From e8e5cf86fba90f36735372006fad12f8ea4c9b69 Mon Sep 17 00:00:00 2001
From: Ophelia Goldstein <159258143+opheliagoldstein@users.noreply.github.com>
Date: Wed, 8 Oct 2025 01:19:54 +0300
Subject: [PATCH] feat: disable cache with proper headers when CACHE_SECONDS
 env is zero (#4539)

* feat: disable cache with proper headers when CACHE_SECONDS env is zero

* Update src/common/cache.js

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Alexandr <qwerty541zxc@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/common/cache.js | 37 ++++++++++++++++++++++++++++++++++---
 tests/api.test.js   | 38 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/src/common/cache.js b/src/common/cache.js
index c39a4b5d..a4e68113 100644
--- a/src/common/cache.js
+++ b/src/common/cache.js
@@ -15,13 +15,31 @@ import { clampValue, CONSTANTS } from "./utils.js";
 const resolveCacheSeconds = ({ requested, def, min, max }) => {
   let cacheSeconds = clampValue(isNaN(requested) ? def : requested, min, max);
 
-  cacheSeconds = process.env.CACHE_SECONDS
-    ? parseInt(process.env.CACHE_SECONDS, 10) || cacheSeconds
-    : cacheSeconds;
+  if (process.env.CACHE_SECONDS) {
+    const envCacheSeconds = parseInt(process.env.CACHE_SECONDS, 10);
+    if (!isNaN(envCacheSeconds)) {
+      cacheSeconds = envCacheSeconds;
+    }
+  }
 
   return cacheSeconds;
 };
 
+/**
+ * Disables caching by setting appropriate headers on the response object.
+ *
+ * @param {Object} res The response object.
+ */
+const disableCaching = (res) => {
+  // Disable caching for browsers, shared caches/CDNs, and GitHub Camo.
+  res.setHeader(
+    "Cache-Control",
+    "no-cache, no-store, must-revalidate, max-age=0, s-maxage=0",
+  );
+  res.setHeader("Pragma", "no-cache");
+  res.setHeader("Expires", "0");
+};
+
 /**
  * Sets the Cache-Control headers on the response object.
  *
@@ -29,6 +47,11 @@ const resolveCacheSeconds = ({ requested, def, min, max }) => {
  * @param {number} cacheSeconds The cache seconds to set in the headers.
  */
 const setCacheHeaders = (res, cacheSeconds) => {
+  if (cacheSeconds < 1) {
+    disableCaching(res);
+    return;
+  }
+
   res.setHeader(
     "Cache-Control",
     `max-age=${cacheSeconds}, ` +
@@ -43,6 +66,14 @@ const setCacheHeaders = (res, cacheSeconds) => {
  * @param {Object} res The response object.
  */
 const setErrorCacheHeaders = (res) => {
+  const envCacheSeconds = process.env.CACHE_SECONDS
+    ? parseInt(process.env.CACHE_SECONDS, 10)
+    : NaN;
+  if (!isNaN(envCacheSeconds) && envCacheSeconds < 1) {
+    disableCaching(res);
+    return;
+  }
+
   // Use lower cache period for errors.
   res.setHeader(
     "Cache-Control",
diff --git a/tests/api.test.js b/tests/api.test.js
index 2b4f83c9..bd255455 100644
--- a/tests/api.test.js
+++ b/tests/api.test.js
@@ -1,6 +1,6 @@
 // @ts-check
 
-import { jest } from "@jest/globals";
+import { beforeEach, jest } from "@jest/globals";
 import axios from "axios";
 import MockAdapter from "axios-mock-adapter";
 import api from "../api/index.js";
@@ -99,6 +99,10 @@ const faker = (query, data) => {
   return { req, res };
 };
 
+beforeEach(() => {
+  process.env.CACHE_SECONDS = undefined;
+});
+
 afterEach(() => {
   mock.reset();
 });
@@ -224,6 +228,38 @@ describe("Test /api/", () => {
     ]);
   });
 
+  it("should properly set cache using CACHE_SECONDS env variable", async () => {
+    process.env.CACHE_SECONDS = "10000";
+
+    const { req, res } = faker({}, data_stats);
+    await api(req, res);
+
+    expect(res.setHeader.mock.calls).toEqual([
+      ["Content-Type", "image/svg+xml"],
+      [
+        "Cache-Control",
+        `max-age=10000, s-maxage=10000, stale-while-revalidate=${CONSTANTS.ONE_DAY}`,
+      ],
+    ]);
+  });
+
+  it("should disable cache when CACHE_SECONDS is set to 0", async () => {
+    process.env.CACHE_SECONDS = "0";
+
+    const { req, res } = faker({}, data_stats);
+    await api(req, res);
+
+    expect(res.setHeader.mock.calls).toEqual([
+      ["Content-Type", "image/svg+xml"],
+      [
+        "Cache-Control",
+        "no-cache, no-store, must-revalidate, max-age=0, s-maxage=0",
+      ],
+      ["Pragma", "no-cache"],
+      ["Expires", "0"],
+    ]);
+  });
+
   it("should set proper cache with clamped values", async () => {
     {
       let { req, res } = faker({ cache_seconds: 200_000 }, data_stats);