1 files changed, 96 insertions, 0 deletions
diff --git a/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs b/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
index 8a449f0a..4f84a60d 100644
--- a/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
+++ b/src/SMAPI.Toolkit/Serialization/Models/Manifest.cs
@@ -1,9 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Linq;
 using System.Text;
 using Newtonsoft.Json;
 using StardewModdingAPI.Toolkit.Serialization.Converters;
+using StardewModdingAPI.Toolkit.Utilities;
 
 namespace StardewModdingAPI.Toolkit.Serialization.Models
 {
@@ -103,6 +106,99 @@ namespace StardewModdingAPI.Toolkit.Serialization.Models
             this.UpdateKeys = updateKeys ?? Array.Empty<string>();
         }
 
+        /// <summary>Try to validate a manifest's fields. Fails if any invalid field is found.</summary>
+        /// <param name="error">The error message to display to the user.</param>
+        /// <returns>Returns whether the manifest was validated successfully.</returns>
+        public bool TryValidate(out string error)
+        {
+            // validate DLL / content pack fields
+            bool hasDll = !string.IsNullOrWhiteSpace(this.EntryDll);
+            bool isContentPack = this.ContentPackFor != null;
+
+            // validate field presence
+            if (!hasDll && !isContentPack)
+            {
+                error = $"manifest has no {nameof(IManifest.EntryDll)} or {nameof(IManifest.ContentPackFor)} field; must specify one.";
+                return false;
+            }
+            if (hasDll && isContentPack)
+            {
+                error = $"manifest sets both {nameof(IManifest.EntryDll)} and {nameof(IManifest.ContentPackFor)}, which are mutually exclusive.";
+                return false;
+            }
+
+            // validate DLL filename format
+            if (hasDll && this.EntryDll!.Intersect(Path.GetInvalidFileNameChars()).Any())
+            {
+                error = $"manifest has invalid filename '{this.EntryDll}' for the EntryDLL field.";
+                return false;
+            }
+
+            // validate content pack
+            else if (isContentPack)
+            {
+                // invalid content pack ID
+                if (string.IsNullOrWhiteSpace(this.ContentPackFor!.UniqueID))
+                {
+                    error = $"manifest declares {nameof(IManifest.ContentPackFor)} without its required {nameof(IManifestContentPackFor.UniqueID)} field.";
+                    return false;
+                }
+            }
+
+            // validate required fields
+            {
+                List<string> missingFields = new List<string>(3);
+
+                if (string.IsNullOrWhiteSpace(this.Name))
+                    missingFields.Add(nameof(IManifest.Name));
+                if (this.Version == null || this.Version.ToString() == "0.0.0")
+                    missingFields.Add(nameof(IManifest.Version));
+                if (string.IsNullOrWhiteSpace(this.UniqueID))
+                    missingFields.Add(nameof(IManifest.UniqueID));
+
+                if (missingFields.Any())
+                {
+                    error = $"manifest is missing required fields ({string.Join(", ", missingFields)}).";
+                    return false;
+                }
+            }
+
+            // validate ID format
+            if (!PathUtilities.IsSlug(this.UniqueID))
+            {
+                error = "manifest specifies an invalid ID (IDs must only contain letters, numbers, underscores, periods, or hyphens).";
+                return false;
+            }
+
+            // validate dependencies
+            foreach (IManifestDependency? dependency in this.Dependencies)
+            {
+                // null dependency
+                if (dependency == null)
+                {
+                    error = $"manifest has a null entry under {nameof(IManifest.Dependencies)}.";
+                    return false;
+                }
+
+                // missing ID
+                if (string.IsNullOrWhiteSpace(dependency.UniqueID))
+                {
+                    error = $"manifest has a {nameof(IManifest.Dependencies)} entry with no {nameof(IManifestDependency.UniqueID)} field.";
+                    return false;
+                }
+
+                // invalid ID
+                if (!PathUtilities.IsSlug(dependency.UniqueID))
+                {
+                    error = $"manifest has a {nameof(IManifest.Dependencies)} entry with an invalid {nameof(IManifestDependency.UniqueID)} field (IDs must only contain letters, numbers, underscores, periods, or hyphens).";
+                    return false;
+                }
+            }
+
+            error = "";
+            return true;
+        }
+
         /// <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)