More robust undefined value checking for format()

lib/errors/BlorkError.js

@@ -8,8 +8,6 @@ const ValueError = require("./ValueError");
  * - The type you're checking against (not the value you're checking) is invalid or doesn't exist.
  */
 class BlorkError extends ValueError {}
-BlorkError.name = "BlorkError";
-BlorkError.message = "Incorrect Blork configuration";
 
 // Exports.
 module.exports = BlorkError;

lib/errors/ValueError.js

@@ -14,16 +14,20 @@ class ValueError extends TypeError {
 	 * @param {mixed} value A value to debug shown at the end of the message, e.g. "Must be string (received 123)"
 	 * @param {string} prefix=undefined An optional prefix for the message e.g. the function name or the name of the value, e.g. "name: Must be string (received 123)"
 	 */
-	constructor(message, value = format.UNDEF, prefix = format.UNDEF) {
-		// Save message as normal.
-		super(format(message, value, prefix));
+	constructor(message = "Invalid value", value = undefined, prefix = "") {
+		// Save message through TypeError.
+		// We format immediately (rather than in toString) because Jest (and presumably others) call .message directly.
+		super(arguments.length > 1 ? format(message, value, prefix) : message);
 
-		// Save value separately.
-		if (value !== format.UNDEF) this.value = value;
+		// Save parts separately.
+		this.prefix = prefix;
+		this.reason = message;
+		if (arguments.length > 1) this.value = value;
+
+		// Save name as constructor name (e.g. ValueError).
+		this.name = this.constructor.name;
 	}
 }
-ValueError.name = "ValueError";
-ValueError.message = "Invalid value";
 
 // Exports.
 module.exports = ValueError;

lib/functions/format.js

@@ -1,8 +1,5 @@
 const debug = require("./debug");
 
-// Constants.
-const UNDEF = Symbol("UNDEF");
-
 /**
  * Format an error message.
  * Optionally with a prefix and a variable to debug.
@@ -12,15 +9,14 @@ const UNDEF = Symbol("UNDEF");
  * @param {string} prefix=undefined An optional prefix for the message e.g. the function name or the name of the value, e.g. "name: Must be string (received 123)"
  * @returns {string} The error message.
  */
-function format(message, value = UNDEF, prefix = UNDEF) {
+function format(message, value, prefix) {
 	// e.g. MyPrefix: Must be string (received 123)
 	return (
 		(typeof prefix === "string" && prefix.length > 0 ? `${prefix}: ` : "") +
 		message +
-		(value !== UNDEF ? ` (received ${debug(value)})` : "")
+		(arguments.length > 1 ? ` (received ${debug(value)})` : "")
 	);
 }
 
 // Exports.
 module.exports = format;
-module.exports.UNDEF = UNDEF;

test/errors/BlorkError.test.js

@@ -2,13 +2,27 @@ const BlorkError = require("../../lib/errors/BlorkError");
 
 // Tests.
 describe("BlorkError()", () => {
+	test("Return correct error with default message", () => {
+		expect(new BlorkError()).toHaveProperty("message");
+		expect(new BlorkError()).toHaveProperty("reason");
+		expect(new BlorkError()).not.toHaveProperty("value");
+	});
 	test("Return correct error with message only", () => {
 		expect(new BlorkError("Message")).toHaveProperty("message", "Message");
+		expect(new BlorkError("Message")).toHaveProperty("prefix", "");
+		expect(new BlorkError("Message")).toHaveProperty("reason", "Message");
+		expect(new BlorkError("Message")).not.toHaveProperty("value");
 	});
 	test("Return correct error with message and value", () => {
 		expect(new BlorkError("Message", 123)).toHaveProperty("message", "Message (received 123)");
+		expect(new BlorkError("Message", 123)).toHaveProperty("prefix", "");
+		expect(new BlorkError("Message", 123)).toHaveProperty("reason", "Message");
+		expect(new BlorkError("Message", 123)).toHaveProperty("value", 123);
 	});
 	test("Return correct error with message, value, and prefix", () => {
 		expect(new BlorkError("Message", 123, "Prefix")).toHaveProperty("message", "Prefix: Message (received 123)");
+		expect(new BlorkError("Message", 123, "Prefix")).toHaveProperty("prefix", "Prefix");
+		expect(new BlorkError("Message", 123, "Prefix")).toHaveProperty("reason", "Message");
+		expect(new BlorkError("Message", 123, "Prefix")).toHaveProperty("value", 123);
 	});
 });

test/errors/ValueError.test.js

@@ -0,0 +1,33 @@
+const ValueError = require("../../lib/errors/ValueError");
+
+// Tests.
+describe("ValueError()", () => {
+	test("Return correct error with default message", () => {
+		expect(new ValueError()).toHaveProperty("name", "ValueError");
+		expect(new ValueError()).toHaveProperty("message", "Invalid value");
+		expect(new ValueError()).toHaveProperty("prefix", "");
+		expect(new ValueError()).toHaveProperty("reason", "Invalid value");
+		expect(new ValueError()).not.toHaveProperty("value");
+	});
+	test("Return correct error with message only", () => {
+		expect(new ValueError("Message")).toHaveProperty("name", "ValueError");
+		expect(new ValueError("Message")).toHaveProperty("message", "Message");
+		expect(new ValueError("Message")).toHaveProperty("prefix", "");
+		expect(new ValueError("Message")).toHaveProperty("reason", "Message");
+		expect(new ValueError("Message")).not.toHaveProperty("value");
+	});
+	test("Return correct error with message and value", () => {
+		expect(new ValueError("Message", 123)).toHaveProperty("name", "ValueError");
+		expect(new ValueError("Message", 123)).toHaveProperty("message", "Message (received 123)");
+		expect(new ValueError("Message", 123)).toHaveProperty("prefix", "");
+		expect(new ValueError("Message", 123)).toHaveProperty("reason", "Message");
+		expect(new ValueError("Message", 123)).toHaveProperty("value", 123);
+	});
+	test("Return correct error with message, value, and prefix", () => {
+		expect(new ValueError("Message", 123, "Prefix")).toHaveProperty("name", "ValueError");
+		expect(new ValueError("Message", 123, "Prefix")).toHaveProperty("message", "Prefix: Message (received 123)");
+		expect(new ValueError("Message", 123, "Prefix")).toHaveProperty("prefix", "Prefix");
+		expect(new ValueError("Message", 123, "Prefix")).toHaveProperty("reason", "Message");
+		expect(new ValueError("Message", 123, "Prefix")).toHaveProperty("value", 123);
+	});
+});