From bb44a7d7789a518c291c194d697b80e90b9f3a31 Mon Sep 17 00:00:00 2001
From: Justin Ribeiro <justin@justinribeiro.com>
Date: Mon, 13 Aug 2018 22:48:21 -0700
Subject: [PATCH] core(uses-long-cache-ttl): handle multiple cache-control
 headers (#5745)

---
 .../byte-efficiency/uses-long-cache-ttl.js    |  8 +++++++-
 .../uses-long-cache-ttl-test.js               | 19 +++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/lighthouse-core/audits/byte-efficiency/uses-long-cache-ttl.js b/lighthouse-core/audits/byte-efficiency/uses-long-cache-ttl.js
index 32462e039c24..bbea54ac7c17 100644
--- a/lighthouse-core/audits/byte-efficiency/uses-long-cache-ttl.js
+++ b/lighthouse-core/audits/byte-efficiency/uses-long-cache-ttl.js
@@ -185,7 +185,13 @@ class CacheHeaders extends Audit {
         /** @type {Map<string, string>} */
         const headers = new Map();
         for (const header of record.responseHeaders || []) {
-          headers.set(header.name.toLowerCase(), header.value);
+          if (headers.has(header.name.toLowerCase())) {
+            const previousHeaderValue = headers.get(header.name.toLowerCase());
+            headers.set(header.name.toLowerCase(),
+              `${previousHeaderValue}, ${header.value}`);
+          } else {
+            headers.set(header.name.toLowerCase(), header.value);
+          }
         }
 
         const cacheControl = parseCacheControl(headers.get('cache-control'));
diff --git a/lighthouse-core/test/audits/byte-efficiency/uses-long-cache-ttl-test.js b/lighthouse-core/test/audits/byte-efficiency/uses-long-cache-ttl-test.js
index 148fa6df213f..d49bae881c1b 100644
--- a/lighthouse-core/test/audits/byte-efficiency/uses-long-cache-ttl-test.js
+++ b/lighthouse-core/test/audits/byte-efficiency/uses-long-cache-ttl-test.js
@@ -119,6 +119,25 @@ describe('Cache headers audit', () => {
     });
   });
 
+  it('respects multiple cache-control headers', () => {
+    networkRecords = [
+      networkRecord({headers: {
+        'cache-control': 'max-age=31536000, public',
+        'Cache-control': 'no-transform',
+      }}),
+      networkRecord({headers: {
+        'Cache-Control': 'no-transform',
+        'cache-control': 'max-age=3600',
+        'Cache-control': 'public',
+      }}),
+    ];
+
+    return CacheHeadersAudit.audit(artifacts, {options}).then(result => {
+      const items = result.extendedInfo.value.results;
+      assert.equal(items.length, 1);
+    });
+  });
+
   it('catches records with Etags', () => {
     networkRecords = [
       networkRecord({headers: {etag: 'md5hashhere'}}),