Lenient metadata parsing

src/main/java/dev/rdh/sarcio/mixin/resourcepacks/CustomResourcePackMetadataMixin.java

@@ -0,0 +1,23 @@
+package dev.rdh.sarcio.mixin.resourcepacks;
+
+import dev.rdh.sarcio.util.LenientJson;
+
+import net.minecraft.client.resource.pack.CustomResourcePack;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+@Mixin(CustomResourcePack.class)
+abstract class CustomResourcePackMetadataMixin {
+    @ModifyVariable(
+            method = "getMetadataSection(Lnet/minecraft/client/resource/metadata/ResourceMetadataSerializers;Ljava/io/InputStream;Ljava/lang/String;)Lnet/minecraft/client/resource/metadata/ResourceMetadataSection;",
+            at = @At("HEAD"),
+            argsOnly = true
+    )
+    private static InputStream sarcio$dropUnknownEscapes(InputStream in) throws IOException {
+        return LenientJson.dropUnknownEscapes(in);
+    }
+}

src/main/java/dev/rdh/sarcio/mixin/resourcepacks/JsonResourceMetadataMixin.java

@@ -0,0 +1,23 @@
+package dev.rdh.sarcio.mixin.resourcepacks;
+
+import dev.rdh.sarcio.util.LenientJson;
+
+import net.ornithemc.osl.resource.loader.impl.resource.JsonResourceMetadata;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+@Mixin(JsonResourceMetadata.class)
+abstract class JsonResourceMetadataMixin {
+    @ModifyVariable(
+            method = "fromInputStream(Ljava/io/InputStream;)Lnet/ornithemc/osl/resource/loader/impl/resource/JsonResourceMetadata;",
+            at = @At("HEAD"),
+            argsOnly = true
+    )
+    private static InputStream sarcio$dropUnknownEscapes(InputStream is) throws IOException {
+        return LenientJson.dropUnknownEscapes(is);
+    }
+}

src/main/java/dev/rdh/sarcio/util/LenientJson.java

@@ -0,0 +1,20 @@
+package dev.rdh.sarcio.util;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.regex.Pattern;
+
+public class LenientJson {
+	private static final Pattern VALID_ESCAPE_OR_STRAY_BACKSLASH = Pattern.compile("(\\\\[\"\\\\/bfnrtu'\\n])|\\\\");
+	private static final String KEEP_VALID_ESCAPE = "$1";
+
+	public static InputStream dropUnknownEscapes(InputStream in) throws IOException {
+		try (InputStream stream = in) {
+			String json = new String(stream.readAllBytes(), StandardCharsets.UTF_8);
+			String cleaned = VALID_ESCAPE_OR_STRAY_BACKSLASH.matcher(json).replaceAll(KEEP_VALID_ESCAPE);
+			return new ByteArrayInputStream(cleaned.getBytes(StandardCharsets.UTF_8));
+		}
+	}
+}

src/main/resources/sarcio.mixins.json

@@ -132,6 +132,8 @@
     "resourcepacks.CustomResourcePackMixin",
     "resourcepacks.BuiltInResourcePackMixin",
     "resourcepacks.AssetIndexMixin",
+    "resourcepacks.CustomResourcePackMetadataMixin",
+    "resourcepacks.JsonResourceMetadataMixin",
     "textures.TextureManagerMixin",
     "textures.TextureUtilMixin",
     "textures.HttpTextureMixin",