Support object syntax for validateArguments as well

src/api/validate-arguments.js

@@ -2,6 +2,7 @@
 
 const isArguments = require("is-arguments");
 const flatten = require("flatten");
+const asExpression = require("as-expression");
 
 const ValidationError = require("@validatem/error");
 const annotateErrors = require("@validatem/annotate-errors");
@@ -17,42 +18,68 @@ module.exports = createValidationMethod((args, argumentDefinitions) => {
 		throw new Error(`First argument is not an 'arguments' object; maybe you forgot to put it before the validation rules?`);
 	} else if (argumentDefinitions == null) {
 		throw new Error(`Validation rules (second argument) are missing; maybe you forgot to specify them?`);
-	} else if (args.length > argumentDefinitions.length) {
-		return {
-			errors: [ new ValidationError(`Got ${args.length} arguments, but only expected ${argumentDefinitions.length}`) ],
-			// Cast the below to an array, for consistency with *success* output, in case we ever want to expose the new values to the user in an error case too.
-			newValue: Array.from(args)
-		};
 	} else {
-		let results = argumentDefinitions.map((definition, i) => {
-			let argument = args[i];
-			let [ argumentName, ...argumentRules ] = definition;
+		let usesArrayAPI = (Array.isArray(argumentDefinitions));
 
-			if (typeof argumentName !== "string") {
-				throw new Error("First item in the argument rules list must be the argument name");
-			} else {
-				let validatorResult = applyValidators(argument, argumentRules);
+		let definitionCount = (usesArrayAPI)
+			? argumentDefinitions.length
+			: Object.keys(argumentDefinitions).length;
 
+		if (args.length > definitionCount) {
+			return {
+				errors: [ new ValidationError(`Got ${args.length} arguments, but only expected ${definitionCount}`) ],
+				// Cast the below to an array, for consistency with *success* output, in case we ever want to expose the new values to the user in an error case too.
+				newValue: Array.from(args)
+			};
+		} else {
+			let normalizedDefinitions = asExpression(() => {
+				if (usesArrayAPI) {
+					return argumentDefinitions.map((definition) => {
+						let [ name, ...rules ] = definition;
+
+						if (typeof name !== "string") {
+							throw new Error("First item in the argument rules list must be the argument name");
+						} else {
+							return {
+								name: name,
+								rules: rules
+							};
+						}
+					});
+				} else {
+					return Object.entries(argumentDefinitions).map(([ key, value ]) => {
+						return {
+							name: key,
+							rules: value
+						};
+					});
+				}
+			});
+
+			let results = normalizedDefinitions.map(({ name, rules }, i) => {
+				let argument = args[i];
+				let validatorResult = applyValidators(argument, rules);
+	
 				return {
 					errors: annotateErrors({
-						pathSegments: [ argumentName ],
+						pathSegments: [ name ],
 						errors: validatorResult.errors
 					}),
 					newValue: (validatorResult.newValue !== undefined)
 						? validatorResult.newValue
 						: argument
 				};
-			}
-		});
-
-		let combinedErrors = results.map((result) => result.errors);
-		let flattenedErrors = flatten(combinedErrors); // TODO: Switch to `Array#flat` once Node 10.x goes EOL (April 2021)
-
-		let newValues = results.map((result) => result.newValue);
-
-		return {
-			errors: flattenedErrors,
-			newValue: newValues
-		};
+			});
+	
+			let combinedErrors = results.map((result) => result.errors);
+			let flattenedErrors = flatten(combinedErrors); // TODO: Switch to `Array#flat` once Node 10.x goes EOL (April 2021)
+	
+			let newValues = results.map((result) => result.newValue);
+	
+			return {
+				errors: flattenedErrors,
+				newValue: newValues
+			};
+		}
 	}
 });