feat(frontend): check if exchange enabled for initialization (#3363)

# Motivation

The derived store `exchangeInitialized` should be considered `true` when
the exchange is disabled. This mainly happens for test environments
(like E2E) where we don't provide API keys and we forcibly turn off the
exchanges via env variable `VITE_EXCHANGE_DISABLED`: it is mostly used
for loading states, so just for visual changes.

# Changes

- Extract parsed env variable `EXCHANGE_DISABLED` and export it
globally.
- Include it in the logic of `exchangeInitialized`: it is true if either
`exchangeInitialized` data is non-nullish or if exchange is disabled.

# Tests

Created some tests for the derived.

---------

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

src/frontend/src/env/exchange.env.ts

@@ -0,0 +1,2 @@
+export const EXCHANGE_DISABLED =
+	JSON.parse(import.meta.env.VITE_EXCHANGE_DISABLED ?? false) === true;

src/frontend/src/lib/components/exchange/ExchangeWorker.svelte

@@ -1,14 +1,13 @@
 <script lang="ts">
 	import { debounce } from '@dfinity/utils';
 	import { onDestroy, onMount } from 'svelte';
+	import { EXCHANGE_DISABLED } from '$env/exchange.env';
 	import { enabledIcrcLedgerCanisterIdsNoCk } from '$icp/derived/icrc.derived';
 	import { enabledMergedErc20TokensAddresses } from '$icp-eth/derived/icrc-erc20.derived';
 	import { type ExchangeWorker, initExchangeWorker } from '$lib/services/worker.exchange.services';
 
 	let worker: ExchangeWorker | undefined;
 
-	const EXCHANGE_DISABLED = JSON.parse(import.meta.env.VITE_EXCHANGE_DISABLED ?? false) === true;
-
 	onMount(async () => {
 		if (EXCHANGE_DISABLED) {
 			// Using the exchange API during development if not necessary and given its limitation of calls per minute is annoying at it often throws errors on server reload.

src/frontend/src/lib/derived/exchange.derived.ts

@@ -1,3 +1,4 @@
+import { EXCHANGE_DISABLED } from '$env/exchange.env';
 import {
 	BTC_MAINNET_TOKEN_ID,
 	BTC_REGTEST_TOKEN_ID,
@@ -13,10 +14,12 @@ import type { ExchangesData } from '$lib/types/exchange';
 import { nonNullish } from '@dfinity/utils';
 import { derived, type Readable } from 'svelte/store';
 
-export const exchangeInitialized: Readable<boolean> = derived([exchangeStore], ([$exchangeStore]) =>
-	nonNullish($exchangeStore)
+export const exchangeInitialized: Readable<boolean> = derived(
+	[exchangeStore],
+	([$exchangeStore]) => EXCHANGE_DISABLED || nonNullish($exchangeStore)
 );
 
+// TODO: create tests for store
 export const exchanges: Readable<ExchangesData> = derived(
 	[exchangeStore, enabledErc20Tokens, enabledIcrcTokens],
 	([$exchangeStore, $erc20Tokens, $icrcTokens]) => {

src/frontend/src/tests/lib/derived/exchange.derived.spec.ts

@@ -0,0 +1,36 @@
+import * as exchangeEnv from '$env/exchange.env';
+import { exchangeInitialized } from '$lib/derived/exchange.derived';
+import { exchangeStore } from '$lib/stores/exchange.store';
+import { get } from 'svelte/store';
+import { expect } from 'vitest';
+
+describe('exchange.derived', () => {
+	describe('exchangeInitialized', () => {
+		beforeEach(() => {
+			vi.spyOn(exchangeEnv, 'EXCHANGE_DISABLED', 'get').mockImplementation(() => false);
+		});
+
+		it('should return false when exchange store is empty', () => {
+			expect(get(exchangeInitialized)).toBe(false);
+		});
+
+		it('should return true when exchange is disabled', () => {
+			vi.spyOn(exchangeEnv, 'EXCHANGE_DISABLED', 'get').mockImplementationOnce(() => true);
+
+			expect(get(exchangeInitialized)).toBe(true);
+		});
+
+		it('should return true when exchange store is not empty', () => {
+			exchangeStore.set([{ ethereum: { usd: 1 } }]);
+
+			expect(get(exchangeInitialized)).toBe(true);
+		});
+
+		it('should return false when exchange store is reset', () => {
+			exchangeStore.set([{ ethereum: { usd: 1 } }]);
+			exchangeStore.reset();
+
+			expect(get(exchangeInitialized)).toBe(false);
+		});
+	});
+});