fix build warnings

src/SMAPI.Toolkit/Framework/LowLevelEnvironmentUtility.cs

@@ -22,7 +22,7 @@ namespace StardewModdingAPI.Toolkit.Framework
         /// <param name="buffer">The buffer to fill with the resulting string.</param>
         [DllImport("libc")]
         [SuppressMessage("ReSharper", "IdentifierTypo", Justification = "This is the actual external command name.")]
-        static extern int uname(IntPtr buffer);
+        private static extern int uname(IntPtr buffer);
 
 
         /*********

src/SMAPI.Toolkit/ModToolkit.cs

@@ -65,7 +65,7 @@ namespace StardewModdingAPI.Toolkit
         /// <param name="metadataPath">The file path for the SMAPI metadata file.</param>
         public ModDatabase GetModDatabase(string metadataPath)
         {
-            MetadataModel metadata = JsonConvert.DeserializeObject<MetadataModel>(File.ReadAllText(metadataPath));
+            MetadataModel metadata = JsonConvert.DeserializeObject<MetadataModel>(File.ReadAllText(metadataPath)) ?? new MetadataModel();
             ModDataRecord[] records = metadata.ModData.Select(pair => new ModDataRecord(pair.Key, pair.Value)).ToArray();
             return new ModDatabase(records, this.GetUpdateUrl);
         }

src/SMAPI.Toolkit/Serialization/Converters/SemanticVersionConverter.cs

@@ -48,7 +48,12 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
                     return this.ReadObject(JObject.Load(reader));
 
                 case JsonToken.String:
-                    return this.ReadString(JToken.Load(reader).Value<string>(), path);
+                    {
+                        string? value = JToken.Load(reader).Value<string>();
+                        return value is not null
+                            ? this.ReadString(value, path)
+                            : null;
+                    }
 
                 default:
                     throw new SParseException($"Can't parse {nameof(ISemanticVersion)} from {reader.TokenType} node (path: {reader.Path}).");

src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs

@@ -42,7 +42,12 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
                     return this.ReadObject(JObject.Load(reader), path);
 
                 case JsonToken.String:
-                    return this.ReadString(JToken.Load(reader).Value<string>(), path);
+                    {
+                        string? value = JToken.Load(reader).Value<string>();
+                        return value is not null
+                            ? this.ReadString(value, path)
+                            : null;
+                    }
 
                 default:
                     throw new SParseException($"Can't parse {typeof(T).Name} from {reader.TokenType} node (path: {reader.Path}).");

src/SMAPI/Framework/ModHelpers/ModHelper.cs

@@ -88,6 +88,7 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <param name="modDirectory">The full path to the mod's folder.</param>
         /// <param name="currentInputState">Manages the game's input state for the current player instance. That may not be the main player in split-screen mode.</param>
         /// <param name="events">Manages access to events raised by SMAPI.</param>
+        /// <param name="contentHelper">An API for loading content assets.</param>
         /// <param name="gameContentHelper">An API for loading content assets from the game's <c>Content</c> folder or via <see cref="IModEvents.Content"/>.</param>
         /// <param name="modContentHelper">An API for loading content assets from your mod's files.</param>
         /// <param name="contentPackHelper">An API for managing content packs.</param>

src/SMAPI/Framework/Models/SConfig.cs

@@ -100,7 +100,7 @@ namespace StardewModdingAPI.Framework.Models
         /// <param name="logNetworkTraffic">Whether SMAPI should log network traffic.</param>
         /// <param name="consoleColors">The colors to use for text written to the SMAPI console.</param>
         /// <param name="suppressUpdateChecks">The mod IDs SMAPI should ignore when performing update checks or validating update keys.</param>
-        public SConfig(bool developerMode, bool? checkForUpdates, bool? paranoidWarnings, bool? useBetaChannel, string gitHubProjectName, string webApiBaseUrl, string[]? verboseLogging, bool? rewriteMods, bool? usePintail, bool? useRawImageLoading, bool? useCaseInsensitivePaths, bool? logNetworkTraffic, ColorSchemeConfig consoleColors, string[]? suppressUpdateChecks)
+        public SConfig(bool developerMode, bool? checkForUpdates, bool? paranoidWarnings, bool? useBetaChannel, string gitHubProjectName, string webApiBaseUrl, string[]? verboseLogging, bool? rewriteMods, bool? useRawImageLoading, bool? useCaseInsensitivePaths, bool? logNetworkTraffic, ColorSchemeConfig consoleColors, string[]? suppressUpdateChecks)
         {
             this.DeveloperMode = developerMode;
             this.CheckForUpdates = checkForUpdates ?? (bool)SConfig.DefaultValues[nameof(this.CheckForUpdates)];

src/SMAPI/Framework/SCore.cs

@@ -191,7 +191,7 @@ namespace StardewModdingAPI.Framework
             string logPath = this.GetLogPath();
 
             // init basics
-            this.Settings = JsonConvert.DeserializeObject<SConfig>(File.ReadAllText(Constants.ApiConfigPath));
+            this.Settings = JsonConvert.DeserializeObject<SConfig>(File.ReadAllText(Constants.ApiConfigPath)) ?? throw new InvalidOperationException("The 'smapi-internal/config.json' file is missing or invalid. You can reinstall SMAPI to fix this.");
             if (File.Exists(Constants.ApiUserConfigPath))
                 JsonConvert.PopulateObject(File.ReadAllText(Constants.ApiUserConfigPath), this.Settings);
             if (developerMode.HasValue)

src/SMAPI/Framework/Serialization/KeybindConverter.cs

@@ -49,7 +49,10 @@ namespace StardewModdingAPI.Framework.Serialization
 
                 case JsonToken.String:
                     {
-                        string str = JToken.Load(reader).Value<string>();
+                        string? str = JToken.Load(reader).Value<string>();
+
+                        if (str is null)
+                            return new Keybind(Array.Empty<SButton>());
 
                         if (objectType == typeof(Keybind))
                         {

src/SMAPI/Utilities/SDate.cs

@@ -278,11 +278,11 @@ namespace StardewModdingAPI.Utilities
 
         /// <summary>Get whether a date represents 0 spring Y1, which is the date during the in-game intro.</summary>
         /// <param name="day">The day of month.</param>
-        /// <param name="season">The season name.</param>
+        /// <param name="season">The normalized season name.</param>
         /// <param name="year">The year.</param>
         private bool IsDayZero(int day, string season, int year)
         {
-            return day == 0 && season?.Trim().ToLower() == "spring" && year == 1;
+            return day == 0 && season == "spring" && year == 1;
         }
 
         /// <summary>Get the day of week for a given date.</summary>