Make caching on client side optional

.env.example

@@ -373,6 +373,10 @@ VITE_PUSHER_APP_CLUSTER="${PUSHER_APP_CLUSTER}"
 # cache_event_logging) become visible in the admin settings panel.
 # ENABLE_CACHING=false
 
+# When disabled, the front end reuses no stored API response (axios cache
+# and browser HTTP cache). Thumbnails stay cached.
+# CLIENT_CACHE_ENABLED=true
+
 ###################################################################
 # Payment integration (requires SE)                               #
 ###################################################################

app/View/Components/Meta.php

@@ -45,6 +45,7 @@ class Meta extends Component
 	public string $user_js_url;
 	public string $loading_indicator_mode;
 	public string $loading_indicator_url;
+	public bool $client_cache_enabled;
 	public int $width = 0;
 	public int $height = 0;
 
@@ -66,6 +67,8 @@ public function __construct()
 		$this->user_css_url = self::getUserCustomFiles('user.css');
 		$this->user_js_url = self::getUserCustomFiles('custom.js');
 		$this->setLoadingIndicator();
+		// Rendered into the page so the front end knows it before its first request.
+		$this->client_cache_enabled = config('features.client-cache') === true;
 
 		$base_url = url('/');
 		// Work around to try to satisfy everyone...

config/features.php

@@ -289,6 +289,19 @@
 	 */
 	'enable-caching' => (bool) env('ENABLE_CACHING', false),
 
+	/*
+	 |--------------------------------------------------------------------------
+	 | Client-side cache
+	 |--------------------------------------------------------------------------
+	 |
+	 | When disabled, the front end (v7 and v8) reuses no stored API
+	 | response: the axios response cache is skipped and requests keep asking
+	 | the browser not to answer from its HTTP cache. Thumbnails stay cached.
+	 | Enabled by default — set CLIENT_CACHE_ENABLED=false to always fetch
+	 | from the server.
+	 */
+	'client-cache' => (bool) env('CLIENT_CACHE_ENABLED', true),
+
 	/*
 	 |--------------------------------------------------------------------------
 	 | Enable Nuxt UI front-end (v8)

resources/js/config/axios-config.ts

@@ -1,8 +1,7 @@
 import axios, { AxiosError, InternalAxiosRequestConfig, type AxiosResponse } from "axios";
 import CSRF from "./csrf-getter";
-// import { setupCache } from "axios-cache-interceptor/dev";
-import { setupCache } from "axios-cache-interceptor";
 import InitService from "../services/init-service";
+import { isClientCacheEnabled, setUpClientCache } from "./client-cache";
 
 // Cached for the life of the session (unlike InitService.fetchMac()'s in-flight dedup, which only
 // coalesces concurrent callers of one fetch): once resolved, later Asset requests reuse this value
@@ -67,7 +66,7 @@ function needsMac(url: string | undefined): boolean {
 
 const AxiosConfig = {
 	axiosSetUp() {
-		setupCache(axios);
+		setUpClientCache(axios, isClientCacheEnabled());
 		axios.defaults.headers.common["X-Requested-With"] = "XMLHttpRequest";
 		axios.interceptors.request.use(
 			async function (config: InternalAxiosRequestConfig) {

resources/js/config/client-cache.test.ts

@@ -0,0 +1,87 @@
+/**
+ * SPDX-License-Identifier: MIT
+ * Copyright (c) 2017-2018 Tobias Reich
+ * Copyright (c) 2018-2026 LycheeOrg.
+ */
+
+// @vitest-environment jsdom
+import { describe, expect, it } from "vite-plus/test";
+import axios, { type AxiosAdapter, type InternalAxiosRequestConfig } from "axios";
+import type { AxiosCacheInstance } from "axios-cache-interceptor";
+import { parseClientCacheEnabled, setUpClientCache } from "@/config/client-cache";
+
+function metaTag(content: string): Element {
+	const meta = document.createElement("meta");
+	meta.setAttribute("name", "lychee-client-cache");
+	meta.setAttribute("content", content);
+	return meta;
+}
+
+// An instance whose requests never leave the test: every one is recorded and answered with a
+// response the cache would keep for an hour.
+function stubbedInstance(enabled: boolean): { instance: AxiosCacheInstance; sent: InternalAxiosRequestConfig[] } {
+	const sent: InternalAxiosRequestConfig[] = [];
+	const instance = axios.create();
+	instance.defaults.adapter = ((config: InternalAxiosRequestConfig) => {
+		sent.push(config);
+		return Promise.resolve({ data: "asset", status: 200, statusText: "OK", headers: { "cache-control": "private, max-age=3600" }, config });
+	}) as AxiosAdapter;
+	setUpClientCache(instance, enabled);
+	return { instance: instance as unknown as AxiosCacheInstance, sent };
+}
+
+describe("parseClientCacheEnabled()", () => {
+	it("is off when the tag says 0", () => {
+		expect(parseClientCacheEnabled(metaTag("0"))).toBe(false);
+	});
+
+	it("is on when the tag says 1", () => {
+		expect(parseClientCacheEnabled(metaTag("1"))).toBe(true);
+	});
+
+	it("is on without the tag", () => {
+		expect(parseClientCacheEnabled(null)).toBe(true);
+	});
+});
+
+describe("setUpClientCache()", () => {
+	it("answers a repeated request from its storage when on", async () => {
+		const { instance, sent } = stubbedInstance(true);
+
+		await instance.get("Asset/album/photo/small", { id: "asset" });
+		const second = await instance.get("Asset/album/photo/small", { id: "asset" });
+
+		expect(sent).toHaveLength(1);
+		expect(second.cached).toBe(true);
+	});
+
+	it("sends every request to the network with the no-cache headers when off", async () => {
+		const { instance, sent } = stubbedInstance(false);
+
+		await instance.get("Asset/album/photo/small", { id: "asset" });
+		await instance.get("Asset/album/photo/small", { id: "asset" });
+
+		expect(sent).toHaveLength(2);
+		for (const config of sent) {
+			expect(config.headers.get("Cache-Control")).toBe("no-cache, no-store, must-revalidate, max-age=0");
+			expect(config.headers.get("Pragma")).toBe("no-cache");
+			expect(config.headers.get("Expires")).toBe("0");
+		}
+	});
+
+	it("still answers a request that opts in from its storage when off", async () => {
+		const { instance, sent } = stubbedInstance(false);
+
+		await instance.get("Asset/album/photo/small", { id: "asset", cache: { enabled: true } });
+		const second = await instance.get("Asset/album/photo/small", { id: "asset", cache: { enabled: true } });
+
+		expect(sent).toHaveLength(1);
+		expect(second.cached).toBe(true);
+	});
+
+	it("keeps its storage when off, so cache clearing still works", () => {
+		const { instance } = stubbedInstance(false);
+
+		expect(() => instance.storage.remove("asset")).not.toThrow();
+	});
+});

resources/js/config/client-cache.ts

@@ -0,0 +1,46 @@
+/**
+ * SPDX-License-Identifier: MIT
+ * Copyright (c) 2017-2018 Tobias Reich
+ * Copyright (c) 2018-2026 LycheeOrg.
+ */
+
+import type { AxiosInstance, InternalAxiosRequestConfig } from "axios";
+import { setupCache } from "axios-cache-interceptor";
+
+/**
+ * Client-side cache switch chosen by the server.
+ *
+ * `Meta` renders `<meta name="lychee-client-cache" content="0|1">` from `CLIENT_CACHE_ENABLED`,
+ * so the value is known before the first request. The tag is read once and cached; only
+ * `content="0"` turns the cache off, a missing tag means on (the flag's default).
+ */
+let cached: boolean | undefined = undefined;
+
+export function parseClientCacheEnabled(meta: Element | null): boolean {
+	return meta?.getAttribute("content") !== "0";
+}
+
+export function isClientCacheEnabled(): boolean {
+	cached ??= parseClientCacheEnabled(document.querySelector('meta[name="lychee-client-cache"]'));
+	return cached;
+}
+
+// The headers axios-cache-interceptor's `cacheTakeover` adds to every request when enabled: they
+// keep the browser HTTP cache from answering, which a disabled interceptor no longer does.
+function addNoCacheHeaders(config: InternalAxiosRequestConfig): InternalAxiosRequestConfig {
+	config.headers.set("Cache-Control", "no-cache, no-store, must-revalidate, max-age=0", false);
+	config.headers.set("Pragma", "no-cache", false);
+	config.headers.set("Expires", "0", false);
+	return config;
+}
+
+/**
+ * Installs the response cache on `instance`. Disabled, it stores and serves nothing but keeps its
+ * storage, so `clearCache()` callers still work (they just remove nothing).
+ */
+export function setUpClientCache(instance: AxiosInstance, enabled: boolean): void {
+	setupCache(instance, { enabled: enabled });
+	if (!enabled) {
+		instance.interceptors.request.use(addNoCacheHeaders);
+	}
+}

resources/js/services/thumb-asset-service.test.ts

@@ -78,3 +78,10 @@ describe("ThumbAssetService.clear() (S-102-15)", () => {
 		expect(signal.aborted).toBe(true);
 	});
 });
+
+describe("ThumbAssetService.acquire()", () => {
+	it("keeps the axios response cache whatever CLIENT_CACHE_ENABLED says", () => {
+		ThumbAssetService.acquire("album", "p5", "small").release();
+		expect(get.mock.calls[0][1]).toMatchObject({ cache: { enabled: true } });
+	});
+});

resources/js/services/thumb-asset-service.ts

@@ -1,4 +1,4 @@
-import axios from "axios";
+import axios, { type AxiosRequestConfig } from "axios";
 import Constants from "./constants";
 
 type CacheEntry = {
@@ -95,7 +95,9 @@ const ThumbAssetService = {
 					responseType: "blob",
 					signal: controller.signal,
 					data: {},
-				})
+					// Thumbnails stay cached even with CLIENT_CACHE_ENABLED=false.
+					cache: { enabled: true },
+				} as AxiosRequestConfig)
 				.then((response) => {
 					if (entry !== undefined) {
 						entry.settled = true;

resources/views/components/meta.blade.php

@@ -5,6 +5,7 @@
 <meta name="mobile-web-app-status-bar-style" content="black">
 <meta name="mobile-web-app-capable" content="yes">
 <meta name="lychee-loading-indicator" content="{{ $loading_indicator_mode }}" data-url="{{ $loading_indicator_url }}">
+<meta name="lychee-client-cache" content="{{ $client_cache_enabled ? '1' : '0' }}">
 @if(Features::inactive('white_label_enabled'))
 <meta name="generator" content="Lychee v7">
 @endif

tests/Feature_v3/ClientCache/ClientCacheMetaTest.php

@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * SPDX-License-Identifier: MIT
+ * Copyright (c) 2017-2018 Tobias Reich
+ * Copyright (c) 2018-2026 LycheeOrg.
+ */
+
+/**
+ * We don't care for unhandled exceptions in tests.
+ * It is the nature of a test to throw an exception.
+ * Without this suppression we had 100+ Linter warning in this file which
+ * don't help anything.
+ *
+ * @noinspection PhpDocMissingThrowsInspection
+ * @noinspection PhpUnhandledExceptionInspection
+ */
+
+namespace Tests\Feature_v3\ClientCache;
+
+use Tests\Feature_v3\Base\BaseApiWithDataTest;
+
+/**
+ * The client cache flag is rendered into the HTML page.
+ */
+class ClientCacheMetaTest extends BaseApiWithDataTest
+{
+	public function tearDown(): void
+	{
+		config(['features.client-cache' => true]);
+		parent::tearDown();
+	}
+
+	public function testEnabledByDefault(): void
+	{
+		$this->assertMetaTag('1');
+	}
+
+	public function testDisabled(): void
+	{
+		config(['features.client-cache' => false]);
+
+		$this->assertMetaTag('0');
+	}
+
+	private function assertMetaTag(string $content): void
+	{
+		$response = $this->get('/gallery');
+
+		$this->assertOk($response);
+		$response->assertSee('<meta name="lychee-client-cache" content="' . $content . '">', false);
+	}
+}