C#: Expose attribute properties and add documentation

- Exposes the properties of C# attribute so they can be accessed from
reflection, renaming them to PascalCase to follow .NET conventions.
- Added some documentation to the newly exposed members.
- Made attribute properties readonly to avoid giving the impression that
they could be modified.

7 files changed, 68 insertions, 24 deletions

diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/AssemblyHasScriptsAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/AssemblyHasScriptsAttribute.cs
index b7d633517a..acdae83d2e 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/AssemblyHasScriptsAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/AssemblyHasScriptsAttribute.cs
@@ -1,20 +1,32 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 
 #nullable enable
 
 namespace Godot
 {
     /// <summary>
-    /// An attribute that determines if an assembly has scripts. If so, what types of scripts the assembly has.
+    /// Attribute that determines that the assembly contains Godot scripts and, optionally, the
+    /// collection of types that implement scripts; otherwise, retrieving the types requires lookup.
     /// </summary>
     [AttributeUsage(AttributeTargets.Assembly)]
     public class AssemblyHasScriptsAttribute : Attribute
     {
+        /// <summary>
+        /// If the Godot scripts contained in the assembly require lookup
+        /// and can't rely on <see cref="ScriptTypes"/>.
+        /// </summary>
+        [MemberNotNullWhen(false, nameof(ScriptTypes))]
         public bool RequiresLookup { get; }
+
+        /// <summary>
+        /// The collection of types that implement a Godot script.
+        /// </summary>
         public Type[]? ScriptTypes { get; }
 
         /// <summary>
-        /// Constructs a new AssemblyHasScriptsAttribute instance.
+        /// Constructs a new AssemblyHasScriptsAttribute instance
+        /// that requires lookup to get the Godot scripts.
         /// </summary>
         public AssemblyHasScriptsAttribute()
         {
@@ -23,9 +35,10 @@ namespace Godot
         }
 
         /// <summary>
-        /// Constructs a new AssemblyHasScriptsAttribute instance.
+        /// Constructs a new AssemblyHasScriptsAttribute instance
+        /// that includes the Godot script types and requires no lookup.
         /// </summary>
-        /// <param name="scriptTypes">The specified type(s) of scripts.</param>
+        /// <param name="scriptTypes">The collection of types that implement a Godot script.</param>
         public AssemblyHasScriptsAttribute(Type[] scriptTypes)
         {
             RequiresLookup = false;
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportAttribute.cs
index 3d204bdf9f..a48d79091f 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportAttribute.cs
@@ -3,23 +3,30 @@ using System;
 namespace Godot
 {
     /// <summary>
-    /// An attribute used to export objects.
+    /// Exports the annotated member as a property of the Godot Object.
     /// </summary>
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
     public sealed class ExportAttribute : Attribute
     {
-        private PropertyHint hint;
-        private string hintString;
+        /// <summary>
+        /// Optional hint that determines how the property should be handled by the editor.
+        /// </summary>
+        public PropertyHint Hint { get; }
+
+        /// <summary>
+        /// Optional string that can contain additional metadata for the <see cref="Hint"/>.
+        /// </summary>
+        public string HintString { get; }
 
         /// <summary>
         /// Constructs a new ExportAttribute Instance.
         /// </summary>
-        /// <param name="hint">A hint to the exported object.</param>
-        /// <param name="hintString">A string representing the exported object.</param>
+        /// <param name="hint">The hint for the exported property.</param>
+        /// <param name="hintString">A string that may contain additional metadata for the hint.</param>
         public ExportAttribute(PropertyHint hint = PropertyHint.None, string hintString = "")
         {
-            this.hint = hint;
-            this.hintString = hintString;
+            Hint = hint;
+            HintString = hintString;
         }
     }
 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportCategoryAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportCategoryAttribute.cs
index 101e56f8d3..2ae55acd3e 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportCategoryAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportCategoryAttribute.cs
@@ -8,7 +8,10 @@ namespace Godot
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
     public sealed class ExportCategoryAttribute : Attribute
     {
-        private string name;
+        /// <summary>
+        /// Name of the category.
+        /// </summary>
+        public string Name { get; }
 
         /// <summary>
         /// Define a new category for the following exported properties.
@@ -16,7 +19,7 @@ namespace Godot
         /// <param name="name">The name of the category.</param>
         public ExportCategoryAttribute(string name)
         {
-            this.name = name;
+            Name = name;
         }
     }
 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportGroupAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportGroupAttribute.cs
index 3bd532cec1..82bd446640 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportGroupAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportGroupAttribute.cs
@@ -1,5 +1,7 @@
 using System;
 
+#nullable enable
+
 namespace Godot
 {
     /// <summary>
@@ -8,8 +10,15 @@ namespace Godot
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
     public sealed class ExportGroupAttribute : Attribute
     {
-        private string name;
-        private string prefix;
+        /// <summary>
+        /// Name of the group.
+        /// </summary>
+        public string Name { get; }
+
+        /// <summary>
+        /// If provided, the prefix that all properties must have to be considered part of the group.
+        /// </summary>
+        public string? Prefix { get; }
 
         /// <summary>
         /// Define a new group for the following exported properties.
@@ -18,8 +27,8 @@ namespace Godot
         /// <param name="prefix">If provided, the group would make group to only consider properties that have this prefix.</param>
         public ExportGroupAttribute(string name, string prefix = "")
         {
-            this.name = name;
-            this.prefix = prefix;
+            Name = name;
+            Prefix = prefix;
         }
     }
 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportSubgroupAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportSubgroupAttribute.cs
index 2ae6eb0b68..3282b466f6 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportSubgroupAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ExportSubgroupAttribute.cs
@@ -1,5 +1,7 @@
 using System;
 
+#nullable enable
+
 namespace Godot
 {
     /// <summary>
@@ -8,8 +10,15 @@ namespace Godot
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
     public sealed class ExportSubgroupAttribute : Attribute
     {
-        private string name;
-        private string prefix;
+        /// <summary>
+        /// Name of the subgroup.
+        /// </summary>
+        public string Name { get; }
+
+        /// <summary>
+        /// If provided, the prefix that all properties must have to be considered part of the subgroup.
+        /// </summary>
+        public string? Prefix { get; }
 
         /// <summary>
         /// Define a new subgroup for the following exported properties. This helps to organize properties in the Inspector dock.
@@ -18,8 +27,8 @@ namespace Godot
         /// <param name="prefix">If provided, the subgroup would make group to only consider properties that have this prefix.</param>
         public ExportSubgroupAttribute(string name, string prefix = "")
         {
-            this.name = name;
-            this.prefix = prefix;
+            Name = name;
+            Prefix = prefix;
         }
     }
 }
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/RPCAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/RPCAttribute.cs
index fb37838ffa..afee926464 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/RPCAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/RPCAttribute.cs
@@ -19,17 +19,17 @@ namespace Godot
         /// <summary>
         /// If the method will also be called locally; otherwise, it is only called remotely.
         /// </summary>
-        public bool CallLocal { get; set; } = false;
+        public bool CallLocal { get; init; } = false;
 
         /// <summary>
         /// Transfer mode for the annotated method.
         /// </summary>
-        public MultiplayerPeer.TransferModeEnum TransferMode { get; set; } = MultiplayerPeer.TransferModeEnum.Reliable;
+        public MultiplayerPeer.TransferModeEnum TransferMode { get; init; } = MultiplayerPeer.TransferModeEnum.Reliable;
 
         /// <summary>
         /// Transfer channel for the annotated mode.
         /// </summary>
-        public int TransferChannel { get; set; } = 0;
+        public int TransferChannel { get; init; } = 0;
 
         /// <summary>
         /// Constructs a <see cref="RPCAttribute"/> instance.
diff --git a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ScriptPathAttribute.cs b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ScriptPathAttribute.cs
index 2c8a53ae1c..f05bcdac38 100644
--- a/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ScriptPathAttribute.cs
+++ b/modules/mono/glue/GodotSharp/GodotSharp/Core/Attributes/ScriptPathAttribute.cs
@@ -8,6 +8,9 @@ namespace Godot
     [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
     public class ScriptPathAttribute : Attribute
     {
+        /// <summary>
+        /// File path to the script.
+        /// </summary>
         public string Path { get; }
 
         /// <summary>