Tighten Error determination (#101)

index.js

@@ -196,15 +196,16 @@ export function deserializeError(value, options = {}) {
 export function isErrorLike(value) {
 	return Boolean(value)
 	&& typeof value === 'object'
-	&& 'name' in value
-	&& 'message' in value
-	&& 'stack' in value;
+	&& typeof value.name === 'string'
+	&& typeof value.message === 'string'
+	&& typeof value.stack === 'string';
 }
 
+// Used as a weak check for immediately-passed objects, whereas `isErrorLike` is used for nested values to avoid bad detection
 function isMinimumViableSerializedError(value) {
 	return Boolean(value)
 	&& typeof value === 'object'
-	&& 'message' in value
+	&& typeof value.message === 'string'
 	&& !Array.isArray(value);
 }
 

test.js

@@ -2,7 +2,12 @@ import {Buffer} from 'node:buffer';
 import Stream from 'node:stream';
 import test from 'ava';
 import errorConstructors from './error-constructors.js';
-import {serializeError, deserializeError, isErrorLike} from './index.js';
+import {
+	serializeError,
+	deserializeError,
+	isErrorLike,
+	NonError,
+} from './index.js';
 
 function deserializeNonError(t, value) {
 	const deserialized = deserializeError(value);
@@ -351,6 +356,44 @@ test('should deserialize properties up to `Options.maxDepth` levels deep', t =>
 	t.deepEqual(levelThree, error);
 });
 
+test('should ignore invalid error-like objects', t => {
+	const errorLike = {
+		name: 'Error',
+		message: 'Some error message',
+	};
+
+	const nonErrorLike = {
+		name: 'Error',
+		message: (new class Message {}('Bottle')),
+	};
+
+	t.true(deserializeError(errorLike) instanceof Error);
+	t.true(deserializeError(nonErrorLike) instanceof NonError);
+});
+
+test('should ignore nested invalid error-like objects', t => {
+	const errorLike = {
+		message: 'Base',
+		nested: {
+			name: 'Error',
+			message: 'Some error message',
+			stack: 'at <anonymous>:1:13',
+		},
+	};
+
+	const nonErrorLike = {
+		message: 'Base',
+		nested: {
+			name: 'Error',
+			message: (new class Message {}('Bottle')),
+			stack: 'at <anonymous>:1:13',
+		},
+	};
+
+	t.true(deserializeError(errorLike).nested instanceof Error);
+	t.false(deserializeError(nonErrorLike).nested instanceof Error);
+});
+
 test('should serialize Date as ISO string', t => {
 	const date = {date: new Date(0)};
 	const serialized = serializeError(date);