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felangelfelangel
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feat(dart_frog): add cascade (#98)
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‎packages/dart_frog/lib/dart_frog.dart

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@@ -3,6 +3,7 @@ library dart_frog;
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export 'src/_internal.dart'
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show
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Cascade,
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Pipeline,
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Request,
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RequestContext,

‎packages/dart_frog/lib/src/_internal.dart

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@@ -6,6 +6,7 @@ import 'package:http_methods/http_methods.dart' show isHttpMethod;
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import 'package:shelf/shelf.dart' as shelf;
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import 'package:shelf/shelf_io.dart' as shelf_io;
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part 'cascade.dart';
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part 'pipeline.dart';
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part 'request.dart';
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part 'context.dart';

‎packages/dart_frog/lib/src/cascade.dart

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part of '_internal.dart';
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/// {@template cascade}
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/// A class that supports calling multiple handlers
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/// in sequence and returns the first acceptable response.
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///
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/// By default, a response is considered acceptable if it has a status other
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/// than 404 or 405; other statuses indicate that the handler understood the
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/// request.
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///
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/// If all handlers return unacceptable responses, the final response will be
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/// returned.
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///
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/// ```dart
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/// final handler = Cascade()
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/// .add(staticAssetHandler)
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/// .add(router)
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/// .handler;
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/// ```
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/// {@endtemplate}
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class Cascade {
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/// {@macro cascade}
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Cascade({
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Iterable<int>? statusCodes,
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bool Function(Response)? shouldCascade,
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}) : this._(
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shelf.Cascade(
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statusCodes: statusCodes,
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shouldCascade: shouldCascade != null
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? (response) => shouldCascade(Response._(response))
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: null,
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),
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);
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Cascade._(this._cascade);
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final shelf.Cascade _cascade;
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/// Returns a new [Cascade] instance with the [handler] added to the end.
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///
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/// The provided [handler] will only be called if all previous
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/// handlers in the cascade return unacceptable responses.
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Cascade add(Handler handler) {
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return Cascade._(_cascade.add(toShelfHandler(handler)));
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}
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/// Exposes this cascade as a single handler.
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///
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/// This handler will call each inner handler in the cascade until one returns
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/// an acceptable response, and return that. If no inner handlers return an
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/// acceptable response, this will return the final response.
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Handler get handler => fromShelfHandler(_cascade.handler);
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}

‎packages/dart_frog/test/src/cascade_test.dart

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import 'dart:io';
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import 'package:dart_frog/dart_frog.dart';
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import 'package:mocktail/mocktail.dart';
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import 'package:test/test.dart';
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final _request = Request('GET', _localhostUri);
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final _localhostUri = Uri.parse('http://localhost/');
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Future<Response> _makeSimpleRequest(Handler handler) {
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return Future.sync(() => handler(_SimpleRequestContext()));
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}
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class _MockRequestContext extends Mock implements RequestContext {}
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class _SimpleRequestContext extends Fake implements RequestContext {
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@override
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Request get request => _request;
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}
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void main() {
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group('Cascade', () {
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group('a cascade with several handlers', () {
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late Handler handler;
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setUp(() {
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Response handler1(RequestContext context) {
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if (context.request.headers['one'] == 'false') {
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return Response(statusCode: HttpStatus.notFound, body: 'handler 1');
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} else {
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return Response(body: 'handler 1');
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}
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}
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Response handler2(RequestContext context) {
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if (context.request.headers['two'] == 'false') {
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return Response(statusCode: HttpStatus.notFound, body: 'handler 2');
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} else {
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return Response(body: 'handler 2');
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}
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}
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Response handler3(RequestContext context) {
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if (context.request.headers['three'] == 'false') {
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return Response(statusCode: HttpStatus.notFound, body: 'handler 3');
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} else {
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return Response(body: 'handler 3');
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}
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}
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handler = Cascade().add(handler1).add(handler2).add(handler3).handler;
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});
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test('the first response should be returned if it matches', () async {
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final response = await _makeSimpleRequest(handler);
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expect(response.statusCode, equals(200));
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expect(response.body(), completion(equals('handler 1')));
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});
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test(
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'the second response should be returned if it matches and the first '
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"doesn't", () async {
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final context = _MockRequestContext();
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final request = Request(
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'GET',
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_localhostUri,
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headers: {'one': 'false'},
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);
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when(() => context.request).thenReturn(request);
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final response = await handler(context);
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expect(response.statusCode, equals(200));
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expect(response.body(), completion(equals('handler 2')));
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});
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test(
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'the third response should be returned if it matches and the first '
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"two don't", () async {
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final context = _MockRequestContext();
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final request = Request(
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'GET',
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_localhostUri,
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headers: {'one': 'false', 'two': 'false'},
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);
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when(() => context.request).thenReturn(request);
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final response = await handler(context);
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expect(response.statusCode, equals(200));
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expect(response.body(), completion(equals('handler 3')));
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});
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test('the third response should be returned if no response matches',
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() async {
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final context = _MockRequestContext();
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final request = Request(
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'GET',
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_localhostUri,
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headers: {'one': 'false', 'two': 'false', 'three': 'false'},
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);
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when(() => context.request).thenReturn(request);
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final response = await handler(context);
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expect(response.statusCode, equals(404));
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expect(response.body(), completion(equals('handler 3')));
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});
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});
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test('a 404 response triggers a cascade by default', () async {
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final handler = Cascade()
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.add(
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(_) => Response(statusCode: HttpStatus.notFound, body: 'handler 1'),
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)
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.add((_) => Response(body: 'handler 2'))
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.handler;
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final response = await _makeSimpleRequest(handler);
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expect(response.statusCode, equals(200));
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expect(response.body(), completion(equals('handler 2')));
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});
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test('a 405 response triggers a cascade by default', () async {
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final handler = Cascade()
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.add((_) => Response(statusCode: 405))
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.add((_) => Response(body: 'handler 2'))
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.handler;
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final response = await _makeSimpleRequest(handler);
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expect(response.statusCode, equals(200));
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expect(response.body(), completion(equals('handler 2')));
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});
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test('[statusCodes] controls which statuses cause cascading', () async {
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final handler = Cascade(statusCodes: [302, 403])
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.add((_) => Response(statusCode: HttpStatus.found, body: '/'))
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.add(
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(_) =>
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Response(statusCode: HttpStatus.forbidden, body: 'handler 2'),
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)
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.add(
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(_) => Response(statusCode: HttpStatus.notFound, body: 'handler 3'),
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)
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.add((_) => Response(body: 'handler 4'))
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.handler;
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final response = await _makeSimpleRequest(handler);
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expect(response.statusCode, equals(404));
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expect(response.body(), completion(equals('handler 3')));
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});
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test('[shouldCascade] controls which responses cause cascading', () async {
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bool shouldCascade(Response response) => response.statusCode.isOdd;
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final handler = Cascade(shouldCascade: shouldCascade)
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.add(
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(_) => Response(statusCode: HttpStatus.movedPermanently, body: '/'),
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)
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.add(
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(_) =>
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Response(statusCode: HttpStatus.forbidden, body: 'handler 2'),
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)
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.add(
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(_) => Response(statusCode: HttpStatus.notFound, body: 'handler 3'),
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)
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.add((_) => Response(body: 'handler 4'))
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.handler;
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final response = await _makeSimpleRequest(handler);
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expect(response.statusCode, equals(404));
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expect(response.body(), completion(equals('handler 3')));
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});
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group('errors', () {
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test('getting the handler for an empty cascade fails', () {
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expect(() => Cascade().handler, throwsStateError);
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});
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test(
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'passing [statusCodes] and [shouldCascade] '
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'at the same time fails', () {
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expect(
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() => Cascade(statusCodes: [404, 405], shouldCascade: (_) => false),
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throwsArgumentError,
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);
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});
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});
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});
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}

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