Handle esm's error "improvements"

esm changes error stacks in a way that AVA is not expecting. This adds a
few workarounds, though admittedly all the packages we're using and
workarounds we're applying are making a bit of a mess.

See https://github.com/standard-things/esm/wiki/improved-errors for
esm's behavior.

lib/beautify-stack.js

@@ -68,5 +68,8 @@ module.exports = stack => {
 
 	return stackUtils.clean(stack)
 		// Remove the trailing newline inserted by the `stack-utils` module
-		.trim();
+		.trim()
+		// Remove remaining file:// prefixes, inserted by `esm`, that are not
+		// cleaned up by `stack-utils`
+		.split('\n').map(line => line.replace(/\(file:\/\/([^/].+:\d+:\d+)\)$/, '($1)')).join('\n');
 };

lib/serialize-error.js

@@ -101,7 +101,9 @@ function trySerializeError(err, shouldBeautifyStack) {
 			}
 			retval.summary = retval.summary.trim();
 		} else {
-			retval.summary = lines[0];
+			// 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));
 		}
 	}
 

test/serialize-error.js

@@ -176,3 +176,29 @@ test('creates multiline summaries for syntax errors', t => {
 	t.is(serializedError.summary, 'Hello\nThere\nSyntaxError here');
 	t.end();
 });
+
+test('skips esm enhancement lines when finding the summary', t => {
+	const error = new Error();
+	Object.defineProperty(error, 'stack', {
+		value: 'file://file.js:1\nHello'
+	});
+	const serializedError = serialize(error);
+	t.is(serializedError.summary, 'Hello');
+	t.end();
+});
+
+test('works around esm\'s insertion of file:// urls', t => {
+	const fixture = sourceMapFixtures.mapFile('throws');
+	try {
+		fixture.require().run();
+		t.fail('Fixture should have thrown');
+	} catch (error) {
+		const expected = serialize(error);
+		Object.defineProperty(error, 'stack', {
+			value: error.stack.split('\n').map(line => line.replace('(/', '(file:///')).join('\n')
+		});
+		const serializedError = serialize(error);
+		t.is(serializedError.source.file, expected.source.file);
+		t.end();
+	}
+});