Breaking changes in 6.0

Breaking changes

• Removed the IDeepCopyable interface, which was previously implemented on our POCOs. Its methods are now accessible via extensions.
• Removed IsResource from the FhirTypeAttribute. One can just check against the Resource subtype instead.
• Renamed the IsNestedType parameter on FhirTypeAttribute to IsBackboneType to align with common FHIR jargon.
• Removed the BackboneTypeAttribute class. One can use IsBackboneType (above), the type's name (that was in this attribute) is now the ClassMapping.Name.
• Removed the DefinitionPath property of ClassMapping, since it is the same as the ClassMapping.Name for backbone types.
• POCO's no longer implement IDictionary<string,object>. Although this sounded like a good idea, it did break frameworks and made the debuggers display resoures as dictionaries. The interface is also not enough to base serializers or validators on, so it's use is limited. Therefore, we decided to remove it. You can now use EnumerateElements() instead, or functions like TryGetValue() and SetValue and the indexer ([]).
• Since we now have a standard way to dynamically navigate a POCO, we removed Base.Children and Base.NamedChildren properties, since these have overlapping functionalities. Note that there is an extension method Children() (obsolete) that you can use for backwards-compatibility.
• The type of ElementDefinition.Constraint.RequirementsElement, ElementDefinition.Binding.DescriptionElement, ElementDefinition.Mapping.CommentElement and CapabilityStatement.Implementation.DescriptionElement have changed from Markdown to PrimitiveType. Set this property to Markdown to get the original behaviour. This change allows you to use the correct type depending on the version of FHIR you are writing against (which matters in e.g. FhirPath expressions that match against type).
• The type of Attachment.SizeElement has changed from Integer64 to PrimitiveType. Set this property to Integer64 to get the original behaviour, but you should now assign the correct type (i.e. UnsignedInteger before R5) depending on the version of FHIR you are writing against.
• The type of Bundle.Link.RelationElement has changed from FhirString to PrimitiveType. Set this property to Integer64 to get the original behaviour, but you can now use the correct type depending on the version of FHIR you are writing against.
• The type of Meta.ProfileElement has changed from Canonical to Code. Set this property to Integer64 to get the original behaviour, but you can now use the correct type depending on the version of FHIR you are writing against.
• Each of the above elements no have multiple helper properties (e.g. Attachment.Size and Attachment.SizeUnsignedInteger) to allow you to use "simple assignments" of primitives.
• IAnnotatable now inherits IAnnotated, so implementers of the former will have to implement the latter. Which makes sense, since objects that can be annotated should provide support for reading those annotations too.
• Resource.HasVersionId has been removed as part of a clean up of the public interface of Resource. Just check Resource.VersionId for null.
• Resource.SyncLock has been removed, as this is not a responsibility for Resource, and lock objects will change in .NET 9.
• The IDeepComparable interface has disappeared, the Matches() and IsExactly() functions now simply take a Base as parameter. Also, it is now possible to write new custom comparison operations using the new CompareChildren() function, given a custom implementation of IEqualityComparer<T>.

Breaking changes to the serializers

All the settings classes for serializers (FhirJson/XmlSerializationSettings, SerializerSettings, FhirJsonPocoSerializerSettings) have been taken out:

• Pretty printing is not a configuration, but has returned as a parameter to serialization functions that produce a string or bytearray.
• There is no longer a way to throw an exception if the serializer encounters an unknown element: this kind of "validation" is part of the parser and validator, and felt rather out of place in the serializer (which, by design, does not do any other kind of validation).
• Summary filters can be passed as arguments to the serialization functions, since they are not a constant configuration option for a serializer, as the kind of summarization may vary from call to call to the serializer. This also meant removing the IncludeMandatoryElementsInSummary setting, as this should now be controlled by constructing a summary filter using SerializationFilter.ForSummary(), which has a parameter to control this setting. This filter is then passed as an argument to the serializer calls (or as an option to ForFhir()).
• The ability to control trimming whitespace in XML values has been removed since the FHIR specification demands whitespace is always trimmed.
• Most async versions of the serializers have been removed since we are using XmlWriter for Xml and have switched from Newtonsoft to System.Text.Json.Utf8JsonWriter internally, all of which have no support for async.
• When configuring the System.Text.Json stack with ForFhir(), you no longer have to pass in separate serializer and deserializer option structures, they have both been combined into a single FhirJsonConverterOptions.
• The BaseFhirPocoXml/JsonSerializer took a FhirRelease as a constructor argument, while all other multi-version classes (like BaseFhirClient) took a ModelInspector. We have made this consistent by letting the serializers have a ModelInspector argument.

Removed obsolete members

Behavioural changes

• We have archived the Fhir.Metrics library. This means that Types/Quantity no longer supports UCUM unit conversion. Comparing units will now only succeed if the units are equivalent, at which point they are compared by value.
• Narrative.div and Narrative.status are no longer in-summary (to reflect corrections made to this effect in the FHIR spec). This will result in a different rendering of resources when generating summaries.

Minor/exotic breaking changes

• Parameters.this[] has been removed in favor of a (future) use of this operator on the base, e.g. for dynamic access to elements. You can use the existing (and equivalent) GetSingle() instead.
• ReflectionHelper.IsTypedCollection(System.Type) has been renamed to ReflectionHelper.IsTypedList(System.Type) since checking against ICollection<T> is not sufficient anymore to determine whether an element's type is a List, so we check against IList<T> instead.
• The type of FhirEvaluationContext.TerminologyService has been changed from ITerminologyService to ICodeValidationTerminologyService. For most users, this should not be breaking.
• The WithResourceOverrides static method introduced in 5.10 is now an extension method (and will need to be called on an instance). This allows subclasses to inherit it without implementing it themselves.
• Moved ScopedNodeExtensions from the ElementModel namespace to the Model namespace. Import Hl7.Fhir.Model when using methods like Resolve()
• The type of FhirEvaluationContext.ElementResolver has been changed from Func<string, ITypedElement> to Func<string, IScopedNode>. External resolvers should make sure to return a scoped node.
• The DefaultModelFactory has been removed. It had not been in use for years, except by our own tests. With the cleanup of the PocoBuilder (ITypedElement->POCO) infrastructure, we decided to remove this class.
• CitedArtifactContributorshipSummaryComponent has been renamed to the more correct ContributorshipSummaryComponent.