App: add error handling

lib/app.js

@@ -17,14 +17,15 @@ const CORS = ({ origin='*', methods='HEAD,PUT,DELETE,POST,GET,OPTIONS', max_age=
 class App {
 	static CORS = CORS;
 
-	constructor(router, preprocessors=[], postprocessors=[]) {
+	constructor(router, preprocessors=[], postprocessors=[], error_handler=null) {
 		if(!router) {
 			throw new Error('Please instanciate app with a root router');
 		}
 
 		this.router = router;
 		this.preprocessors = preprocessors;
 		this.postprocessors = postprocessors;
+		this.error_handler = null;
 	}
 
 	// Registers pre-processors
@@ -119,6 +120,10 @@ class App {
 		});
 	}
 
+	error(callback) {
+		this.error_handler = callback;
+	}
+
 	run(event) {
 		const { request } = event;
 		const { callback, params } = this.router.route(request);
@@ -134,7 +139,10 @@ class App {
 			return this.postprocess(response, request, params, event);
 		}).catch(e => {
 			// Handle 500
-			console.error(e);
+			if(this.error_handler) {
+				return this.error_handler(e, request, params, event);
+			}
+
 			return new Response(null, { status: 500 });
 		});
 	}

test/app/app.js

@@ -228,4 +228,34 @@ describe('App', () => {
 			done();
 		}).catch(e => done(e));
 	});
+
+	describe('Error handling', () => {
+		it('Should register an error handler and call it', done => {
+			const router = new Router();
+
+			router.get('/plep/:plop', () => {
+				throw new Error('Simulated error');
+			});
+
+			const app = new App(router);
+
+			app.error((err, request, params, event) => {
+				return new Response('test', {
+					status: 505
+				});
+			});
+
+			app.run({
+				request: {
+					url: 'https://google.com/plep/5',
+					method: 'GET'
+				}
+			}).then(result => {
+				expect(result).to.be.instanceof(Response);
+				expect(result.status).to.be.eql(505);
+				expect(result.body).to.be.eql('test');
+				done();
+			}).catch(e => done(e));
+		});
+	});
 });