Regular expressions in Scarpet can return Java null

Question

Regular expressions in Scarpet can return Java null

CommandLeo opened this issue 2 years ago · 4 comments

CommandLeo commented 2 years ago

To reproduce run the following line of code: ''~'(.)?'

James103 · Answer 1 · 2022-09-04T18:44:36.000Z

Set carpet superSecretSetting true, try reproducing this again, then check the server log. Post the full exception here if avaliable.

CommandLeo · Answer 2 · 2022-09-22T18:18:15.000Z

In my opinion in this case it should return null, to be consistent with the result of ''~'(.)'

CommandLeo · Answer 3 · 2022-09-11T13:35:48.000Z

java.lang.NullPointerException: Cannot invoke "String.trim()" because "in" is null
	at Not Enough Crashes deobfuscated stack trace.(1.17.1+build.65) ~[?:?]
	at jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1838) ~[?:?]
	at jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110) ~[?:?]
	at java.lang.Double.parseDouble(Double.java:651) ~[?:?]
	at java.lang.Double.valueOf(Double.java:614) ~[?:?]
	at carpet.script.value.Value.readDoubleNumber(Value.java:201) ~[fabric-carpet-1.18.2-1.4.69+v220331.jar:?]
	at carpet.script.value.Value.readInteger(Value.java:211) ~[fabric-carpet-1.18.2-1.4.69+v220331.jar:?]
	at carpet.commands.ScriptCommand.handleCall(ScriptCommand.java:453) ~[fabric-carpet-1.18.2-1.4.69+v220331.jar:?]
	at carpet.commands.ScriptCommand.compute(ScriptCommand.java:505) ~[fabric-carpet-1.18.2-1.4.69+v220331.jar:?]
	at carpet.commands.ScriptCommand.lambda$register$17(ScriptCommand.java:144) ~[fabric-carpet-1.18.2-1.4.69+v220331.jar:?]
	at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:263) ~[brigadier-1.0.18.jar:?]
	at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:177) ~[brigadier-1.0.18.jar:?]
	at net.minecraft.server.command.CommandManager.execute(CommandManager:264) ~[?:?]
	at net.minecraft.server.network.ServerPlayNetworkHandler.executeCommand(ServerPlayNetworkHandler:1253) ~[?:?]
	at net.minecraft.server.network.ServerPlayNetworkHandler.handleMessage(ServerPlayNetworkHandler:1237) ~[?:?]
	at net.minecraft.server.network.ServerPlayNetworkHandler.onGameMessage(ServerPlayNetworkHandler:1220) ~[?:?]
	at net.minecraft.network.packet.c2s.play.ChatMessageC2SPacket.apply(ChatMessageC2SPacket:30) ~[?:?]
	at net.minecraft.network.packet.c2s.play.ChatMessageC2SPacket.apply(ChatMessageC2SPacket:7) ~[?:?]
	at net.minecraft.network.NetworkThreadUtils.method_11072(NetworkThreadUtils:22) ~[?:?]
	at net.minecraft.server.ServerTask.run(ServerTask:18) ~[?:?]
	at net.minecraft.util.thread.ThreadExecutor.executeTask(ThreadExecutor:157) ~[?:?]
	at net.minecraft.util.thread.ReentrantThreadExecutor.executeTask(ReentrantThreadExecutor:23) ~[?:?]
	at net.minecraft.server.MinecraftServer.executeTask(MinecraftServer:808) ~[client-intermediary.jar:?]
	at net.minecraft.server.MinecraftServer.executeTask(MinecraftServer:165) ~[client-intermediary.jar:?]
	at net.minecraft.util.thread.ThreadExecutor.runTask(ThreadExecutor:131) ~[?:?]
	at net.minecraft.server.MinecraftServer.runOneTask(MinecraftServer:790) ~[client-intermediary.jar:?]
	at net.minecraft.server.MinecraftServer.runTask(MinecraftServer:784) ~[client-intermediary.jar:?]
	at net.minecraft.util.thread.ThreadExecutor.runTasks(ThreadExecutor:140) ~[?:?]
	at net.minecraft.server.MinecraftServer.runTasksTillTickEnd(MinecraftServer:769) ~[client-intermediary.jar:?]
	at net.minecraft.server.MinecraftServer.handler$zde000$modifiedRunLoop(MinecraftServer:2905) ~[client-intermediary.jar:?]
	at net.minecraft.server.MinecraftServer.runServer(MinecraftServer:676) ~[client-intermediary.jar:?]
	at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer:273) ~[client-intermediary.jar:?]
	at java.lang.Thread.run(Thread.java:833) [?:?]
	```

altrisi · Answer 4 · 2022-09-22T10:10:28.000Z

So I know where this happens, but I don't know what the correct behaviour would be given I don't know regex much.

Should this return an empty list, null or a list with a null element?

The scarpet docs specify the following:

null if there is no match

matched phrase if no grouping is applied

matched element if one group is applied

list of matches if more than one grouping is applied

Now, from what I can get out of the javadocs for what scarpet uses, this match got 1 group (from the groupCount call), but given null is returned:

the match was successful but the group specified failed to match any part of the input sequence

(Matcher Javadoc).

Then the issue is carpet doesn't expect null there, but a String, and therefore it's introducing a broken value.

I think this should be scarpet null from a quick look, though I'd prefer more opinions on this.

There also needs to be thought on what if there's multiple groups, because I'm quite sure if there's multiple groups matching this way scarpet will also also introduce broken values.

Share to