enable nullable annotations in the rest of SMAPI core (#837)

3 files changed, 15 insertions, 17 deletions

diff --git a/src/SMAPI/Framework/StateTracking/FieldWatchers/ComparableWatcher.cs b/src/SMAPI/Framework/StateTracking/FieldWatchers/ComparableWatcher.cs
index 4f94294c..5f76fe0a 100644
--- a/src/SMAPI/Framework/StateTracking/FieldWatchers/ComparableWatcher.cs
+++ b/src/SMAPI/Framework/StateTracking/FieldWatchers/ComparableWatcher.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 
@@ -42,7 +40,8 @@ namespace StardewModdingAPI.Framework.StateTracking.FieldWatchers
         {
             this.GetValue = getValue;
             this.Comparer = comparer;
-            this.PreviousValue = getValue();
+            this.CurrentValue = getValue();
+            this.PreviousValue = this.CurrentValue;
         }
 
         /// <summary>Update the current value if needed.</summary>
diff --git a/src/SMAPI/Framework/StateTracking/PlayerTracker.cs b/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
index 367eafea..5433ac8e 100644
--- a/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
+++ b/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
@@ -1,7 +1,6 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using StardewModdingAPI.Enums;
 using StardewModdingAPI.Framework.StateTracking.Comparers;
@@ -23,7 +22,7 @@ namespace StardewModdingAPI.Framework.StateTracking
         private IDictionary<Item, int> CurrentInventory;
 
         /// <summary>The player's last valid location.</summary>
-        private GameLocation LastValidLocation;
+        private GameLocation? LastValidLocation;
 
         /// <summary>The underlying watchers.</summary>
         private readonly List<IWatcher> Watchers = new();
@@ -36,7 +35,7 @@ namespace StardewModdingAPI.Framework.StateTracking
         public Farmer Player { get; }
 
         /// <summary>The player's current location.</summary>
-        public IValueWatcher<GameLocation> LocationWatcher { get; }
+        public IValueWatcher<GameLocation?> LocationWatcher { get; }
 
         /// <summary>Tracks changes to the player's skill levels.</summary>
         public IDictionary<SkillType, IValueWatcher<int>> SkillWatchers { get; }
@@ -51,7 +50,8 @@ namespace StardewModdingAPI.Framework.StateTracking
         {
             // init player data
             this.Player = player;
-            this.PreviousInventory = this.GetInventory();
+            this.CurrentInventory = this.GetInventory();
+            this.PreviousInventory = new Dictionary<Item, int>(this.CurrentInventory);
 
             // init trackers
             this.LocationWatcher = WatcherFactory.ForReference(this.GetCurrentLocation);
@@ -95,7 +95,7 @@ namespace StardewModdingAPI.Framework.StateTracking
 
         /// <summary>Get the player's current location, ignoring temporary null values.</summary>
         /// <remarks>The game will set <see cref="Character.currentLocation"/> to null in some cases, e.g. when they're a secondary player in multiplayer and transition to a location that hasn't been synced yet. While that's happening, this returns the player's last valid location instead.</remarks>
-        public GameLocation GetCurrentLocation()
+        public GameLocation? GetCurrentLocation()
         {
             return this.Player.currentLocation ?? this.LastValidLocation;
         }
@@ -103,7 +103,7 @@ namespace StardewModdingAPI.Framework.StateTracking
         /// <summary>Get the inventory changes since the last update, if anything changed.</summary>
         /// <param name="changes">The inventory changes, or <c>null</c> if nothing changed.</param>
         /// <returns>Returns whether anything changed.</returns>
-        public bool TryGetInventoryChanges(out SnapshotItemListDiff changes)
+        public bool TryGetInventoryChanges([NotNullWhen(true)] out SnapshotItemListDiff? changes)
         {
             IDictionary<Item, int> current = this.GetInventory();
 
@@ -124,7 +124,7 @@ namespace StardewModdingAPI.Framework.StateTracking
         public void Dispose()
         {
             this.PreviousInventory.Clear();
-            this.CurrentInventory?.Clear();
+            this.CurrentInventory.Clear();
 
             foreach (IWatcher watcher in this.Watchers)
                 watcher.Dispose();
diff --git a/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs b/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
index bf81a35e..6a24ec30 100644
--- a/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
+++ b/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -47,17 +45,18 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
         public PlayerSnapshot(Farmer player)
         {
             this.Player = player;
+            this.Inventory = this.EmptyItemListDiff;
         }
 
         /// <summary>Update the tracked values.</summary>
         /// <param name="watcher">The player watcher to snapshot.</param>
         public void Update(PlayerTracker watcher)
         {
-            this.Location.Update(watcher.LocationWatcher);
-            foreach (var pair in this.Skills)
-                pair.Value.Update(watcher.SkillWatchers[pair.Key]);
+            this.Location.Update(watcher.LocationWatcher!);
+            foreach ((SkillType skill, var value) in this.Skills)
+                value.Update(watcher.SkillWatchers[skill]);
 
-            this.Inventory = watcher.TryGetInventoryChanges(out SnapshotItemListDiff itemChanges)
+            this.Inventory = watcher.TryGetInventoryChanges(out SnapshotItemListDiff? itemChanges)
                 ? itemChanges
                 : this.EmptyItemListDiff;
         }