Magic the magic happen

Dalamud/Plugin/Internal/Exceptions/DuplicatePluginException.cs

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+namespace Dalamud.Plugin.Internal.Exceptions
+{
+    /// <summary>
+    /// This exception that is thrown when a plugin is instructed to load while another plugin with the same
+    /// assembly name is already present and loaded.
+    /// </summary>
+    internal class DuplicatePluginException : PluginException
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DuplicatePluginException"/> class.
+        /// </summary>
+        /// <param name="assemblyName">Name of the conflicting assembly.</param>
+        public DuplicatePluginException(string assemblyName)
+        {
+            this.AssemblyName = assemblyName;
+        }
+
+        /// <summary>
+        /// Gets the name of the conflicting assembly.
+        /// </summary>
+        public string AssemblyName { get; init; }
+
+        /// <inheritdoc/>
+        public override string Message => $"A plugin with the same assembly name of {this.AssemblyName} is already loaded";
+    }
+}

Dalamud/Plugin/Internal/Exceptions/InvalidPluginException.cs

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+using System;
+using System.IO;
+
+namespace Dalamud.Plugin.Internal.Exceptions
+{
+    /// <summary>
+    /// This exception represents a file that does not implement IDalamudPlugin.
+    /// </summary>
+    internal class InvalidPluginException : PluginException
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="InvalidPluginException"/> class.
+        /// </summary>
+        /// <param name="dllFile">The invalid file.</param>
+        public InvalidPluginException(FileInfo dllFile)
+        {
+            this.DllFile = dllFile;
+        }
+
+        /// <summary>
+        /// Gets the invalid file.
+        /// </summary>
+        public FileInfo DllFile { get; init; }
+    }
+}

Dalamud/Plugin/Internal/Exceptions/InvalidPluginOperationException.cs

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+using System;
+
+namespace Dalamud.Plugin.Internal.Exceptions
+{
+    /// <summary>
+    /// This represents an invalid plugin operation.
+    /// </summary>
+    internal class InvalidPluginOperationException : PluginException
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="InvalidPluginOperationException"/> class.
+        /// </summary>
+        /// <param name="message">The message describing the invalid operation.</param>
+        public InvalidPluginOperationException(string message)
+        {
+            this.Message = message;
+        }
+
+        /// <summary>
+        /// Gets the message describing the invalid operation.
+        /// </summary>
+        public override string Message { get; }
+    }
+}

Dalamud/Plugin/Internal/Exceptions/PluginException.cs

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+using System;
+
+namespace Dalamud.Plugin.Internal.Exceptions
+{
+    /// <summary>
+    /// This represents the base Dalamud plugin exception.
+    /// </summary>
+    internal abstract class PluginException : Exception
+    {
+    }
+}