add load conflict resolution option (#766)

3 files changed, 17 insertions, 8 deletions

diff --git a/src/SMAPI/Framework/Content/AssetLoadOperation.cs b/src/SMAPI/Framework/Content/AssetLoadOperation.cs
index 29bf1518..36baf1aa 100644
--- a/src/SMAPI/Framework/Content/AssetLoadOperation.cs
+++ b/src/SMAPI/Framework/Content/AssetLoadOperation.cs
@@ -14,6 +14,9 @@ namespace StardewModdingAPI.Framework.Content
         /// <summary>The content pack on whose behalf the asset is being loaded, if any.</summary>
         public IModMetadata OnBehalfOf { get; }
 
+        /// <summary>Whether to allow skipping this operation to resolve a load conflict.</summary>
+        public bool AllowSkipOnConflict { get; }
+
         /// <summary>Load the initial value for an asset.</summary>
         public Func<IAssetInfo, object> GetData { get; }
 
@@ -23,11 +26,13 @@ namespace StardewModdingAPI.Framework.Content
         *********/
         /// <summary>Construct an instance.</summary>
         /// <param name="mod">The mod applying the edit.</param>
+        /// <param name="allowSkipOnConflict">Whether to allow skipping this operation to resolve a load conflict.</param>
         /// <param name="onBehalfOf">The content pack on whose behalf the asset is being loaded, if any.</param>
         /// <param name="getData">Load the initial value for an asset.</param>
-        public AssetLoadOperation(IModMetadata mod, IModMetadata onBehalfOf, Func<IAssetInfo, object> getData)
+        public AssetLoadOperation(IModMetadata mod, bool allowSkipOnConflict, IModMetadata onBehalfOf, Func<IAssetInfo, object> getData)
         {
             this.Mod = mod;
+            this.AllowSkipOnConflict = allowSkipOnConflict;
             this.OnBehalfOf = onBehalfOf;
             this.GetData = getData;
         }
diff --git a/src/SMAPI/Framework/ContentCoordinator.cs b/src/SMAPI/Framework/ContentCoordinator.cs
index 3b304f0d..43cebcbe 100644
--- a/src/SMAPI/Framework/ContentCoordinator.cs
+++ b/src/SMAPI/Framework/ContentCoordinator.cs
@@ -608,6 +608,7 @@ namespace StardewModdingAPI.Framework
                     {
                         new AssetLoadOperation(
                             mod: loader.Mod,
+                            allowSkipOnConflict: false,
                             onBehalfOf: null,
                             getData: assetInfo => loader.Data.Load<T>(assetInfo)
                         )
diff --git a/src/SMAPI/Framework/ContentManagers/GameContentManager.cs b/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
index 1d9c8b4c..b3e98648 100644
--- a/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
+++ b/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
@@ -80,7 +80,7 @@ namespace StardewModdingAPI.Framework.ContentManagers
             IAssetInfo info = new AssetInfo(locale, assetName, typeof(object), this.AssertAndNormalizeAssetName);
             AssetLoadOperation[] loaders = this.GetLoaders<object>(info).ToArray();
 
-            if (!this.AssertMaxOneLoader(info, loaders, out string error))
+            if (!this.AssertMaxOneRequiredLoader(info, loaders, out string error))
                 this.Monitor.Log(error, LogLevel.Warn);
 
             return loaders.Length == 1;
@@ -277,13 +277,15 @@ namespace StardewModdingAPI.Framework.ContentManagers
             {
                 AssetLoadOperation[] loaders = this.GetLoaders<T>(info).ToArray();
 
-                if (!this.AssertMaxOneLoader(info, loaders, out string error))
+                if (!this.AssertMaxOneRequiredLoader(info, loaders, out string error))
                 {
                     this.Monitor.Log(error, LogLevel.Warn);
                     return null;
                 }
 
-                loader = loaders.FirstOrDefault();
+                loader =
+                    loaders.FirstOrDefault(p => !p.AllowSkipOnConflict)
+                    ?? loaders.FirstOrDefault();
             }
 
             // no loader found
@@ -392,20 +394,21 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <param name="loaders">The asset loaders to apply.</param>
         /// <param name="error">The error message to show to the user, if the method returns false.</param>
         /// <returns>Returns true if only one loader will apply, else false.</returns>
-        private bool AssertMaxOneLoader(IAssetInfo info, AssetLoadOperation[] loaders, out string error)
+        private bool AssertMaxOneRequiredLoader(IAssetInfo info, AssetLoadOperation[] loaders, out string error)
         {
-            if (loaders.Length <= 1)
+            AssetLoadOperation[] required = loaders.Where(p => !p.AllowSkipOnConflict).ToArray();
+            if (required.Length <= 1)
             {
                 error = null;
                 return true;
             }
 
-            string[] loaderNames = loaders
+            string[] loaderNames = required
                 .Select(p => p.Mod.DisplayName + this.GetOnBehalfOfLabel(p.OnBehalfOf))
                 .Distinct()
                 .ToArray();
             string errorPhrase = loaderNames.Length > 1
-                ? $"Multiple mods want to provide '{info.Name}' asset: {string.Join(", ", loaderNames)}"
+                ? $"Multiple mods want to provide the '{info.Name}' asset: {string.Join(", ", loaderNames)}"
                 : $"The '{loaderNames[0]}' mod wants to provide the '{info.Name}' asset multiple times";
 
             error = $"{errorPhrase}. An asset can't be loaded multiple times, so SMAPI will use the default asset instead. Uninstall one of the mods to fix this. (Message for modders: you should usually use {typeof(IAssetEditor)} instead to avoid conflicts.)";