Merge branch 'develop' into stable

10 files changed, 185 insertions, 71 deletions

diff --git a/src/SMAPI.Toolkit/Serialization/Converters/ManifestContentPackForConverter.cs b/src/SMAPI.Toolkit/Serialization/Converters/ManifestContentPackForConverter.cs
index 5cabe9d8..faaeedea 100644
--- a/src/SMAPI.Toolkit/Serialization/Converters/ManifestContentPackForConverter.cs
+++ b/src/SMAPI.Toolkit/Serialization/Converters/ManifestContentPackForConverter.cs
@@ -33,7 +33,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="objectType">The object type.</param>
         /// <param name="existingValue">The object being read.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
         {
             return serializer.Deserialize<ManifestContentPackFor>(reader);
         }
@@ -42,7 +42,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="writer">The JSON writer.</param>
         /// <param name="value">The value.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
         {
             throw new InvalidOperationException("This converter does not write JSON.");
         }
diff --git a/src/SMAPI.Toolkit/Serialization/Converters/ManifestDependencyArrayConverter.cs b/src/SMAPI.Toolkit/Serialization/Converters/ManifestDependencyArrayConverter.cs
index 7b88d6b7..c499a2c6 100644
--- a/src/SMAPI.Toolkit/Serialization/Converters/ManifestDependencyArrayConverter.cs
+++ b/src/SMAPI.Toolkit/Serialization/Converters/ManifestDependencyArrayConverter.cs
@@ -35,13 +35,13 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="objectType">The object type.</param>
         /// <param name="existingValue">The object being read.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        public override object ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
         {
             List<ManifestDependency> result = new List<ManifestDependency>();
             foreach (JObject obj in JArray.Load(reader).Children<JObject>())
             {
-                string uniqueID = obj.ValueIgnoreCase<string>(nameof(ManifestDependency.UniqueID));
-                string minVersion = obj.ValueIgnoreCase<string>(nameof(ManifestDependency.MinimumVersion));
+                string uniqueID = obj.ValueIgnoreCase<string>(nameof(ManifestDependency.UniqueID))!; // will be validated separately if null
+                string? minVersion = obj.ValueIgnoreCase<string>(nameof(ManifestDependency.MinimumVersion));
                 bool required = obj.ValueIgnoreCase<bool?>(nameof(ManifestDependency.IsRequired)) ?? true;
                 result.Add(new ManifestDependency(uniqueID, minVersion, required));
             }
@@ -52,7 +52,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="writer">The JSON writer.</param>
         /// <param name="value">The value.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
         {
             throw new InvalidOperationException("This converter does not write JSON.");
         }
diff --git a/src/SMAPI.Toolkit/Serialization/Converters/SemanticVersionConverter.cs b/src/SMAPI.Toolkit/Serialization/Converters/SemanticVersionConverter.cs
index cf69104d..c32c3185 100644
--- a/src/SMAPI.Toolkit/Serialization/Converters/SemanticVersionConverter.cs
+++ b/src/SMAPI.Toolkit/Serialization/Converters/SemanticVersionConverter.cs
@@ -39,15 +39,17 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="objectType">The object type.</param>
         /// <param name="existingValue">The object being read.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
         {
             string path = reader.Path;
             switch (reader.TokenType)
             {
                 case JsonToken.StartObject:
                     return this.ReadObject(JObject.Load(reader));
+
                 case JsonToken.String:
                     return this.ReadString(JToken.Load(reader).Value<string>(), path);
+
                 default:
                     throw new SParseException($"Can't parse {nameof(ISemanticVersion)} from {reader.TokenType} node (path: {reader.Path}).");
             }
@@ -57,7 +59,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="writer">The JSON writer.</param>
         /// <param name="value">The value.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
         {
             writer.WriteValue(value?.ToString());
         }
@@ -73,7 +75,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
             int major = obj.ValueIgnoreCase<int>(nameof(ISemanticVersion.MajorVersion));
             int minor = obj.ValueIgnoreCase<int>(nameof(ISemanticVersion.MinorVersion));
             int patch = obj.ValueIgnoreCase<int>(nameof(ISemanticVersion.PatchVersion));
-            string prereleaseTag = obj.ValueIgnoreCase<string>(nameof(ISemanticVersion.PrereleaseTag));
+            string? prereleaseTag = obj.ValueIgnoreCase<string>(nameof(ISemanticVersion.PrereleaseTag));
 
             return new SemanticVersion(major, minor, patch, prereleaseTag: prereleaseTag);
         }
@@ -81,11 +83,11 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <summary>Read a JSON string.</summary>
         /// <param name="str">The JSON string value.</param>
         /// <param name="path">The path to the current JSON node.</param>
-        private ISemanticVersion ReadString(string str, string path)
+        private ISemanticVersion? ReadString(string str, string path)
         {
             if (string.IsNullOrWhiteSpace(str))
                 return null;
-            if (!SemanticVersion.TryParse(str, allowNonStandard: this.AllowNonStandard, out ISemanticVersion version))
+            if (!SemanticVersion.TryParse(str, allowNonStandard: this.AllowNonStandard, out ISemanticVersion? version))
                 throw new SParseException($"Can't parse semantic version from invalid value '{str}', should be formatted like 1.2, 1.2.30, or 1.2.30-beta (path: {path}).");
             return version;
         }
diff --git a/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs b/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
index ccc5158b..1c59f5e7 100644
--- a/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
+++ b/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
@@ -25,21 +25,12 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
             return objectType == typeof(T) || Nullable.GetUnderlyingType(objectType) == typeof(T);
         }
 
-        /// <summary>Writes the JSON representation of the object.</summary>
-        /// <param name="writer">The JSON writer.</param>
-        /// <param name="value">The value.</param>
-        /// <param name="serializer">The calling serializer.</param>
-        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
-        {
-            throw new InvalidOperationException("This converter does not write JSON.");
-        }
-
         /// <summary>Reads the JSON representation of the object.</summary>
         /// <param name="reader">The JSON reader.</param>
         /// <param name="objectType">The object type.</param>
         /// <param name="existingValue">The object being read.</param>
         /// <param name="serializer">The calling serializer.</param>
-        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
         {
             string path = reader.Path;
             switch (reader.TokenType)
@@ -58,6 +49,15 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
             }
         }
 
+        /// <summary>Writes the JSON representation of the object.</summary>
+        /// <param name="writer">The JSON writer.</param>
+        /// <param name="value">The value.</param>
+        /// <param name="serializer">The calling serializer.</param>
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
+        {
+            throw new InvalidOperationException("This converter does not write JSON.");
+        }
+
 
         /*********
         ** Protected methods
diff --git a/src/SMAPI.Toolkit/Serialization/InternalExtensions.cs b/src/SMAPI.Toolkit/Serialization/InternalExtensions.cs
index 10f88dde..78297035 100644
--- a/src/SMAPI.Toolkit/Serialization/InternalExtensions.cs
+++ b/src/SMAPI.Toolkit/Serialization/InternalExtensions.cs
@@ -10,12 +10,12 @@ namespace StardewModdingAPI.Toolkit.Serialization
         /// <typeparam name="T">The value type.</typeparam>
         /// <param name="obj">The JSON object to search.</param>
         /// <param name="fieldName">The field name.</param>
-        public static T ValueIgnoreCase<T>(this JObject obj, string fieldName)
+        public static T? ValueIgnoreCase<T>(this JObject obj, string fieldName)
         {
-            JToken token = obj.GetValue(fieldName, StringComparison.OrdinalIgnoreCase);
+            JToken? token = obj.GetValue(fieldName, StringComparison.OrdinalIgnoreCase);
             return token != null
                 ? token.Value<T>()
-                : default(T);
+                : default;
         }
     }
 }
diff --git a/src/SMAPI.Toolkit/Serialization/JsonHelper.cs b/src/SMAPI.Toolkit/Serialization/JsonHelper.cs
index 00db9903..3c9308f2 100644
--- a/src/SMAPI.Toolkit/Serialization/JsonHelper.cs
+++ b/src/SMAPI.Toolkit/Serialization/JsonHelper.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
@@ -14,7 +15,7 @@ namespace StardewModdingAPI.Toolkit.Serialization
         ** Accessors
         *********/
         /// <summary>The JSON settings to use when serializing and deserializing files.</summary>
-        public JsonSerializerSettings JsonSettings { get; } = new JsonSerializerSettings
+        public JsonSerializerSettings JsonSettings { get; } = new()
         {
             Formatting = Formatting.Indented,
             ObjectCreationHandling = ObjectCreationHandling.Replace, // avoid issue where default ICollection<T> values are duplicated each time the config is loaded
@@ -36,7 +37,12 @@ namespace StardewModdingAPI.Toolkit.Serialization
         /// <returns>Returns false if the file doesn't exist, else true.</returns>
         /// <exception cref="ArgumentException">The given <paramref name="fullPath"/> is empty or invalid.</exception>
         /// <exception cref="JsonReaderException">The file contains invalid JSON.</exception>
-        public bool ReadJsonFileIfExists<TModel>(string fullPath, out TModel result)
+        public bool ReadJsonFileIfExists<TModel>(string fullPath,
+#if NET5_0_OR_GREATER
+            [NotNullWhen(true)]
+#endif
+            out TModel? result
+        )
         {
             // validate
             if (string.IsNullOrWhiteSpace(fullPath))
@@ -48,9 +54,9 @@ namespace StardewModdingAPI.Toolkit.Serialization
             {
                 json = File.ReadAllText(fullPath);
             }
-            catch (Exception ex) when (ex is DirectoryNotFoundException || ex is FileNotFoundException)
+            catch (Exception ex) when (ex is DirectoryNotFoundException or FileNotFoundException)
             {
-                result = default(TModel);
+                result = default;
                 return false;
             }
 
@@ -58,7 +64,7 @@ namespace StardewModdingAPI.Toolkit.Serialization
             try
             {
                 result = this.Deserialize<TModel>(json);
-                return true;
+                return result != null;
             }
             catch (Exception ex)
             {
@@ -88,7 +94,7 @@ namespace StardewModdingAPI.Toolkit.Serialization
                 throw new ArgumentException("The file path is empty or invalid.", nameof(fullPath));
 
             // create directory if needed
-            string dir = Path.GetDirectoryName(fullPath);
+            string dir = Path.GetDirectoryName(fullPath)!;
             if (dir == null)
                 throw new ArgumentException("The file path is invalid.", nameof(fullPath));
             if (!Directory.Exists(dir))
@@ -106,7 +112,8 @@ namespace StardewModdingAPI.Toolkit.Serialization
         {
             try
             {
-                return JsonConvert.DeserializeObject<TModel>(json, this.JsonSettings);
+                return JsonConvert.DeserializeObject<TModel>(json, this.JsonSettings)
+                    ?? throw new InvalidOperationException($"Couldn't deserialize model type '{typeof(TModel)}' from empty or null JSON.");
             }
             catch (JsonReaderException)
             {
@@ -115,7 +122,8 @@ namespace StardewModdingAPI.Toolkit.Serialization
                 {
                     try
                     {
-                        return JsonConvert.DeserializeObject<TModel>(json.Replace('“', '"').Replace('”', '"'), this.JsonSettings);
+                        return JsonConvert.DeserializeObject<TModel>(json.Replace('“', '"').Replace('”', '"'), this.JsonSettings)
+                            ?? throw new InvalidOperationException($"Couldn't deserialize model type '{typeof(TModel)}' from empty or null JSON.");
                     }
                     catch { /* rethrow original error */ }
                 }
diff --git a/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs b/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
index 46b654a5..da3ad608 100644
--- a/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
+++ b/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
@@ -1,5 +1,6 @@
+using System;
 using System.Collections.Generic;
-using System.Runtime.Serialization;
+using System.Diagnostics.CodeAnalysis;
 using Newtonsoft.Json;
 using StardewModdingAPI.Toolkit.Serialization.Converters;
 
@@ -12,48 +13,45 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
         ** Accessors
         *********/
         /// <summary>The mod name.</summary>
-        public string Name { get; set; }
+        public string Name { get; }
 
         /// <summary>A brief description of the mod.</summary>
-        public string Description { get; set; }
+        public string Description { get; }
 
         /// <summary>The mod author's name.</summary>
-        public string Author { get; set; }
+        public string Author { get; }
 
         /// <summary>The mod version.</summary>
-        public ISemanticVersion Version { get; set; }
+        public ISemanticVersion Version { get; }
 
         /// <summary>The minimum SMAPI version required by this mod, if any.</summary>
-        public ISemanticVersion MinimumApiVersion { get; set; }
+        public ISemanticVersion? MinimumApiVersion { get; }
 
         /// <summary>The name of the DLL in the directory that has the <c>Entry</c> method. Mutually exclusive with <see cref="ContentPackFor"/>.</summary>
-        public string EntryDll { get; set; }
+        public string? EntryDll { get; }
 
         /// <summary>The mod which will read this as a content pack. Mutually exclusive with <see cref="Manifest.EntryDll"/>.</summary>
         [JsonConverter(typeof(ManifestContentPackForConverter))]
-        public IManifestContentPackFor ContentPackFor { get; set; }
+        public IManifestContentPackFor? ContentPackFor { get; }
 
         /// <summary>The other mods that must be loaded before this mod.</summary>
         [JsonConverter(typeof(ManifestDependencyArrayConverter))]
-        public IManifestDependency[] Dependencies { get; set; }
+        public IManifestDependency[] Dependencies { get; }
 
         /// <summary>The namespaced mod IDs to query for updates (like <c>Nexus:541</c>).</summary>
-        public string[] UpdateKeys { get; set; }
+        public string[] UpdateKeys { get; private set; }
 
         /// <summary>The unique mod ID.</summary>
-        public string UniqueID { get; set; }
+        public string UniqueID { get; }
 
         /// <summary>Any manifest fields which didn't match a valid field.</summary>
         [JsonExtensionData]
-        public IDictionary<string, object> ExtraFields { get; set; }
+        public IDictionary<string, object> ExtraFields { get; } = new Dictionary<string, object>();
 
 
         /*********
         ** Public methods
         *********/
-        /// <summary>Construct an instance.</summary>
-        public Manifest() { }
-
         /// <summary>Construct an instance for a transitional content pack.</summary>
         /// <param name="uniqueID">The unique mod ID.</param>
         /// <param name="name">The mod name.</param>
@@ -61,24 +59,71 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
         /// <param name="description">A brief description of the mod.</param>
         /// <param name="version">The mod version.</param>
         /// <param name="contentPackFor">The modID which will read this as a content pack.</param>
-        public Manifest(string uniqueID, string name, string author, string description, ISemanticVersion version, string contentPackFor = null)
+        public Manifest(string uniqueID, string name, string author, string description, ISemanticVersion version, string? contentPackFor = null)
+            : this(
+                uniqueId: uniqueID,
+                name: name,
+                author: author,
+                description: description,
+                version: version,
+                minimumApiVersion: null,
+                entryDll: null,
+                contentPackFor: contentPackFor != null
+                    ? new ManifestContentPackFor(contentPackFor, null)
+                    : null,
+                dependencies: null,
+                updateKeys: null
+            )
+        { }
+
+        /// <summary>Construct an instance for a transitional content pack.</summary>
+        /// <param name="uniqueId">The unique mod ID.</param>
+        /// <param name="name">The mod name.</param>
+        /// <param name="author">The mod author's name.</param>
+        /// <param name="description">A brief description of the mod.</param>
+        /// <param name="version">The mod version.</param>
+        /// <param name="minimumApiVersion">The minimum SMAPI version required by this mod, if any.</param>
+        /// <param name="entryDll">The name of the DLL in the directory that has the <c>Entry</c> method. Mutually exclusive with <see cref="ContentPackFor"/>.</param>
+        /// <param name="contentPackFor">The modID which will read this as a content pack.</param>
+        /// <param name="dependencies">The other mods that must be loaded before this mod.</param>
+        /// <param name="updateKeys">The namespaced mod IDs to query for updates (like <c>Nexus:541</c>).</param>
+        [JsonConstructor]
+        public Manifest(string uniqueId, string name, string author, string description, ISemanticVersion version, ISemanticVersion? minimumApiVersion, string? entryDll, IManifestContentPackFor? contentPackFor, IManifestDependency[]? dependencies, string[]? updateKeys)
         {
-            this.Name = name;
-            this.Author = author;
-            this.Description = description;
+            this.UniqueID = this.NormalizeWhitespace(uniqueId);
+            this.Name = this.NormalizeWhitespace(name);
+            this.Author = this.NormalizeWhitespace(author);
+            this.Description = this.NormalizeWhitespace(description);
             this.Version = version;
-            this.UniqueID = uniqueID;
-            this.UpdateKeys = new string[0];
-            this.ContentPackFor = new ManifestContentPackFor { UniqueID = contentPackFor };
+            this.MinimumApiVersion = minimumApiVersion;
+            this.EntryDll = this.NormalizeWhitespace(entryDll);
+            this.ContentPackFor = contentPackFor;
+            this.Dependencies = dependencies ?? Array.Empty<IManifestDependency>();
+            this.UpdateKeys = updateKeys ?? Array.Empty<string>();
+        }
+
+        /// <summary>Override the update keys loaded from the mod info.</summary>
+        /// <param name="updateKeys">The new update keys to set.</param>
+        internal void OverrideUpdateKeys(params string[] updateKeys)
+        {
+            this.UpdateKeys = updateKeys;
         }
 
-        /// <summary>Normalize the model after it's deserialized.</summary>
-        /// <param name="context">The deserialization context.</param>
-        [OnDeserialized]
-        public void OnDeserialized(StreamingContext context)
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Normalize whitespace in a raw string.</summary>
+        /// <param name="input">The input to strip.</param>
+#if NET5_0_OR_GREATER
+        [return: NotNullIfNotNull("input")]
+#endif
+        private string? NormalizeWhitespace(string? input)
         {
-            this.Dependencies ??= new IManifestDependency[0];
-            this.UpdateKeys ??= new string[0];
+            return input
+                ?.Trim()
+                .Replace("\r", "")
+                .Replace("\n", "");
         }
     }
 }
diff --git a/src/SMAPI.Toolkit/Serialization/Models/ManifestContentPackFor.cs b/src/SMAPI.Toolkit/Serialization/Models/ManifestContentPackFor.cs
index 1eb80889..f7dc8aa8 100644
--- a/src/SMAPI.Toolkit/Serialization/Models/ManifestContentPackFor.cs
+++ b/src/SMAPI.Toolkit/Serialization/Models/ManifestContentPackFor.cs
@@ -1,3 +1,5 @@
+using System.Diagnostics.CodeAnalysis;
+
 namespace StardewModdingAPI.Toolkit.Serialization.Models
 {
     /// <summary>Indicates which mod can read the content pack represented by the containing manifest.</summary>
@@ -7,9 +9,36 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
         ** Accessors
         *********/
         /// <summary>The unique ID of the mod which can read this content pack.</summary>
-        public string UniqueID { get; set; }
+        public string UniqueID { get; }
 
         /// <summary>The minimum required version (if any).</summary>
-        public ISemanticVersion MinimumVersion { get; set; }
+        public ISemanticVersion? MinimumVersion { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="uniqueId">The unique ID of the mod which can read this content pack.</param>
+        /// <param name="minimumVersion">The minimum required version (if any).</param>
+        public ManifestContentPackFor(string uniqueId, ISemanticVersion? minimumVersion)
+        {
+            this.UniqueID = this.NormalizeWhitespace(uniqueId);
+            this.MinimumVersion = minimumVersion;
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Normalize whitespace in a raw string.</summary>
+        /// <param name="input">The input to strip.</param>
+#if NET5_0_OR_GREATER
+        [return: NotNullIfNotNull("input")]
+#endif
+        private string? NormalizeWhitespace(string? input)
+        {
+            return input?.Trim();
+        }
     }
 }
diff --git a/src/SMAPI.Toolkit/Serialization/Models/ManifestDependency.cs b/src/SMAPI.Toolkit/Serialization/Models/ManifestDependency.cs
index 00f168f4..fa254ea7 100644
--- a/src/SMAPI.Toolkit/Serialization/Models/ManifestDependency.cs
+++ b/src/SMAPI.Toolkit/Serialization/Models/ManifestDependency.cs
@@ -1,3 +1,6 @@
+using System.Diagnostics.CodeAnalysis;
+using Newtonsoft.Json;
+
 namespace StardewModdingAPI.Toolkit.Serialization.Models
 {
     /// <summary>A mod dependency listed in a mod manifest.</summary>
@@ -7,13 +10,13 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
         ** Accessors
         *********/
         /// <summary>The unique mod ID to require.</summary>
-        public string UniqueID { get; set; }
+        public string UniqueID { get; }
 
         /// <summary>The minimum required version (if any).</summary>
-        public ISemanticVersion MinimumVersion { get; set; }
+        public ISemanticVersion? MinimumVersion { get; }
 
         /// <summary>Whether the dependency must be installed to use the mod.</summary>
-        public bool IsRequired { get; set; }
+        public bool IsRequired { get; }
 
 
         /*********
@@ -23,13 +26,40 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
         /// <param name="uniqueID">The unique mod ID to require.</param>
         /// <param name="minimumVersion">The minimum required version (if any).</param>
         /// <param name="required">Whether the dependency must be installed to use the mod.</param>
-        public ManifestDependency(string uniqueID, string minimumVersion, bool required = true)
+        public ManifestDependency(string uniqueID, string? minimumVersion, bool required = true)
+            : this(
+                uniqueID: uniqueID,
+                minimumVersion: !string.IsNullOrWhiteSpace(minimumVersion)
+                    ? new SemanticVersion(minimumVersion)
+                    : null,
+                required: required
+            )
+        { }
+
+        /// <summary>Construct an instance.</summary>
+        /// <param name="uniqueID">The unique mod ID to require.</param>
+        /// <param name="minimumVersion">The minimum required version (if any).</param>
+        /// <param name="required">Whether the dependency must be installed to use the mod.</param>
+        [JsonConstructor]
+        public ManifestDependency(string uniqueID, ISemanticVersion? minimumVersion, bool required = true)
         {
-            this.UniqueID = uniqueID;
-            this.MinimumVersion = !string.IsNullOrWhiteSpace(minimumVersion)
-                ? new SemanticVersion(minimumVersion)
-                : null;
+            this.UniqueID = this.NormalizeWhitespace(uniqueID);
+            this.MinimumVersion = minimumVersion;
             this.IsRequired = required;
         }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Normalize whitespace in a raw string.</summary>
+        /// <param name="input">The input to strip.</param>
+#if NET5_0_OR_GREATER
+        [return: NotNullIfNotNull("input")]
+#endif
+        private string? NormalizeWhitespace(string? input)
+        {
+            return input?.Trim();
+        }
     }
 }
diff --git a/src/SMAPI.Toolkit/Serialization/SParseException.cs b/src/SMAPI.Toolkit/Serialization/SParseException.cs
index 5f58b5b8..c2b3f68e 100644
--- a/src/SMAPI.Toolkit/Serialization/SParseException.cs
+++ b/src/SMAPI.Toolkit/Serialization/SParseException.cs
@@ -11,7 +11,7 @@ namespace StardewModdingAPI.Toolkit.Serialization
         /// <summary>Construct an instance.</summary>
         /// <param name="message">The error message.</param>
         /// <param name="ex">The underlying exception, if any.</param>
-        public SParseException(string message, Exception ex = null)
+        public SParseException(string message, Exception? ex = null)
             : base(message, ex) { }
     }
 }