add reflectionHelper.GetPrivateProperty<T> (#231)

5 files changed, 192 insertions, 0 deletions

diff --git a/src/StardewModdingAPI/Framework/Reflection/PrivateProperty.cs b/src/StardewModdingAPI/Framework/Reflection/PrivateProperty.cs
new file mode 100644
index 00000000..08204b7e
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/Reflection/PrivateProperty.cs
@@ -0,0 +1,93 @@
+using System;
+using System.Reflection;
+
+namespace StardewModdingAPI.Framework.Reflection
+{
+    /// <summary>A private property obtained through reflection.</summary>
+    /// <typeparam name="TValue">The property value type.</typeparam>
+    internal class PrivateProperty<TValue> : IPrivateProperty<TValue>
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The type that has the field.</summary>
+        private readonly Type ParentType;
+
+        /// <summary>The object that has the instance field (if applicable).</summary>
+        private readonly object Parent;
+
+        /// <summary>The display name shown in error messages.</summary>
+        private string DisplayName => $"{this.ParentType.FullName}::{this.PropertyInfo.Name}";
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The reflection metadata.</summary>
+        public PropertyInfo PropertyInfo { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="parentType">The type that has the field.</param>
+        /// <param name="obj">The object that has the instance field (if applicable).</param>
+        /// <param name="property">The reflection metadata.</param>
+        /// <param name="isStatic">Whether the field is static.</param>
+        /// <exception cref="ArgumentNullException">The <paramref name="parentType"/> or <paramref name="property"/> is null.</exception>
+        /// <exception cref="ArgumentException">The <paramref name="obj"/> is null for a non-static field, or not null for a static field.</exception>
+        public PrivateProperty(Type parentType, object obj, PropertyInfo property, bool isStatic)
+        {
+            // validate
+            if (parentType == null)
+                throw new ArgumentNullException(nameof(parentType));
+            if (property == null)
+                throw new ArgumentNullException(nameof(property));
+            if (isStatic && obj != null)
+                throw new ArgumentException("A static property cannot have an object instance.");
+            if (!isStatic && obj == null)
+                throw new ArgumentException("A non-static property must have an object instance.");
+
+            // save
+            this.ParentType = parentType;
+            this.Parent = obj;
+            this.PropertyInfo = property;
+        }
+
+        /// <summary>Get the property value.</summary>
+        public TValue GetValue()
+        {
+            try
+            {
+                return (TValue)this.PropertyInfo.GetValue(this.Parent);
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidCastException($"Can't convert the private {this.DisplayName} property from {this.PropertyInfo.PropertyType.FullName} to {typeof(TValue).FullName}.");
+            }
+            catch (Exception ex)
+            {
+                throw new Exception($"Couldn't get the value of the private {this.DisplayName} property", ex);
+            }
+        }
+
+        /// <summary>Set the property value.</summary>
+        //// <param name="value">The value to set.</param>
+        public void SetValue(TValue value)
+        {
+            try
+            {
+                this.PropertyInfo.SetValue(this.Parent, value);
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidCastException($"Can't assign the private {this.DisplayName} property a {typeof(TValue).FullName} value, must be compatible with {this.PropertyInfo.PropertyType.FullName}.");
+            }
+            catch (Exception ex)
+            {
+                throw new Exception($"Couldn't set the value of the private {this.DisplayName} property", ex);
+            }
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/Reflection/ReflectionHelper.cs b/src/StardewModdingAPI/Framework/Reflection/ReflectionHelper.cs
index edf59b81..7a5789dc 100644
--- a/src/StardewModdingAPI/Framework/Reflection/ReflectionHelper.cs
+++ b/src/StardewModdingAPI/Framework/Reflection/ReflectionHelper.cs
@@ -59,6 +59,41 @@ namespace StardewModdingAPI.Framework.Reflection
         }
 
         /****
+        ** Properties
+        ****/
+        /// <summary>Get a private instance property.</summary>
+        /// <typeparam name="TValue">The property type.</typeparam>
+        /// <param name="obj">The object which has the property.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="required">Whether to throw an exception if the private property is not found.</param>
+        public IPrivateProperty<TValue> GetPrivateProperty<TValue>(object obj, string name, bool required = true)
+        {
+            // validate
+            if (obj == null)
+                throw new ArgumentNullException(nameof(obj), "Can't get a private instance property from a null object.");
+
+            // get property from hierarchy
+            IPrivateProperty<TValue> property = this.GetPropertyFromHierarchy<TValue>(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic);
+            if (required && property == null)
+                throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a private '{name}' instance property.");
+            return property;
+        }
+
+        /// <summary>Get a private static property.</summary>
+        /// <typeparam name="TValue">The property type.</typeparam>
+        /// <param name="type">The type which has the property.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="required">Whether to throw an exception if the private property is not found.</param>
+        public IPrivateProperty<TValue> GetPrivateProperty<TValue>(Type type, string name, bool required = true)
+        {
+            // get field from hierarchy
+            IPrivateProperty<TValue> property = this.GetPropertyFromHierarchy<TValue>(type, null, name, BindingFlags.NonPublic | BindingFlags.Static);
+            if (required && property == null)
+                throw new InvalidOperationException($"The {type.FullName} object doesn't have a private '{name}' static property.");
+            return property;
+        }
+
+        /****
         ** Field values
         ** (shorthand since this is the most common case)
         ****/
@@ -192,6 +227,28 @@ namespace StardewModdingAPI.Framework.Reflection
                 : null;
         }
 
+        /// <summary>Get a property from the type hierarchy.</summary>
+        /// <typeparam name="TValue">The expected property type.</typeparam>
+        /// <param name="type">The type which has the property.</param>
+        /// <param name="obj">The object which has the property.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="bindingFlags">The reflection binding which flags which indicates what type of property to find.</param>
+        private IPrivateProperty<TValue> GetPropertyFromHierarchy<TValue>(Type type, object obj, string name, BindingFlags bindingFlags)
+        {
+            bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
+            PropertyInfo property = this.GetCached<PropertyInfo>($"property::{isStatic}::{type.FullName}::{name}", () =>
+            {
+                PropertyInfo propertyInfo = null;
+                for (; type != null && propertyInfo == null; type = type.BaseType)
+                    propertyInfo = type.GetProperty(name, bindingFlags);
+                return propertyInfo;
+            });
+
+            return property != null
+                ? new PrivateProperty<TValue>(type, obj, property, isStatic)
+                : null;
+        }
+
         /// <summary>Get a method from the type hierarchy.</summary>
         /// <param name="type">The type which has the method.</param>
         /// <param name="obj">The object which has the method.</param>
diff --git a/src/StardewModdingAPI/IPrivateProperty.cs b/src/StardewModdingAPI/IPrivateProperty.cs
new file mode 100644
index 00000000..8d67fa7a
--- /dev/null
+++ b/src/StardewModdingAPI/IPrivateProperty.cs
@@ -0,0 +1,26 @@
+using System.Reflection;
+
+namespace StardewModdingAPI
+{
+    /// <summary>A private property obtained through reflection.</summary>
+    /// <typeparam name="TValue">The property value type.</typeparam>
+    public interface IPrivateProperty<TValue>
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The reflection metadata.</summary>
+        PropertyInfo PropertyInfo { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Get the property value.</summary>
+        TValue GetValue();
+
+        /// <summary>Set the property value.</summary>
+        //// <param name="value">The value to set.</param>
+        void SetValue(TValue value);
+    }
+}
\ No newline at end of file
diff --git a/src/StardewModdingAPI/IReflectionHelper.cs b/src/StardewModdingAPI/IReflectionHelper.cs
index 5d747eda..77943c6c 100644
--- a/src/StardewModdingAPI/IReflectionHelper.cs
+++ b/src/StardewModdingAPI/IReflectionHelper.cs
@@ -22,6 +22,20 @@ namespace StardewModdingAPI
         /// <param name="required">Whether to throw an exception if the private field is not found.</param>
         IPrivateField<TValue> GetPrivateField<TValue>(Type type, string name, bool required = true);
 
+        /// <summary>Get a private instance property.</summary>
+        /// <typeparam name="TValue">The property type.</typeparam>
+        /// <param name="obj">The object which has the property.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="required">Whether to throw an exception if the private property is not found.</param>
+        IPrivateProperty<TValue> GetPrivateProperty<TValue>(object obj, string name, bool required = true);
+
+        /// <summary>Get a private static property.</summary>
+        /// <typeparam name="TValue">The property type.</typeparam>
+        /// <param name="type">The type which has the property.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="required">Whether to throw an exception if the private property is not found.</param>
+        IPrivateProperty<TValue> GetPrivateProperty<TValue>(Type type, string name, bool required = true);
+
         /// <summary>Get the value of a private instance field.</summary>
         /// <typeparam name="TValue">The field type.</typeparam>
         /// <param name="obj">The object which has the field.</param>
diff --git a/src/StardewModdingAPI/StardewModdingAPI.csproj b/src/StardewModdingAPI/StardewModdingAPI.csproj
index aa8cad34..cecfc831 100644
--- a/src/StardewModdingAPI/StardewModdingAPI.csproj
+++ b/src/StardewModdingAPI/StardewModdingAPI.csproj
@@ -149,6 +149,7 @@
     <Compile Include="Events\GraphicsEvents.cs" />
     <Compile Include="Framework\AssemblyDefinitionResolver.cs" />
     <Compile Include="Framework\AssemblyParseResult.cs" />
+    <Compile Include="Framework\Reflection\PrivateProperty.cs" />
     <Compile Include="Framework\Serialisation\SemanticVersionConverter.cs" />
     <Compile Include="IModRegistry.cs" />
     <Compile Include="Events\LocationEvents.cs" />
@@ -170,6 +171,7 @@
     <Compile Include="IMod.cs" />
     <Compile Include="IModHelper.cs" />
     <Compile Include="Framework\LogFileManager.cs" />
+    <Compile Include="IPrivateProperty.cs" />
     <Compile Include="ISemanticVersion.cs" />
     <Compile Include="LogLevel.cs" />
     <Compile Include="Framework\ModRegistry.cs" />