enable nullable annotations in SMAPI where no logic changes are needed (#837)

79 files changed, 369 insertions, 466 deletions

diff --git a/src/SMAPI/Framework/Command.cs b/src/SMAPI/Framework/Command.cs
index 776ba238..dca1dd09 100644
--- a/src/SMAPI/Framework/Command.cs
+++ b/src/SMAPI/Framework/Command.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 
 namespace StardewModdingAPI.Framework
@@ -11,7 +9,7 @@ namespace StardewModdingAPI.Framework
         ** Accessor
         *********/
         /// <summary>The mod that registered the command (or <c>null</c> if registered by SMAPI).</summary>
-        public IModMetadata Mod { get; }
+        public IModMetadata? Mod { get; }
 
         /// <summary>The command name, which the user must type to trigger it.</summary>
         public string Name { get; }
@@ -31,7 +29,7 @@ namespace StardewModdingAPI.Framework
         /// <param name="name">The command name, which the user must type to trigger it.</param>
         /// <param name="documentation">The human-readable documentation shown when the player runs the built-in 'help' command.</param>
         /// <param name="callback">The method to invoke when the command is triggered. This method is passed the command name and arguments submitted by the user.</param>
-        public Command(IModMetadata mod, string name, string documentation, Action<string, string[]> callback)
+        public Command(IModMetadata? mod, string name, string documentation, Action<string, string[]> callback)
         {
             this.Mod = mod;
             this.Name = name;
diff --git a/src/SMAPI/Framework/Commands/HarmonySummaryCommand.cs b/src/SMAPI/Framework/Commands/HarmonySummaryCommand.cs
index fcfa928e..6dc6f131 100644
--- a/src/SMAPI/Framework/Commands/HarmonySummaryCommand.cs
+++ b/src/SMAPI/Framework/Commands/HarmonySummaryCommand.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -73,9 +71,9 @@ namespace StardewModdingAPI.Framework.Commands
         private IEnumerable<SearchResult> FilterPatches(string[] searchTerms)
         {
             bool hasSearch = searchTerms.Any();
-            bool IsMatch(string target) => !hasSearch || searchTerms.Any(search => target != null && target.IndexOf(search, StringComparison.OrdinalIgnoreCase) > -1);
+            bool IsMatch(string? target) => !hasSearch || searchTerms.Any(search => target != null && target.IndexOf(search, StringComparison.OrdinalIgnoreCase) > -1);
 
-            foreach (var patch in this.GetAllPatches())
+            foreach (SearchResult patch in this.GetAllPatches())
             {
                 // matches entire patch
                 if (IsMatch(patch.MethodDescription))
@@ -85,10 +83,10 @@ namespace StardewModdingAPI.Framework.Commands
                 }
 
                 // matches individual patchers
-                foreach (var pair in patch.PatchTypesByOwner.ToArray())
+                foreach ((string patcherId, ISet<PatchType> patchTypes) in patch.PatchTypesByOwner.ToArray())
                 {
-                    if (!IsMatch(pair.Key) && !pair.Value.Any(type => IsMatch(type.ToString())))
-                        patch.PatchTypesByOwner.Remove(pair.Key);
+                    if (!IsMatch(patcherId) && !patchTypes.Any(type => IsMatch(type.ToString())))
+                        patch.PatchTypesByOwner.Remove(patcherId);
                 }
 
                 if (patch.PatchTypesByOwner.Any())
@@ -114,13 +112,13 @@ namespace StardewModdingAPI.Framework.Commands
 
                 // get patch types by owner
                 var typesByOwner = new Dictionary<string, ISet<PatchType>>();
-                foreach (var group in patchGroups)
+                foreach ((PatchType type, IReadOnlyCollection<Patch> patches) in patchGroups)
                 {
-                    foreach (var patch in group.Value)
+                    foreach (Patch patch in patches)
                     {
-                        if (!typesByOwner.TryGetValue(patch.owner, out ISet<PatchType> patchTypes))
+                        if (!typesByOwner.TryGetValue(patch.owner, out ISet<PatchType>? patchTypes))
                             typesByOwner[patch.owner] = patchTypes = new HashSet<PatchType>();
-                        patchTypes.Add(group.Key);
+                        patchTypes.Add(type);
                     }
                 }
 
diff --git a/src/SMAPI/Framework/Content/AssetData.cs b/src/SMAPI/Framework/Content/AssetData.cs
index be4a7ce6..0367e999 100644
--- a/src/SMAPI/Framework/Content/AssetData.cs
+++ b/src/SMAPI/Framework/Content/AssetData.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 
 namespace StardewModdingAPI.Framework.Content
@@ -7,12 +5,13 @@ namespace StardewModdingAPI.Framework.Content
     /// <summary>Base implementation for a content helper which encapsulates access and changes to content being read from a data file.</summary>
     /// <typeparam name="TValue">The interface value type.</typeparam>
     internal class AssetData<TValue> : AssetInfo, IAssetData<TValue>
+        where TValue : notnull
     {
         /*********
         ** Fields
         *********/
         /// <summary>A callback to invoke when the data is replaced (if any).</summary>
-        private readonly Action<TValue> OnDataReplaced;
+        private readonly Action<TValue>? OnDataReplaced;
 
 
         /*********
@@ -31,7 +30,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="data">The content data being read.</param>
         /// <param name="getNormalizedPath">Normalizes an asset key to match the cache key.</param>
         /// <param name="onDataReplaced">A callback to invoke when the data is replaced (if any).</param>
-        public AssetData(string locale, IAssetName assetName, TValue data, Func<string, string> getNormalizedPath, Action<TValue> onDataReplaced)
+        public AssetData(string? locale, IAssetName assetName, TValue data, Func<string, string> getNormalizedPath, Action<TValue>? onDataReplaced)
             : base(locale, assetName, data.GetType(), getNormalizedPath)
         {
             this.Data = data;
diff --git a/src/SMAPI/Framework/Content/AssetDataForDictionary.cs b/src/SMAPI/Framework/Content/AssetDataForDictionary.cs
index 06dbe259..d9bfa7bf 100644
--- a/src/SMAPI/Framework/Content/AssetDataForDictionary.cs
+++ b/src/SMAPI/Framework/Content/AssetDataForDictionary.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 
@@ -17,7 +15,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="data">The content data being read.</param>
         /// <param name="getNormalizedPath">Normalizes an asset key to match the cache key.</param>
         /// <param name="onDataReplaced">A callback to invoke when the data is replaced (if any).</param>
-        public AssetDataForDictionary(string locale, IAssetName assetName, IDictionary<TKey, TValue> data, Func<string, string> getNormalizedPath, Action<IDictionary<TKey, TValue>> onDataReplaced)
+        public AssetDataForDictionary(string? locale, IAssetName assetName, IDictionary<TKey, TValue> data, Func<string, string> getNormalizedPath, Action<IDictionary<TKey, TValue>> onDataReplaced)
             : base(locale, assetName, data, getNormalizedPath, onDataReplaced) { }
     }
 }
diff --git a/src/SMAPI/Framework/Content/AssetDataForImage.cs b/src/SMAPI/Framework/Content/AssetDataForImage.cs
index 8e59cd27..97729c95 100644
--- a/src/SMAPI/Framework/Content/AssetDataForImage.cs
+++ b/src/SMAPI/Framework/Content/AssetDataForImage.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
@@ -27,7 +25,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="data">The content data being read.</param>
         /// <param name="getNormalizedPath">Normalizes an asset key to match the cache key.</param>
         /// <param name="onDataReplaced">A callback to invoke when the data is replaced (if any).</param>
-        public AssetDataForImage(string locale, IAssetName assetName, Texture2D data, Func<string, string> getNormalizedPath, Action<Texture2D> onDataReplaced)
+        public AssetDataForImage(string? locale, IAssetName assetName, Texture2D data, Func<string, string> getNormalizedPath, Action<Texture2D> onDataReplaced)
             : base(locale, assetName, data, getNormalizedPath, onDataReplaced) { }
 
         /// <inheritdoc />
diff --git a/src/SMAPI/Framework/Content/AssetDataForObject.cs b/src/SMAPI/Framework/Content/AssetDataForObject.cs
index bb3966b9..e508ca30 100644
--- a/src/SMAPI/Framework/Content/AssetDataForObject.cs
+++ b/src/SMAPI/Framework/Content/AssetDataForObject.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using Microsoft.Xna.Framework.Graphics;
@@ -27,7 +25,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="data">The content data being read.</param>
         /// <param name="getNormalizedPath">Normalizes an asset key to match the cache key.</param>
         /// <param name="reflection">Simplifies access to private code.</param>
-        public AssetDataForObject(string locale, IAssetName assetName, object data, Func<string, string> getNormalizedPath, Reflector reflection)
+        public AssetDataForObject(string? locale, IAssetName assetName, object data, Func<string, string> getNormalizedPath, Reflector reflection)
             : base(locale, assetName, data, getNormalizedPath, onDataReplaced: null)
         {
             this.Reflection = reflection;
diff --git a/src/SMAPI/Framework/Content/AssetEditOperation.cs b/src/SMAPI/Framework/Content/AssetEditOperation.cs
index 1b7d0c93..464948b0 100644
--- a/src/SMAPI/Framework/Content/AssetEditOperation.cs
+++ b/src/SMAPI/Framework/Content/AssetEditOperation.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using StardewModdingAPI.Events;
 
@@ -18,7 +16,7 @@ namespace StardewModdingAPI.Framework.Content
         public AssetEditPriority Priority { get; }
 
         /// <summary>The content pack on whose behalf the edit is being applied, if any.</summary>
-        public IModMetadata OnBehalfOf { get; }
+        public IModMetadata? OnBehalfOf { get; }
 
         /// <summary>Apply the edit to an asset.</summary>
         public Action<IAssetData> ApplyEdit { get; }
@@ -32,7 +30,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="priority">If there are multiple edits that apply to the same asset, the priority with which this one should be applied.</param>
         /// <param name="onBehalfOf">The content pack on whose behalf the edit is being applied, if any.</param>
         /// <param name="applyEdit">Apply the edit to an asset.</param>
-        public AssetEditOperation(IModMetadata mod, AssetEditPriority priority, IModMetadata onBehalfOf, Action<IAssetData> applyEdit)
+        public AssetEditOperation(IModMetadata mod, AssetEditPriority priority, IModMetadata? onBehalfOf, Action<IAssetData> applyEdit)
         {
             this.Mod = mod;
             this.Priority = priority;
diff --git a/src/SMAPI/Framework/Content/AssetInfo.cs b/src/SMAPI/Framework/Content/AssetInfo.cs
index 51dcc61f..0f0e9bf3 100644
--- a/src/SMAPI/Framework/Content/AssetInfo.cs
+++ b/src/SMAPI/Framework/Content/AssetInfo.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using Microsoft.Xna.Framework.Graphics;
@@ -19,7 +17,7 @@ namespace StardewModdingAPI.Framework.Content
         ** Accessors
         *********/
         /// <inheritdoc />
-        public string Locale { get; }
+        public string? Locale { get; }
 
         /// <inheritdoc />
         public IAssetName Name { get; }
@@ -28,7 +26,7 @@ namespace StardewModdingAPI.Framework.Content
         public IAssetName NameWithoutLocale { get; }
 
         /// <inheritdoc />
-        [Obsolete($"Use {nameof(Name)} or {nameof(NameWithoutLocale)} instead. This property will be removed in SMAPI 4.0.0.")]
+        [Obsolete($"Use {nameof(AssetInfo.Name)} or {nameof(AssetInfo.NameWithoutLocale)} instead. This property will be removed in SMAPI 4.0.0.")]
         public string AssetName
         {
             get
@@ -56,7 +54,7 @@ namespace StardewModdingAPI.Framework.Content
         /// <param name="assetName">The asset name being read.</param>
         /// <param name="type">The content type being read.</param>
         /// <param name="getNormalizedPath">Normalizes an asset key to match the cache key.</param>
-        public AssetInfo(string locale, IAssetName assetName, Type type, Func<string, string> getNormalizedPath)
+        public AssetInfo(string? locale, IAssetName assetName, Type type, Func<string, string> getNormalizedPath)
         {
             this.Locale = locale;
             this.Name = assetName;
@@ -66,7 +64,7 @@ namespace StardewModdingAPI.Framework.Content
         }
 
         /// <inheritdoc />
-        [Obsolete($"Use {nameof(Name)}.{nameof(IAssetName.IsEquivalentTo)} or {nameof(NameWithoutLocale)}.{nameof(IAssetName.IsEquivalentTo)} instead. This method will be removed in SMAPI 4.0.0.")]
+        [Obsolete($"Use {nameof(Name)}.{nameof(IAssetName.IsEquivalentTo)} or {nameof(AssetInfo.NameWithoutLocale)}.{nameof(IAssetName.IsEquivalentTo)} instead. This method will be removed in SMAPI 4.0.0.")]
         public bool AssetNameEquals(string path)
         {
             SCore.DeprecationManager.Warn(
@@ -106,7 +104,7 @@ namespace StardewModdingAPI.Framework.Content
                 return "string";
 
             // default
-