Added Schema Coordinates

src/HotChocolate/Core/src/Abstractions/Properties/AbstractionResources.resx

@@ -198,4 +198,10 @@
   <data name="ThrowHelper_TryRewriteNullability_InvalidNullabilityStructure" xml:space="preserve">
     <value>The nullability modifier does not match the field type structure.</value>
   </data>
+  <data name="ThrowHelper_SchemaCoordinate_ArgumentNameCannotBeSetWithoutMemberName" xml:space="preserve">
+    <value>A argument name without a member name is only allowed on directive coordinates.</value>
+  </data>
+  <data name="ThrowHelper_SchemaCoordinate_MemberNameCannotBeSetOnADirectiveCoordinate" xml:space="preserve">
+    <value>A directive cannot contain a member name.</value>
+  </data>
 </root>

src/HotChocolate/Core/src/Abstractions/SchemaCoordinate.cs

@@ -0,0 +1,170 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using HotChocolate.Language;
+using static HotChocolate.Properties.AbstractionResources;
+
+namespace HotChocolate;
+
+/// <summary>
+/// A <see cref="SchemaCoordinate"/> is a human readable string that uniquely identifies a
+/// schema element within a GraphQL Schema.
+/// A schema element is a specific instance of a named type, field, input field, enum value,
+/// field argument, directive, or directive argument.
+/// A <see cref="SchemaCoordinate"/> is always unique. Each schema element may be referenced
+/// by exactly one possible schema coordinate.
+///
+/// A <see cref="SchemaCoordinate"/> may refer to either a defined or built-in schema element.
+/// For example, `String` and `@deprecated(reason:)` are both valid schema coordinates which refer
+/// to built-in schema elements. However it must not refer to a meta-field.
+/// For example, `Business.__typename` is <b>not</b> a valid schema coordinate.
+///
+/// SchemaCoordinate :
+///  - Name
+///  - Name . Name
+///  - Name . Name ( Name : )
+///  - @ Name
+///  - @ Name ( Name : )
+/// </summary>
+public readonly struct SchemaCoordinate
+{
+    /// <summary>
+    /// Creates a new instance of <see cref="SchemaCoordinate"/>
+    /// </summary>
+    /// <exception cref="ArgumentNullException">
+    /// The <paramref name="name"/> is <c>null</c> or <see cref="String.Empty" />.
+    /// </exception>
+    /// <exception cref="ArgumentException">
+    /// - A directive cannot contain a <paramref name="memberName"/>.
+    /// - A <paramref name="argumentName"/>. without a <paramref name="memberName"/> is only allowed 
+    /// on directive coordinates.
+    /// </exception>
+    public SchemaCoordinate(
+        NameString name,
+        NameString? memberName = null,
+        NameString? argumentName = null,
+        bool ofDirective = false)
+    {
+        memberName?.EnsureNotEmpty(nameof(memberName));
+        argumentName?.EnsureNotEmpty(nameof(argumentName));
+
+        if (ofDirective && memberName is not null)
+        {
+            throw new ArgumentException(
+                ThrowHelper_SchemaCoordinate_MemberNameCannotBeSetOnADirectiveCoordinate,
+                nameof(memberName));
+        }
+
+        if (!ofDirective && memberName is null && argumentName is not null)
+        {
+            throw new ArgumentException(
+                ThrowHelper_SchemaCoordinate_ArgumentNameCannotBeSetWithoutMemberName, 
+                nameof(argumentName));
+        }
+
+        Name = name.EnsureNotEmpty(nameof(name));
+        MemberName = memberName;
+        ArgumentName = argumentName;
+        OfDirective = ofDirective;
+    }
+
+    /// <summary>
+    /// Specifies if this <see cref="SchemaCoordinateNode"/> is a coordinate of a directive.
+    /// </summary>
+    public bool OfDirective { get; }
+
+    /// <summary>
+    /// The name of the referenced <see cref="INamedSyntaxNode"/>
+    /// </summary>
+    public NameString Name { get; }
+
+    /// <summary>
+    /// The optional name of the referenced field or enum value
+    /// </summary>
+    public NameString? MemberName { get; }
+
+    /// <summary>
+    /// The optional name of the referenced argument
+    /// </summary>
+    public NameString? ArgumentName { get; }
+
+    /// <summary>
+    /// Gets the syntax representation of this <see cref="SchemaCoordinate"/>.
+    /// </summary>
+    public SchemaCoordinateNode ToSyntax()
+    {
+        NameNode? memberName = MemberName is null ? null : new(MemberName.Value);
+        NameNode? argumentName = ArgumentName is null ? null : new(ArgumentName.Value);
+
+        return new(null, OfDirective, new(Name.Value), memberName, argumentName);
+    }
+
+    /// <summary>
+    /// Gets the string representation of this <see cref="SchemaCoordinate"/>.
+    /// </summary>
+    public override string ToString() => ToSyntax().ToString();
+
+    /// <summary>
+    /// Tries to parse a <see cref="SchemaCoordinate"/> from a <see cref="String"/>.
+    /// </summary>
+    /// <param name="s">The string that may represent a <see cref="SchemaCoordinate"/>.</param>
+    /// <param name="coordinate">
+    /// If the string <paramref name="s"/> represented a valid schema coordinate string this 
+    /// will be the parsed schema coordinate.
+    /// </param>
+    /// <returns>
+    /// <c>true</c> if the string was a valid representation of a schema coordinate.
+    /// </returns>
+    public static bool TryParse(
+        string s,
+        [NotNullWhen(true)] out SchemaCoordinate? coordinate)
+    {
+        if (string.IsNullOrEmpty(s))
+        {
+            coordinate = null;
+            return false;
+        }
+
+        try
+        {
+            coordinate = Parse(s);
+            return true;
+        }
+        catch (SyntaxException)
+        {
+            coordinate = null;
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Parses a schema coordinate string representation.
+    /// </summary>
+    /// <param name="s">The schema coordinate string representation.</param>
+    /// <returns>
+    /// Returns the parses schema coordinate.
+    /// </returns>
+    public static SchemaCoordinate Parse(string s)
+        => FromSyntax(Utf8GraphQLParser.Syntax.ParseSchemaCoordinate(s));
+
+    /// <summary>
+    /// Creates a <see cref="SchemaCoordinate"/> from a <see cref="SchemaCoordinateNode"/>.
+    /// </summary>
+    /// <param name="node">
+    /// The syntax node.
+    /// </param>
+    /// <returns>
+    /// Returns the <see cref="SchemaCoordinate"/> instance.
+    /// </returns>
+    public static SchemaCoordinate FromSyntax(SchemaCoordinateNode node)
+    {
+        NameString? memberName = node.MemberName is null
+            ? null
+            : (NameString?)node.MemberName.Value;
+
+        NameString? argumentName = node.ArgumentName is null
+            ? null
+            : (NameString?)node.ArgumentName.Value;
+
+        return new(node.Name.Value, memberName, argumentName, node.OfDirective);
+    }
+}