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Environments

Dev / Staging / Prod environments, selectable per build and switchable at runtime (a current selection plus a next pending one, restart to apply). Two cooperating halves.

1. Build default (app.config.ts + expo-constants)

Which environment a build defaults to is chosen by the APP_ENV build variable, baked into app.config.ts's extra and read at runtime through expo-constants — set at build time:

APP_ENV=staging npx expo prebuild   # use cross-env on Windows, or a CI variable

getBuildDefaultEnvironment() is the single place this value is read; it falls back to development if unset.

2. Runtime switching (EnvironmentService)

EnvironmentService exposes the active environment and its config, and persists a runtime override via KeyValueStore (MMKV). Features consume this service, never app.config.ts directly (convention).

const { environment } = useServices();
const { apiBaseUrl } = environment.getConfig(); // per-env values

Per-environment values live in a typed map, environments.ts — type-safe rather than .env.* files:

Value development staging production
logging.console on off off
logging.file on on on
logging.minimumLevel debug info warn
diagnosticsEnabled on on off
crashReportingEnabled on on off
remoteConfig.fetchIntervalMinutes 1 1 720

crashReportingEnabled gates Bugsee to internal builds — off in production, which is billed per user (CrashReporting.md). remoteConfig.fetchIntervalMinutes tunes the Firebase fetch cadence (FirebaseRemoteConfig.md). (apiBaseUrl and appStoreUrl are also per-env; the sample points apiBaseUrl at the public Dad Jokes API in every environment, and appStoreUrl at placeholder store URLs.)

Switching semantics (restart to apply)

  • setEnvironment(env) persists the override and pushes it onto pending$. The active environment and the wired services graph do not change mid-session.
  • The composition root reads the persisted override once at startup and wires the whole graph (HTTP base URL, logging levels, …) from that config.
  • Applying a switch therefore requires an app restart. The diagnostics environment picker shows a "restart to apply" banner whenever pending$ differs from the current environment.
  • reset() deletes the override; the next launch reverts to the build default.

Live re-wiring on switch is deliberately avoided — applying a switch defers to a restart because the environment feeds construction-time dependencies.

Testing

DefaultEnvironmentService takes a KeyValueStore and the build default by constructor, so Tier-1 tests drive it with an InMemoryKeyValueStore and an explicit default — no expo-constants, no native modules (test). MockEnvironmentService is a no-persistence fake for consumers that just need a fixed environment.