From 1df4bff2998d1103b22543abb697637526e218fd Mon Sep 17 00:00:00 2001
From: Joey Parrish <joeyparrish@google.com>
Date: Wed, 2 Nov 2022 17:55:47 -0700
Subject: [PATCH 1/3] fix: Fix HLS lazy-loading exception during update

If a stream switch occurs during a playlist update, that update may
need to be cancelled.  This handles this edge case to prevent an
exception trying to access stream.segmentIndex.

Closes #4647
---
 lib/hls/hls_parser.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/hls/hls_parser.js b/lib/hls/hls_parser.js
index f2e8166681..83fe98fd6a 100644
--- a/lib/hls/hls_parser.js
+++ b/lib/hls/hls_parser.js
@@ -347,6 +347,10 @@ shaka.hls.HlsParser = class {
       uriObj.setQueryData(new goog.Uri.QueryData('_HLS_skip=YES'));
     }
     const response = await this.requestManifest_(uriObj.toString());
+    if (!streamInfo.stream.segmentIndex) {
+      // The stream was closed since the update was first requested.
+      return;
+    }
 
     /** @type {shaka.hls.Playlist} */
     const playlist = this.manifestTextParser_.parsePlaylist(

From bdaa88a1da6b8b42262e7c31f820184bb69c83eb Mon Sep 17 00:00:00 2001
From: Joey Parrish <joeyparrish@google.com>
Date: Thu, 3 Nov 2022 19:02:51 -0700
Subject: [PATCH 2/3] New test case

---
 test/hls/hls_live_unit.js | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/test/hls/hls_live_unit.js b/test/hls/hls_live_unit.js
index 18ab0919ed..319b3bb3ad 100644
--- a/test/hls/hls_live_unit.js
+++ b/test/hls/hls_live_unit.js
@@ -736,6 +736,54 @@ describe('HlsParser live', () => {
             manifest.variants[1].video, [ref4]);
       });
 
+      it('handles switching during update', async () => {
+        const ref1 = makeReference(
+            'test:/main.mp4', 0, 2, /* syncTime= */ null);
+        const ref2 = makeReference(
+            'test:/main2.mp4', 2, 4, /* syncTime= */ null);
+        const ref4 = makeReference(
+            'test:/main4.mp4', 2, 4, /* syncTime= */ null);
+
+        const secondVariant = [
+          '#EXT-X-STREAM-INF:BANDWIDTH=300,CODECS="avc1",',
+          'RESOLUTION=1200x940,FRAME-RATE=60\n',
+          'video2',
+        ].join('');
+        const masterWithTwoVariants = master + secondVariant;
+        configureNetEngineForInitialManifest(masterWithTwoVariants,
+            mediaWithAdditionalSegment, mediaWithAdditionalSegment2);
+
+        const manifest = await parser.start('test:/master', playerInterface);
+        await manifest.variants[0].video.createSegmentIndex();
+        ManifestParser.verifySegmentIndex(
+            manifest.variants[0].video, [ref1, ref2]);
+        expect(manifest.variants[1].video.segmentIndex).toBe(null);
+
+        // Update.
+        fakeNetEngine
+            .setResponseText('test:/video', mediaWithRemovedSegment)
+            .setResponseText('test:/video2', mediaWithRemovedSegment2);
+
+        const updatePromise = parser.update();
+
+        // Verify that the update is not yet complete.
+        expect(manifest.variants[0].video.segmentIndex).not.toBe(null);
+        ManifestParser.verifySegmentIndex(
+            manifest.variants[0].video, [ref1, ref2]);
+
+        // Mid-update, switch.
+        await manifest.variants[0].video.closeSegmentIndex();
+        await manifest.variants[1].video.createSegmentIndex();
+
+        // Finish the update.
+        await updatePromise;
+
+        // Check for variants to be as expected.
+        expect(manifest.variants[0].video.segmentIndex).toBe(null);
+        ManifestParser.verifySegmentIndex(
+            manifest.variants[1].video, [ref4]);
+      });
+
       it('handles updates with redirects', async () => {
         const oldRef1 = makeReference(
             'test:/main.mp4', 0, 2, /* syncTime= */ null);

From 5078c179d94a150e457507b1a6a5a8681d4dbecd Mon Sep 17 00:00:00 2001
From: Joey Parrish <joeyparrish@google.com>
Date: Thu, 3 Nov 2022 19:03:00 -0700
Subject: [PATCH 3/3] Additional fix for issue exposed by test case

---
 lib/hls/hls_parser.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/hls/hls_parser.js b/lib/hls/hls_parser.js
index 83fe98fd6a..008ada5af2 100644
--- a/lib/hls/hls_parser.js
+++ b/lib/hls/hls_parser.js
@@ -1687,6 +1687,10 @@ shaka.hls.HlsParser = class {
   notifySegmentsForStreams_(streams) {
     const references = [];
     for (const stream of streams) {
+      if (!stream.segmentIndex) {
+        // The stream was closed since the list of streams was built.
+        continue;
+      }
       stream.segmentIndex.forEachTopLevelReference((reference) => {
         references.push(reference);
       });