Created ModelNotFound ErrorCatchingSpecialization implementation

Author: calebkleveter

Sources/APIErrorMiddleware/APIErrorMiddleware.swift

@@ -13,9 +13,6 @@ public final class APIErrorMiddleware: Middleware, Service, ServiceType {
     /// to `ErrorResult` objects.
     let specializations: [ErrorCatchingSpecialization]
 
-    // We define an empty init because the one
-    // synthesized bby Swift is marked `internal`.
-    
     /// Create an instance if `APIErrorMiddleware`.
     public init(specializations: [ErrorCatchingSpecialization] = []) {
         self.specializations = specializations

Sources/APIErrorMiddleware/Specialization/Specialization.swift

@@ -37,3 +37,19 @@ public protocol ErrorCatchingSpecialization {
     ///   passed in.
     func convert(error: Error, on request: Request) -> ErrorResult?
 }
+
+// MARK: - ErrorCatchingSpecialization implementations
+
+/// Catches Fluent's `modelNotFound` error and returns a 404 status code.
+public struct ModelNotFound: ErrorCatchingSpecialization {
+    public func convert(error: Error, on request: Request) -> ErrorResult? {
+        if let error = error as? Debuggable, error.identifier == "modelNotFound" {
+            
+            // We have the infamous `modelNotFound` error from Fluent that returns
+            // a 500 status code instead of a 404.
+            // Set the message to the error's `reason` and the status to 404 (Not Found)
+            return ErrorResult(message: error.reason, status: .notFound)
+        }
+        return nil
+    }
+}