fix: Allow EXT-X-PART with no segment

Author: kuu

stringify.ts

@@ -363,8 +363,10 @@ function buildSegment(lines: LineArray, segment: Segment, lastKey: string, lastM
   if (hint) {
     return [lastKey, lastMap];
   }
-  const duration = version < 3 ? Math.round(segment.duration) : buildDecimalFloatingNumber(segment.duration, getNumberOfDecimalPlaces(segment.duration));
-  lines.push(`#EXTINF:${duration},${unescape(encodeURIComponent(segment.title || ''))}`);
+  if (typeof segment.duration === 'number' && !Number.isNaN(segment.duration)) {
+    const duration = version < 3 ? Math.round(segment.duration) : buildDecimalFloatingNumber(segment.duration, getNumberOfDecimalPlaces(segment.duration));
+    lines.push(`#EXTINF:${duration},${unescape(encodeURIComponent(segment.title || ''))}`);
+  }
   if (segment.byterange) {
     lines.push(`#EXT-X-BYTERANGE:${buildByteRange(segment.byterange)}`);
   }

test/spec/Apple-Low-Latency/New_Media_Playlist_Tags_for_Low-Latency_HLS/03_EXT-X-PART.spec.js

@@ -216,3 +216,18 @@ test('#EXT-X-PART_05', t => {
     }
   }
 });
+
+// EXTINF can be ommitted
+test('#EXT-X-PART_06', t => {
+  utils.bothPass(t, `
+    #EXTM3U
+    #EXT-X-VERSION:6
+    #EXT-X-TARGETDURATION:2
+    #EXT-X-SERVER-CONTROL:CAN-BLOCK-RELOAD=YES,PART-HOLD-BACK=0.6
+    #EXT-X-PART-INF:PART-TARGET=0.2
+    #EXTINF:2,
+    fs240.mp4
+    #EXT-X-PART:DURATION=0.17,URI="fs241.mp4",BYTERANGE=20000@0
+    #EXT-X-ENDLIST
+  `);
+});