Null type error message improvements

lib/Document.ts

@@ -335,7 +335,7 @@ Document.objectFromSchema = async function (object: any, model: Model<Document>,
 		if (existsInSchema) {
 			const {isValidType, matchedTypeDetails, typeDetailsArray} = utils.dynamoose.getValueTypeCheckResult(schema, value, genericKey, settings, {"standardKey": true, typeIndexOptionMap});
 			if (!isValidType) {
-				throw new Error.TypeMismatch(`Expected ${key} to be of type ${typeDetailsArray.map((detail) => detail.dynamicName ? detail.dynamicName() : detail.name.toLowerCase()).join(", ")}, instead found type ${typeof value}${typeDetailsArray.some((val) => val.name === "Constant") ? ` (${value})` : ""}.`);
+				throw new Error.TypeMismatch(`Expected ${key} to be of type ${typeDetailsArray.map((detail) => detail.dynamicName ? detail.dynamicName() : detail.name.toLowerCase()).join(", ")}, instead found type ${utils.type_name(value, typeDetailsArray)}.`);
 			} else if (matchedTypeDetails.isSet || matchedTypeDetails.name.toLowerCase() === "model") {
 				validParents.push({key, "infinite": true});
 			} else if (/*typeDetails.dynamodbType === "M" || */matchedTypeDetails.dynamodbType === "L") {

lib/utils/index.ts

@@ -9,6 +9,7 @@ import empty_function = require("./empty_function");
 import object = require("./object");
 import dynamoose = require("./dynamoose");
 import all_elements_match from "./all_elements_match";
+import type_name from "./type_name";
 
 export = {
 	combine_objects,
@@ -21,5 +22,6 @@ export = {
 	array_flatten,
 	empty_function,
 	object,
-	dynamoose
+	dynamoose,
+	type_name
 };

lib/utils/type_name.ts

@@ -0,0 +1,16 @@
+import {DynamoDBSetTypeResult, DynamoDBTypeResult} from "../Schema";
+
+// This function takes in a value and returns a user string for the type of that value. This function is mostly used to display type errors to users.
+export default (value: any, typeDetailsArray: (DynamoDBTypeResult | DynamoDBSetTypeResult)[]): string => {
+	let str = "";
+	if (value === null) {
+		str += "null";
+	} else {
+		str += typeof value;
+	}
+
+	// Add constant value to type name
+	str += typeDetailsArray.some((val) => val.name === "Constant") ? ` (${value})` : "";
+
+	return str;
+};

test/unit/Document.js

@@ -2750,6 +2750,11 @@ describe("Document", () => {
 					return {"id": Number, "data": [{"type": Set, "schema": [Item]}, String]};
 				},
 				"error": new Error.ValidationError("Expected data to be of type Item Set, string, instead found type boolean.")
+			},
+			{
+				"input": [{"id": 1, "data": null}, {"type": "toDynamo"}],
+				"schema": {"id": Number, "data": String},
+				"error": new Error.ValidationError("Expected data to be of type string, instead found type null.")
 			}
 		];