Upgrade SnapshotSource to support async resolvers

src/Benchmarks/EnumUtilityBenchmarks.cs

@@ -3,6 +3,8 @@
 using Hl7.Fhir.Utility;
 using System;
 
+#nullable enable
+
 namespace Firely.Sdk.Benchmarks
 {
     [MemoryDiagnoser]
@@ -16,7 +18,7 @@ public string EnumToString()
             => SearchParamType.String.ToString();
 
         [Benchmark]
-        public string EnumGetName()
+        public string? EnumGetName()
             => Enum.GetName(StringSearchParam);
 
         [Benchmark]
@@ -37,26 +39,27 @@ public SearchParamType EnumParseIgnoreCase()
 
         [Benchmark]
         public SearchParamType EnumUtilityParseLiteral()
-            => EnumUtility.ParseLiteral<SearchParamType>("string").Value;
+            => EnumUtility.ParseLiteral<SearchParamType>("string")!.Value;
 
         [Benchmark]
-        public Enum EnumUtilityParseLiteralNonGeneric()
+        public Enum? EnumUtilityParseLiteralNonGeneric()
             => EnumUtility.ParseLiteral("string", typeof(SearchParamType));
 
         [Benchmark]
         public SearchParamType EnumUtilityParseLiteralIgnoreCase()
-            => EnumUtility.ParseLiteral<SearchParamType>("string", true).Value;
+            => EnumUtility.ParseLiteral<SearchParamType>("string", true)!.Value;
 
         [Benchmark]
-        public Enum EnumUtilityParseLiteralIgnoreCaseNonGeneric()
+        public Enum? EnumUtilityParseLiteralIgnoreCaseNonGeneric()
             => EnumUtility.ParseLiteral("string", typeof(SearchParamType), true);
 
         [Benchmark]
         public string? EnumUtilityGetSystem()
             => EnumUtility.GetSystem(StringSearchParam);
 
         [Benchmark]
-        public string EnumUtilityGetSystemNonGeneric()
+        public string? EnumUtilityGetSystemNonGeneric()
             => EnumUtility.GetSystem(StringSearchParamEnum);
     }
 }
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/Adapters/ScopedNodeToTypedElementAdapter.cs

@@ -0,0 +1,47 @@
+/* 
+ * Copyright (c) 2023, Firely ([email protected]) and contributors
+ * See the file CONTRIBUTORS for details.
+ * 
+ * This file is licensed under the BSD 3-Clause license
+ * available at https://raw.githubusercontent.com/FirelyTeam/firely-net-sdk/master/LICENSE
+ */
+
+#nullable enable
+
+using Hl7.Fhir.Specification;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Hl7.Fhir.ElementModel
+{
+    /// <summary>
+    /// An adapter from <see cref="IScopedNode"/> to <see cref="ITypedElement"/>.
+    /// </summary>
+    /// <remarks>Be careful, this adapter does not implement the <see cref="ITypedElement.Location"/> and 
+    /// <see cref="ITypedElement.Definition"/> property.
+    /// </remarks>
+    internal class ScopedNodeToTypedElementAdapter : ITypedElement
+    {
+        private readonly IScopedNode _adaptee;
+
+        public ScopedNodeToTypedElementAdapter(IScopedNode adaptee)
+        {
+            _adaptee = adaptee;
+        }
+
+        public string Location => throw new System.NotImplementedException();
+
+        public IElementDefinitionSummary Definition => throw new System.NotImplementedException();
+
+        public string Name => _adaptee.Name;
+
+        public string InstanceType => _adaptee.InstanceType;
+
+        public object Value => _adaptee.Value;
+
+        public IEnumerable<ITypedElement> Children(string? name = null) =>
+            _adaptee.Children(name).Select(n => new ScopedNodeToTypedElementAdapter(n));
+    }
+}
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/ElementNodeExtensions.cs

@@ -108,5 +108,14 @@ public static IReadOnlyCollection<IElementDefinitionSummary> ChildDefinitions(th
 
         public static ScopedNode ToScopedNode(this ITypedElement node) =>
             node as ScopedNode ?? new ScopedNode(node);
+
+        /// <summary>
+        /// Convert a <see cref="ITypedElement"/> to a <see cref="IScopedNode"/>.
+        /// </summary>
+        /// <param name="node">An <see cref="ITypedElement"/></param>
+        /// <returns></returns>
+        public static IScopedNode AsScopedNode(this ITypedElement node) => ToScopedNode(node);
     }
 }
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/IBaseElementNavigator.cs

@@ -0,0 +1,67 @@
+/* 
+ * Copyright (c) 2023, Firely ([email protected]) and contributors
+ * See the file CONTRIBUTORS for details.
+ * 
+ * This file is licensed under the BSD 3-Clause license
+ * available at https://raw.githubusercontent.com/FirelyTeam/firely-net-sdk/master/LICENSE
+ */
+
+using System.Collections.Generic;
+
+#nullable enable
+
+namespace Hl7.Fhir.ElementModel
+{
+    /// <summary>
+    /// The base interface for <see cref="ITypedElement"/> and <see cref="IScopedNode"/>."/>
+    /// </summary>
+    /// <typeparam name="TDerived"></typeparam>
+    public interface IBaseElementNavigator<TDerived> where TDerived : IBaseElementNavigator<TDerived>
+    {
+        /// <summary>
+        /// Enumerate the child nodes present in the source representation (if any)
+        /// </summary>
+        /// <param name="name">Return only the children with the given name.</param>
+        /// <returns></returns>
+        IEnumerable<TDerived> Children(string? name = null);
+
+        /// <summary>
+        /// Name of the node, e.g. "active", "value".
+        /// </summary>
+        string Name { get; }
+
+        /// <summary>
+        /// Type of the node. If a FHIR type, this is just a simple string, otherwise a StructureDefinition url for a type defined as a logical model.
+        /// </summary>
+        string InstanceType { get; }
+
+        /// <summary>
+        /// The value of the node (if it represents a primitive FHIR value)
+        /// </summary>
+        /// <remarks>
+        /// FHIR primitives are mapped to underlying C# types as follows:
+        ///
+        /// instant         Hl7.Fhir.ElementModel.Types.DateTime
+        /// time            Hl7.Fhir.ElementModel.Types.Time
+        /// date            Hl7.Fhir.ElementModel.Types.Date
+        /// dateTime        Hl7.Fhir.ElementModel.Types.DateTime
+        /// decimal         decimal
+        /// boolean         bool
+        /// integer         int
+        /// unsignedInt     int
+        /// positiveInt     int
+        /// long/integer64  long (name will be finalized in R5)
+        /// string          string
+        /// code            string
+        /// id              string
+        /// uri, oid, uuid, 
+        /// canonical, url  string
+        /// markdown        string
+        /// base64Binary    string (uuencoded)
+        /// xhtml           string
+        /// </remarks>
+        object Value { get; }
+    }
+}
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/IScopedNode.cs

@@ -0,0 +1,29 @@
+/* 
+ * Copyright (c) 2023, Firely ([email protected]) and contributors
+ * See the file CONTRIBUTORS for details.
+ * 
+ * This file is licensed under the BSD 3-Clause license
+ * available at https://raw.githubusercontent.com/FirelyTeam/firely-net-sdk/master/LICENSE
+ */
+
+#nullable enable
+
+namespace Hl7.Fhir.ElementModel
+{
+    /// <summary>
+    /// An element within a tree of typed FHIR data with also a parent element.
+    /// </summary>
+    /// <remarks>
+    /// This interface represents FHIR data as a tree of elements, including type information either present in 
+    /// the instance or derived from fully aware of the FHIR definitions and types
+    /// </remarks>
+    public interface IScopedNode : IBaseElementNavigator<IScopedNode>
+    {
+        /// <summary>
+        /// The parent node of this node, or null if this is the root node.
+        /// </summary>
+        IScopedNode? Parent { get; }
+    }
+}
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/IScopedNodeExtensions.cs

@@ -0,0 +1,42 @@
+/* 
+ * Copyright (c) 2023, Firely ([email protected]) and contributors
+ * See the file CONTRIBUTORS for details.
+ * 
+ * This file is licensed under the BSD 3-Clause license
+ * available at https://raw.githubusercontent.com/FirelyTeam/firely-net-sdk/master/LICENSE
+ */
+
+#nullable enable
+
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Hl7.Fhir.ElementModel
+{
+    public static class IScopedNodeExtensions
+    {
+        /// <summary>
+        /// Converts a <see cref="IScopedNode"/> to a <see cref="ITypedElement"/>.
+        /// </summary>
+        /// <param name="node">An <see cref="IScopedNode"/> node</param>
+        /// <returns>An implementation of <see cref="ITypedElement"/></returns>
+        /// <remarks>Be careful when using this method, the returned <see cref="ITypedElement"/> does not implement
+        /// the methods <see cref="ITypedElement.Location"/> and <see cref="ITypedElement.Definition"/>.    
+        /// </remarks>
+        public static ITypedElement AsTypedElement(this IScopedNode node) =>
+            node is ITypedElement ite ? ite : new ScopedNodeToTypedElementAdapter(node);
+
+        /// <summary>
+        /// Returns the parent resource of this node, or null if this node is not part of a resource.
+        /// </summary>
+        /// <param name="nodes"></param>
+        /// <param name="name"></param>
+        /// <returns></returns>
+        public static IEnumerable<IScopedNode> Children(this IEnumerable<IScopedNode> nodes, string? name = null) =>
+           nodes.SelectMany(n => n.Children(name));
+
+    }
+}
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/ITypedElement.cs

@@ -7,7 +7,6 @@
  */
 
 using Hl7.Fhir.Specification;
-using System.Collections.Generic;
 
 namespace Hl7.Fhir.ElementModel
 {
@@ -19,51 +18,9 @@ namespace Hl7.Fhir.ElementModel
     /// the instance or derived from fully aware of the FHIR definitions and types
     /// </remarks>
 
-    public interface ITypedElement
+    public interface ITypedElement : IBaseElementNavigator<ITypedElement>
     {
-        /// <summary>
-        /// Enumerate the child nodes present in the source representation (if any)
-        /// </summary>
-        /// <param name="name">Return only the children with the given name.</param>
-        /// <returns></returns>
-        IEnumerable<ITypedElement> Children(string name = null);
-
-        /// <summary>
-        /// Name of the node, e.g. "active", "value".
-        /// </summary>
-        string Name { get; }
 
-        /// <summary>
-        /// Type of the node. If a FHIR type, this is just a simple string, otherwise a StructureDefinition url for a type defined as a logical model.
-        /// </summary>
-        string InstanceType { get; }
-
-        /// <summary>
-        /// The value of the node (if it represents a primitive FHIR value)
-        /// </summary>
-        /// <remarks>
-        /// FHIR primitives are mapped to underlying C# types as follows:
-        ///
-        /// instant         Hl7.Fhir.ElementModel.Types.DateTime
-        /// time            Hl7.Fhir.ElementModel.Types.Time
-        /// date            Hl7.Fhir.ElementModel.Types.Date
-        /// dateTime        Hl7.Fhir.ElementModel.Types.DateTime
-        /// decimal         decimal
-        /// boolean         bool
-        /// integer         int
-        /// unsignedInt     int
-        /// positiveInt     int
-        /// long/integer64  long (name will be finalized in R5)
-        /// string          string
-        /// code            string
-        /// id              string
-        /// uri, oid, uuid, 
-        /// canonical, url  string
-        /// markdown        string
-        /// base64Binary    string (uuencoded)
-        /// xhtml           string
-        /// </remarks>
-        object Value { get; }
 
         /// <summary>
         /// An indication of the location of this node within the data represented by the <c>ITypedElement</c>.

src/Hl7.Fhir.Base/ElementModel/ScopedNode.cs

@@ -16,7 +16,7 @@
 
 namespace Hl7.Fhir.ElementModel
 {
-    public class ScopedNode : ITypedElement, IAnnotated, IExceptionSource
+    public class ScopedNode : ITypedElement, IScopedNode, IAnnotated, IExceptionSource
     {
         private class Cache
         {
@@ -45,6 +45,7 @@ public ScopedNode(ITypedElement wrapped, string? instanceUri = null)
         private ScopedNode(ScopedNode parentNode, ScopedNode? parentResource, ITypedElement wrapped, string? fullUrl)
         {
             Current = wrapped;
+            Parent = parentNode;
             ExceptionHandler = parentNode.ExceptionHandler;
             ParentResource = parentNode.AtResource ? parentNode : parentResource;
 
@@ -217,8 +218,7 @@ public string? InstanceUri
             {
                 // Scan up until the first parent that knowns the instance uri (at the last the
                 // root, if it has been supplied).
-                if (_cache.InstanceUri is null)
-                    _cache.InstanceUri = ParentResources().SkipWhile(p => p.InstanceUri is null).FirstOrDefault()?.InstanceUri;
+                _cache.InstanceUri ??= ParentResources().SkipWhile(p => p.InstanceUri is null).FirstOrDefault()?.InstanceUri;
 
                 return _cache.InstanceUri;
             }
@@ -229,11 +229,22 @@ private set
             }
         }
 
+        /// <inheritdoc />
+        public IScopedNode? Parent { get; private set; }
+
         /// <inheritdoc />
         public IEnumerable<object> Annotations(Type type) => type == typeof(ScopedNode) ? (new[] { this }) : Current.Annotations(type);
 
+        private IEnumerable<ScopedNode> childrenInternal(string? name = null) =>
+            Current.Children(name).Select(c => new ScopedNode(this, ParentResource, c, _fullUrl));
+
         /// <inheritdoc />
         public IEnumerable<ITypedElement> Children(string? name = null) =>
-            Current.Children(name).Select(c => new ScopedNode(this, ParentResource, c, _fullUrl));
+             childrenInternal(name);
+
+        IEnumerable<IScopedNode> IBaseElementNavigator<IScopedNode>.Children(string? name) =>
+             childrenInternal(name);
     }
 }
+
+#nullable restore

src/Hl7.Fhir.Base/ElementModel/ScopedNodeExtensions.cs

@@ -136,7 +136,7 @@ public static string MakeAbsolute(this ScopedNode node, string reference) =>
             string? url = element switch
             {
                 { Value: string s } => s,
-                { InstanceType: FhirTypeConstants.REFERENCE } => element.ParseResourceReference()?.Reference,
+                { InstanceType: FhirTypeConstants.REFERENCE } => element.ParseResourceReference<ITypedElement>()?.Reference,
                 _ => null
             };