Disallow records as part of public API (#4279)

* No public API records

* Add note in contributing

* Explain why

* Fix

CONTRIBUTING.md

@@ -99,6 +99,9 @@ Fabric API makes strong backwards compatibility guarantees, by which contributor
     - If vanilla exposes optionals in return types, then returning an optional is fine.
 - Avoid requiring the user to cast to a subtype if possible.
     - Adding methods to vanilla types can be done via interface injection.
+- Avoid exposing java `record`s as public API.
+    - Records expose more than is necessary for most APIs, which makes them difficult to evolve.
+    - Prefer to expose an interface that is implemented by an impl record.
 
 ### API design patterns to consider
 

checkstyle.xml

@@ -208,5 +208,10 @@
         <module name="MatchXpath">
             <property name="query" value="//VARIABLE_DEF[./TYPE/IDENT[@text='var'] and not(./ASSIGN/EXPR/LITERAL_NEW)]"/>
         </module>
+
+        <!-- Prevent public records in API packages -->
+        <module name="MatchXpath">
+            <property name="query" value="//RECORD_DEF[./MODIFIERS/LITERAL_PUBLIC][//PACKAGE_DEF//DOT/IDENT[@text='api']]"/>
+        </module>
 	</module>
 </module>

fabric-transfer-api-v1/src/main/java/net/fabricmc/fabric/api/transfer/v1/storage/base/ResourceAmount.java

@@ -16,6 +16,8 @@
 
 package net.fabricmc.fabric.api.transfer.v1.storage.base;
 
+//CHECKSTYLE.OFF: MatchXpath
+
 /**
  * An immutable object storing both a resource and an amount, provided for convenience.
  * @param <T> The type of the stored resource.