to a value that spreads nothing.

Source:

const content = {
  state: null,
  ...(flagValue ? {} : { permission: 1 }),
}

Command:

npx flag-prune --set 'flagValue=true' --write src

Result:

const content = {
  state: null,
}

The ...({}) spread is removed because it contributes no properties. See Empty object spreads are removed for the exact rules.

Resolve a numeric limit

Source:

if (limits.maxSeats >= 10) {
  showEnterpriseControls()
} else {
  showStarterControls()
}

Command:

npx flag-prune --set 'limits.maxSeats=25' --write src

Result:

showEnterpriseControls()

Resolve a nullable override

Source:

const theme = readThemeOverride() ?? defaultTheme

Command:

npx flag-prune --set 'readThemeOverride()=null' --write src

Result:

const theme = defaultTheme

Remove several flags in one migration

npx flag-prune \
  --set 'useFlag("new-checkout")=false' \
  --set 'getVariant("checkout-copy")=control' \
  --set './flags#SHOW_CHECKOUT_BADGE=false' \
  --write \
  src

Related rules are simplified together, which can remove branches that depend on combinations such as A && B.

Preview a pull-request migration

npx flag-prune \
  --set 'useFlag("new-checkout")=false' \
  --diff \
  src

Dry-run and diff output are already the defaults, but spelling them out can make a saved migration command easier to understand.

Check that cleanup has been applied

npx flag-prune \
  --set 'useFlag("new-checkout")=false' \
  --check \
  --no-diff \
  src

Exit code 1 means files would change. This is useful while a cleanup branch is being prepared or when enforcing a known final value in CI.

Produce JSON for an agent or script

npx flag-prune \
  --set 'useFlag("new-checkout")=false' \
  --json \
  src > flag-prune-report.json

The JSON includes an aggregate report and a per-file report.

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