fix compatibility issue with v3.7 and pre v3.7

Author: topi314

IMPLEMENTATION.md

@@ -1169,22 +1169,34 @@ GET /v3/decodetrack?encodedTrack=BASE64
 
 Response:
 
-[Track Object](#track)
+[Track Object](#track) and [Track Info Object](#track-info) for pre v3.7 compatibility.
 
 <details>
 <summary>Example Payload</summary>
 
 ```yaml
 {
-  "identifier": "dQw4w9WgXcQ",
-  "isSeekable": true,
-  "author": "RickAstleyVEVO",
-  "length": 212000,
-  "isStream": false,
-  "position": 0,
-  "title": "Rick Astley - Never Gonna Give You Up",
-  "uri": "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
-  "sourceName": "youtube"
+  "encoded": "QAAAjQIAJVJpY2sgQXN0bGV5IC0gTmV2ZXIgR29ubmEgR2l2ZSBZb3UgVXAADlJpY2tBc3RsZXlWRVZPAAAAAAADPCAAC2RRdzR3OVdnWGNRAAEAK2h0dHBzOi8vd3d3LnlvdXR1YmUuY29tL3dhdGNoP3Y9ZFF3NHc5V2dYY1EAB3lvdXR1YmUAAAAAAAAAAA==",
+  "info": {
+    "identifier": "dQw4w9WgXcQ",
+    "isSeekable": true,
+    "author": "RickAstleyVEVO",
+    "length": 212000,
+    "isStream": false,
+    "position": 0,
+    "title": "Rick Astley - Never Gonna Give You Up",
+    "uri": "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
+    "sourceName": "youtube"
+  },
+  "identifier": "dQw4w9WgXcQ", // Same as info.identifier, removed in /v4
+  "isSeekable": true, // Same as info.isSeekable, removed in /v4
+  "author": "RickAstleyVEVO", // Same as info.author, removed in /v4
+  "length": 212000, // Same as info.length, removed in /v4
+  "isStream": false, // Same as info.isStream, removed in /v4
+  "position": 0, // Same as info.position, removed in /v4
+  "title": "Rick Astley - Never Gonna Give You Up", // Same as info.title, removed in /v4
+  "uri": "https://www.youtube.com/watch?v=dQw4w9WgXcQ", // Same as info.uri, removed in /v4
+  "sourceName": "youtube" // Same as info.sourceName, removed in /v4
 }
 ```
 

LavalinkServer/src/main/java/lavalink/server/player/AudioLoaderRestHandler.kt

@@ -26,6 +26,7 @@ import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.node.JsonNodeFactory
 import com.fasterxml.jackson.databind.node.ObjectNode
 import com.sedmelluq.discord.lavaplayer.player.AudioPlayerManager
+import dev.arbjerg.lavalink.protocol.v3.DecodedTrack
 import dev.arbjerg.lavalink.protocol.v3.Track
 import dev.arbjerg.lavalink.protocol.v3.TrackInfo
 import dev.arbjerg.lavalink.protocol.v3.decodeTrack
@@ -71,12 +72,13 @@ class AudioLoaderRestHandler(
     }
 
     @GetMapping(value = ["/decodetrack", "/v3/decodetrack"])
-    fun getDecodeTrack(@RequestParam encodedTrack: String?, @RequestParam track: String?): ResponseEntity<TrackInfo> {
+    fun getDecodeTrack(@RequestParam encodedTrack: String?, @RequestParam track: String?): ResponseEntity<DecodedTrack> {
         val trackToDecode = encodedTrack ?: track ?: throw ResponseStatusException(
             HttpStatus.BAD_REQUEST,
             "No track to decode provided"
         )
-        return ResponseEntity.ok(decodeTrack(audioPlayerManager, trackToDecode).toTrack(trackToDecode).info)
+        val decodedTrack = decodeTrack(audioPlayerManager, trackToDecode).toTrack(trackToDecode)
+        return ResponseEntity.ok(DecodedTrack(decodedTrack.encoded, decodedTrack.info, decodedTrack.info))
     }
 
     @PostMapping(value = ["/decodetracks", "/v3/decodetracks"])

protocol/src/main/java/dev/arbjerg/lavalink/protocol/v3/player.kt

@@ -1,5 +1,6 @@
 package dev.arbjerg.lavalink.protocol.v3
 
+import com.fasterxml.jackson.annotation.JsonUnwrapped
 import com.fasterxml.jackson.annotation.JsonValue
 import com.fasterxml.jackson.core.JsonParser
 import com.fasterxml.jackson.databind.DeserializationContext
@@ -21,6 +22,13 @@ data class Player(
     val filters: Filters
 )
 
+data class DecodedTrack(
+    val encoded: String,
+    val info: TrackInfo,
+    @JsonUnwrapped
+    val oldInfo: TrackInfo
+)
+
 data class Track(
     val encoded: String,
     val track: String,