Add extensible crash report header system (#88)

loader/src/main/java/net/neoforged/fml/CrashReportCallables.java

@@ -11,13 +11,16 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.function.BooleanSupplier;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 public class CrashReportCallables
 {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final List<ISystemReportExtender> crashCallables = Collections.synchronizedList(new ArrayList<>());
+    private static final List<ICrashReportHeader> HEADERS = Collections.synchronizedList(new ArrayList<>());
 
     /**
      * Register a custom {@link ISystemReportExtender}
@@ -90,8 +93,21 @@ public boolean isActive()
         });
     }
 
+    /**
+     * Registers a header to be added to the top of crash reports.
+     *
+     * @param header the header
+     */
+    public static void registerHeader(ICrashReportHeader header) {
+        HEADERS.add(header);
+    }
+
     public static List<ISystemReportExtender> allCrashCallables()
     {
         return List.copyOf(crashCallables);
     }
+
+    public static Stream<String> getHeaders() {
+        return HEADERS.stream().map(ICrashReportHeader::getHeader).filter(Objects::nonNull);
+    }
 }

loader/src/main/java/net/neoforged/fml/ICrashReportHeader.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.fml;
+
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Supplies a header to add to crash reports.
+ * @see CrashReportCallables#registerHeader(ICrashReportHeader)
+ */
+@FunctionalInterface
+public interface ICrashReportHeader {
+    /**
+     * {@return the header to be displayed at the top of the crash report, or {@code null} if the header shouldn't be added}
+     */
+    @Nullable
+    String getHeader();
+}

loader/src/main/java/net/neoforged/fml/ISystemReportExtender.java

@@ -5,14 +5,16 @@
 
 package net.neoforged.fml;
 
+import org.jetbrains.annotations.ApiStatus;
+
 import java.util.function.Supplier;
 
+@ApiStatus.OverrideOnly
 public interface ISystemReportExtender extends Supplier<String>
 {
     String getLabel();
 
-    default boolean isActive()
-    {
+    default boolean isActive() {
         return true;
     }
 }