Fix accidental truncation of multi-line error messages

Fixes #1995.

lib/serialize-error.js

@@ -107,7 +107,16 @@ function trySerializeError(err, shouldBeautifyStack) {
 		} else {
 			// Skip the source line header inserted by `esm`:
 			// <https://github.com/standard-things/esm/wiki/improved-errors>
-			retval.summary = lines.find(line => !/:\d+$/.test(line));
+			const start = lines.findIndex(line => !/:\d+$/.test(line));
+			retval.summary = '';
+			for (let index = start; index < lines.length; index++) {
+				if (lines[index].startsWith('    at')) {
+					break;
+				}
+				const next = index + 1;
+				const end = next === lines.length || lines[next].startsWith('    at');
+				retval.summary += end ? lines[index] : lines[index] + '\n';
+			}
 		}
 	}
 

test/serialize-error.js

@@ -180,10 +180,10 @@ test('creates multiline summaries for syntax errors', t => {
 test('skips esm enhancement lines when finding the summary', t => {
 	const error = new Error();
 	Object.defineProperty(error, 'stack', {
-		value: 'file://file.js:1\nHello'
+		value: 'file://file.js:1\nFirst line\nSecond line'
 	});
 	const serializedError = serialize(error);
-	t.is(serializedError.summary, 'Hello');
+	t.is(serializedError.summary, 'First line\nSecond line');
 	t.end();
 });