🐛 fix for PERCY_GZIP flag (#1842)

* :bug fix for gzip * :bug fix for gzip * test fix * test fix
percy · Jan 10, 2025 · 20b4d94 · 20b4d94
1 parent 4d589ce
commit 20b4d94
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Showing 3 changed files with 67 additions and 4 deletions.
diff --git a/packages/core/src/discovery.js b/packages/core/src/discovery.js
@@ -12,7 +12,8 @@ import {
   snapshotLogName,
   waitForTimeout,
   withRetries,
-  waitForSelectorInsideBrowser
+  waitForSelectorInsideBrowser,
+  isGzipped
 } from './utils.js';
 import {
   sha256hash
@@ -213,8 +214,12 @@ function processSnapshotResources({ domSnapshot, resources, ...snapshot }) {
 
   if (process.env.PERCY_GZIP) {
     for (let index = 0; index < resources.length; index++) {
-      resources[index].content = Pako.gzip(resources[index].content);
-      resources[index].sha = sha256hash(resources[index].content);
+      const alreadyZipped = isGzipped(resources[index].content);
+      /* istanbul ignore next: very hard to mock true */
+      if (!alreadyZipped) {
+        resources[index].content = Pako.gzip(resources[index].content);
+        resources[index].sha = sha256hash(resources[index].content);
+      }
     }
   }
 

diff --git a/packages/core/src/utils.js b/packages/core/src/utils.js
@@ -384,6 +384,21 @@ export function base64encode(content) {
     .toString('base64');
 }
 
+// It checks if content is already gzipped or not.
+// We don't want to gzip already gzipped content.
+export function isGzipped(content) {
+  if (!(content instanceof Uint8Array || content instanceof ArrayBuffer)) {
+    return false;
+  }
+
+  // Ensure content is a Uint8Array
+  const data =
+    content instanceof ArrayBuffer ? new Uint8Array(content) : content;
+
+  // Gzip magic number: 0x1f8b
+  return data.length > 2 && data[0] === 0x1f && data[1] === 0x8b;
+}
+
 const RESERVED_CHARACTERS = {
   '%3A': ':',
   '%23': '#',

diff --git a/packages/core/test/utils.test.js b/packages/core/test/utils.test.js
@@ -1,7 +1,8 @@
-import { decodeAndEncodeURLWithLogging, waitForSelectorInsideBrowser, compareObjectTypes } from '../src/utils.js';
+import { decodeAndEncodeURLWithLogging, waitForSelectorInsideBrowser, compareObjectTypes, isGzipped } from '../src/utils.js';
 import { logger, setupTest } from './helpers/index.js';
 import percyLogger from '@percy/logger';
 import Percy from '@percy/core';
+import Pako from 'pako';
 
 describe('utils', () => {
   let log;
@@ -179,4 +180,46 @@ describe('utils', () => {
       });
     });
   });
+  describe('isGzipped', () => {
+    it('returns true for gzipped content', () => {
+      const compressed = Pako.gzip('Hello, world!');
+      expect(isGzipped(compressed)).toBe(true);
+    });
+
+    it('returns false for plain uncompressed content', () => {
+      const uncompressed = new TextEncoder().encode('Hello, world!');
+      expect(isGzipped(uncompressed)).toBe(false);
+    });
+
+    it('returns false for a plain string input', () => {
+      const invalidInput = 'Not a Uint8Array';
+      expect(isGzipped(invalidInput)).toBe(false);
+    });
+
+    it('returns false for an empty Uint8Array', () => {
+      const emptyArray = new Uint8Array([]);
+      expect(isGzipped(emptyArray)).toBe(false);
+    });
+
+    it('returns false for an undefined', () => {
+      const empty = undefined;
+      expect(isGzipped(empty)).toBe(false);
+    });
+
+    it('returns false for an ArrayBuffer without Gzip magic number', () => {
+      const buffer = new ArrayBuffer(10);
+      const view = new Uint8Array(buffer);
+      view[0] = 0x00;
+      view[1] = 0x01;
+      expect(isGzipped(buffer)).toBe(false);
+    });
+
+    it('returns true for an ArrayBuffer with Gzip magic number', () => {
+      const buffer = new ArrayBuffer(10);
+      const view = new Uint8Array(buffer);
+      view[0] = 0x1f; // Gzip magic number
+      view[1] = 0x8b; // Gzip magic number
+      expect(isGzipped(buffer)).toBe(true);
+    });
+  });
 });