Paper/Spigot-Server-Patches/0683-Throw-proper-exception-on-empty-JsonList-file.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Mariell Hoversholm <proximyst@proximyst.com>
Date: Sun, 1 Nov 2020 16:43:11 +0100
Subject: [PATCH] Throw proper exception on empty JsonList file


diff --git a/src/main/java/net/minecraft/server/JsonList.java b/src/main/java/net/minecraft/server/JsonList.java
index 1fc0139cb9694ddea41f57d95774c3b47e8530c5..8da5f976109accc84b26ec4045776aa8a9799f3d 100644
--- a/src/main/java/net/minecraft/server/JsonList.java
+++ b/src/main/java/net/minecraft/server/JsonList.java
@@ -187,6 +187,7 @@ public abstract class JsonList<K, V extends JsonListEntry<K>> {
 
             try {
                 JsonArray jsonarray = (JsonArray) JsonList.b.fromJson(bufferedreader, JsonArray.class);
+                com.google.common.base.Preconditions.checkState(jsonarray != null, "The file \"" + this.c.getName() + "\" is either empty or corrupt"); // Paper
 
                 this.d.clear();
                 Iterator iterator = jsonarray.iterator();
Throw proper exception on empty JsonList file Related to #4174, #4717. As it stands, `JsonList` throws an NPE on `jsonarray.iterator()` when the reader given is at EOF. This means there is an unintelligible message shown to the player: ``` [16:44:31 ERROR]: Encountered an unexpected exception java.lang.NullPointerException: Cannot invoke "com.google.gson.JsonArray.iterator()" because "jsonarray" is null at net.minecraft.server.v1_16_R2.JsonList.load(JsonList.java:192) ~[patched_1.16.3.jar:git-Paper-248] at net.minecraft.server.v1_16_R2.DedicatedPlayerList.y(SourceFile:95) ~[patched_1.16.3.jar:git-Paper-248] ... ``` This is clearly not understandable to the untrained eye: what is `jsonarray`? What is `DedicatedPlayerList.y`? This rather does a proper exception message: ``` [16:42:59 ERROR]: Encountered an unexpected exception java.lang.NullPointerException: The file "banned-players.json" is either empty or corrupt at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:787) ~[paper-1.16.3.jar:git-Paper-"8e6d90c2d"] at net.minecraft.server.v1_16_R2.JsonList.load(JsonList.java:190) ~[paper-1.16.3.jar:git-Paper-"8e6d90c2d"] at net.minecraft.server.v1_16_R2.DedicatedPlayerList.y(SourceFile:95) ~[paper-1.16.3.jar:git-Paper-"8e6d90c2d"] ... ``` It is still an exception, which server owners may or may not understand, but the message now says exactly what went wrong, and who would've known, now we know what `DedicatedPlayerList.y` is, and we know what file was broken. This is more of a quality of life change, but it is certainly useful to the server owners that come into `#paper-help` and the issue tracker (#4174) to ask for help with unintelligible messages we need to open a patched Paper project to make any sense out of. Check state of jsonarray instead of checkNotNull Co-authored-by: Riley Park <riley.park@meino.net> 2020-11-01 16:43:31 +01:00			`From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001`
			`From: Mariell Hoversholm <proximyst@proximyst.com>`
			`Date: Sun, 1 Nov 2020 16:43:11 +0100`
			`Subject: [PATCH] Throw proper exception on empty JsonList file`


			`diff --git a/src/main/java/net/minecraft/server/JsonList.java b/src/main/java/net/minecraft/server/JsonList.java`
			`index 1fc0139cb9694ddea41f57d95774c3b47e8530c5..8da5f976109accc84b26ec4045776aa8a9799f3d 100644`
			`--- a/src/main/java/net/minecraft/server/JsonList.java`
			`+++ b/src/main/java/net/minecraft/server/JsonList.java`
			`@@ -187,6 +187,7 @@ public abstract class JsonList<K, V extends JsonListEntry<K>> {`

			`try {`
			`JsonArray jsonarray = (JsonArray) JsonList.b.fromJson(bufferedreader, JsonArray.class);`
			`+ com.google.common.base.Preconditions.checkState(jsonarray != null, "The file \"" + this.c.getName() + "\" is either empty or corrupt"); // Paper`

			`this.d.clear();`
			`Iterator iterator = jsonarray.iterator();`