Crash in LSHTTPStubURLProtocol - EXC_BAD_ACCESS - Specific way to stub redirects?

[JamieREvans]

I'm getting a crash on line 54 of LSHTTPStubURLProtocol:

[redirectRequest setAllHTTPHeaderFields:[NSHTTPCookie requestHeaderFieldsWithCookies:[cookieStorage cookiesForURL:newURL]]];

Here is the stack trace:

#0  0x000000010fd4a1d1 in CFURLCopyAbsoluteURL ()
#1  0x000000011211e3eb in HTTPCookieStorage::copyCookiesForURL(__CFURL const*, unsigned char) ()
#2  0x0000000112240c3f in -[NSHTTPCookieStorage cookiesForURL:] ()
#3  0x0000000119d6fa45 in -[LSHTTPStubURLProtocol startLoading] at /Users/Jamie/Development/Experiments/SampleCedarAsync/Pods/Nocilla/Nocilla/Hooks/NSURLRequest/LSHTTPStubURLProtocol.m:54
#4  0x0000000112206560 in ___ZN19URLConnectionLoader27_private_ScheduleOriginLoadEPK12NSURLRequestPK20_CFCachedURLResponse_block_invoke_2 ()
#5  0x0000000112119a5b in ___ZNK19URLConnectionLoader25withExistingProtocolAsyncEU13block_pointerFvP11URLProtocolE_block_invoke ()
#6  0x0000000112119a26 in RunloopBlockContext::_invoke_block(void const*, void*) ()
#7  0x000000010fd7a354 in CFArrayApplyFunction ()
#8  0x00000001121198e7 in RunloopBlockContext::perform() ()
#9  0x0000000112119726 in MultiplexerSource::perform() ()
#10 0x000000011211953c in MultiplexerSource::_perform(void*) ()
#11 0x000000010fda7431 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ ()
#12 0x000000010fd9d2fd in __CFRunLoopDoSources0 ()
#13 0x000000010fd9c934 in __CFRunLoopRun ()
#14 0x000000010fd9c366 in CFRunLoopRunSpecific ()
#15 0x000000011219f24d in +[NSURLConnection(Loader) _resourceLoadLoop:] ()
#16 0x000000010f6c109d in __NSThread__main__ ()
#17 0x0000000111dd5268 in _pthread_body ()
#18 0x0000000111dd51e5 in _pthread_start ()
#19 0x0000000111dd341d in thread_start ()

My testing code is as follows:

#import <Cedar/Cedar.h>
#import "CedarAsync.h"
#import "NSClient.h"
#import "Nocilla.h"

using namespace Cedar::Matchers;
using namespace Cedar::Doubles;

SPEC_BEGIN(NetworkSpec)

describe(@"Network", ^{

    __block NSClient *subject;
    __block NSUInteger returnedStatusCode;

    beforeEach(^{

        [[LSNocilla sharedInstance] start];

        subject = [NSClient clientWithScheme:@"http" andHost:@"google.ca"];

        stubRequest(kHTTPMethodGet, subject.baseURL.absoluteString).andReturn(303);

        [subject sendRequestWithEndpoint:nil
                          httpMethodType:NSHTTPMethodTypeGet
                             requestType:NSRequestTypeURL
                              dataObject:nil
                    requestMutationBlock:nil
                             andCallback:^(NSUInteger statusCode, id responseObject, NSError *error)
         {
             returnedStatusCode = statusCode; 
         }];
    });

    afterEach(^{

        [[LSNocilla sharedInstance] clearStubs];
        [[LSNocilla sharedInstance] stop];
    });

    it(@"should return a 303", ^{

        in_time(returnedStatusCode) should equal(303);
    });
});

SPEC_END

It seems that further documentation is needed for how to use Nocilla with redirects, as it's not clear that you must include the Location header in the stub itself.

[paudav]

Just so we're on the same page, it's important to note that HTTP requires that you include a Location header when responding with a 3XX code (https://tools.ietf.org/html/rfc2616#section-10.3).

Since this is all very standard stuff, I wouldn't really describe it as documentation needed for using Nocilla with redirects; I'd just say that it's generally what you need to do when responding with a redirect.

Now, the crash that you're seeing here is happening because Nocilla isn't doing appropriate checks for nil when it retrieves the Location header. In my opinion, this is just a bug that happens to be fatal if you don't stub a well-formed redirect. I've documented this along with a few other redirect quirks in issue #124.