Documentation Docs/en/reference/prototype-format/validation.md

Prototype Validation Rules

Generated reference. Do not edit directly. Update BuildTools/PrototypeFormatInterface.json or the owning engine metadata, then run python BuildTools/docs_prototype_format.py --write.

Index

Syntax

These rules are enforced by the parser, metadata registrators, property serializer, or the side-specific prototype bake. Stable IDs let CI track contract changes.

Stable ID	Rule	Requirement	Notes	Authority
`prototype-format.rule.config-syntax`	Configuration syntax	Use repeated INI-like sections, key = value assignments, # comments, whitespace-prefixed trailing backslash continuation, and key += value append where appropriate.	Prototype files use the shared ConfigFile parser; quoted or escaped comment characters remain part of the value.	Source/Common/ConfigFile.cpp
`prototype-format.rule.file-filter`	Extension filter	Only files whose extension occurs in Baking.ProtoFileExtensions enter ProtoBaker.	Directories and conventional extension names do not select a prototype type; the section does.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.identity-per-type`	Identity and duplicates	A migration-resolved prototype id must be unique within its resolved type across the complete pack input.	The same text id may exist in different prototype types; duplicate ids in one type fail the bake.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.identifier-characters`	Reserved identifier characters	Prototype ids must not contain / or $ because both characters are reserved for nested section addressing.	The baker rejects either character after applying the file-basename fallback and before hashing or duplicate detection.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.inheritance-scope`	Inheritance scope	Every parent must resolve inside the same prototype type and current pack input.	Parents may be declared in another file, but cross-type and missing parents fail the bake.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.inheritance-precedence`	Inheritance precedence	Merge ancestors depth first, then parents from left to right, then the child; later property values replace earlier values.	$-prefixed control directives are not copied into the merged property map.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.acyclic-inheritance`	Acyclic inheritance	Prototype parent graphs must be acyclic.	ProtoBaker and ProtoTextBaker track the active parent path and reject self, pair, and longer cycles under every repeated-parent policy.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.repeated-ancestors`	Repeated ancestors	A parent reached through several inheritance paths contributes only where it is first reached; Baking.AllowRepeatedProtoParents decides whether the later reach is skipped or rejected.	The default is permissive; set the option false when a project wants every inheritance diamond to fail baking. ProtoBaker and ProtoTextBaker apply the same rule.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.property-resolution`	Property resolution	Every non-control key must resolve to a property available for the current bake side.	Unknown, disabled-for-this-side, virtual, and temporary properties are rejected; opposite-side-only properties are skipped for that side.	Source/Common/Properties.cpp
`prototype-format.rule.strict-values`	Strict text values	Property values must parse according to the metadata type without overflow, unknown enum/prototype references, non-finite numbers, or malformed collection structure.	The property serializer is the authority for scalar, enum, struct, array, dictionary, RefType, FixedType, and Proto reference text.	Source/Common/PropertiesSerializer.cpp
`prototype-format.rule.init-script-signature`	InitScript callback signatures	A non-empty built-in Item, Critter, Map, or Location InitScript property must resolve to a global void callback receiving that entity type and bool firstTime.	Server baking validates ScriptFuncType metadata for every authored callback property and rejects missing functions or mismatched signatures before runtime.	Source/Tools/Baker.cpp
`prototype-format.rule.proto-reference`	Prototype references	FixedType and Proto entity property references must resolve after migration unless the property is nullable and the authored value is empty.	A removed or renamed referenced id needs an explicit Proto migration rule to a valid target or Remove according to the owning persistence policy.	Source/Common/PropertiesSerializer.cpp
`prototype-format.rule.proto-migration`	Prototype migration	Proto migration rules are applied to declared ids, parent ids, lookups, and persisted references before final resolution.	Author migrations in native/project metadata with ///@ MigrationRule Proto <Type> <Old> <NewOrRemove>.	Source/Tools/ProtoBaker.cpp
`prototype-format.rule.side-specific-output`	Side-specific output	The same source set is parsed and serialized separately for server, client, and mapper metadata.	A source property can be meaningful on one side and skipped on another; server output also validates script callback properties.	Source/Tools/ProtoBaker.cpp

Current diagnostic limitation

Parent graphs must be acyclic. The current baker recursively expands parents without a dedicated cycle diagnostic, so embedding projects should validate cycles before baking and keep inheritance chains shallow. This is a documented implementation limitation, not a supported cyclic behavior.