Fix to handle invalid API directions

[hunterlindsay]

Background

On Thursday the 20th (late morning) and Friday the 21st of August NZST a Mapbox API change caused our iOS app to crash on start up when retrieving directions. This was caused by forcibly unwrapping a nil optional in RoadClasses.swift (line 102).

The change to the API was subsequently rolled back, but it bricked our production app for over a day.

Changes

• Use an optional binding to throw a DirectionsError which can be handled by the caller, instead of causing a fatal error.

Crash Report

Retrieved from Crashlytics:

Crashed: com.apple.root.user-initiated-qos
EXC_BREAKPOINT 0x0000000105b104a8

Crashed: com.apple.root.user-initiated-qos
0  MapboxDirections               0x105b104a8 $s16MapboxDirections11RoadClassesV4fromACs7Decoder_p_tKcfCTf4nd_n + 276
1  MapboxDirections               0x105b100bc $s16MapboxDirections11RoadClassesVSeAASe4fromxs7Decoder_p_tKcfCTW + 20
2  libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
3  libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
4  libswiftFoundation.dylib       0x1bc6c7d4c _JSONKeyedDecodingContainer.decode<A>(_:forKey:) + 560
5  libswiftFoundation.dylib       0x1bc7139d0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 36
6  libswiftFoundation.dylib       0x1bc6c9ff0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 20
7  libswiftCore.dylib             0x19336374c KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) + 208
8  libswiftFoundation.dylib       0x1bc6ca23c protocol witness for KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 32
9  libswiftCore.dylib             0x193369f3c _KeyedDecodingContainerBox.decodeIfPresent<A>(_:forKey:) + 40
10 libswiftCore.dylib             0x193363d50 KeyedDecodingContainer.decodeIfPresent<A>(_:forKey:) + 40
11 MapboxDirections               0x105aff738 $s16MapboxDirections12IntersectionV4fromACs7Decoder_p_tKcfC + 1924
12 MapboxDirections               0x105affb90 $s16MapboxDirections12IntersectionVSeAASe4fromxs7Decoder_p_tKcfCTW + 12
13 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
14 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
15 libswiftFoundation.dylib       0x1bc6ca8cc _JSONUnkeyedDecodingContainer.decode<A>(_:) + 756
16 libswiftFoundation.dylib       0x1bc6cce94 protocol witness for UnkeyedDecodingContainer.decode<A>(_:) in conformance _JSONUnkeyedDecodingContainer + 12
17 libswiftCore.dylib             0x1933717b0 Array<A>.init(from:) + 384
18 libswiftCore.dylib             0x193371f10 protocol witness for Decodable.init(from:) in conformance <A> [A] + 28
19 libswiftCore.dylib             0x19337197c protocol witness for Decodable.init(from:) in conformance <A> [A] + 20
20 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
21 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
22 libswiftFoundation.dylib       0x1bc6c7d4c _JSONKeyedDecodingContainer.decode<A>(_:forKey:) + 560
23 libswiftFoundation.dylib       0x1bc7139d0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 36
24 libswiftFoundation.dylib       0x1bc6c9ff0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 20
25 libswiftCore.dylib             0x19336374c KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) + 208
26 libswiftFoundation.dylib       0x1bc6ca23c protocol witness for KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 32
27 libswiftCore.dylib             0x193369f3c _KeyedDecodingContainerBox.decodeIfPresent<A>(_:forKey:) + 40
28 libswiftCore.dylib             0x193363d50 KeyedDecodingContainer.decodeIfPresent<A>(_:forKey:) + 40
29 MapboxDirections               0x105b26a44 $s16MapboxDirections9RouteStepC4fromACs7Decoder_p_tKcfc + 2904
30 MapboxDirections               0x105b25edc $s16MapboxDirections9RouteStepC4fromACs7Decoder_p_tKcfC + 56
31 MapboxDirections               0x105b2772c $s16MapboxDirections9RouteStepCSeAASe4fromxs7Decoder_p_tKcfCTW + 24
32 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
33 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
34 libswiftFoundation.dylib       0x1bc6ca8cc _JSONUnkeyedDecodingContainer.decode<A>(_:) + 756
35 libswiftFoundation.dylib       0x1bc6cce94 protocol witness for UnkeyedDecodingContainer.decode<A>(_:) in conformance _JSONUnkeyedDecodingContainer + 12
36 libswiftCore.dylib             0x1933717b0 Array<A>.init(from:) + 384
37 libswiftCore.dylib             0x193371f10 protocol witness for Decodable.init(from:) in conformance <A> [A] + 28
38 libswiftCore.dylib             0x19337197c protocol witness for Decodable.init(from:) in conformance <A> [A] + 20
39 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
40 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
41 libswiftFoundation.dylib       0x1bc6c7d4c _JSONKeyedDecodingContainer.decode<A>(_:forKey:) + 560
42 libswiftFoundation.dylib       0x1bc7139d0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 36
43 libswiftFoundation.dylib       0x1bc6c9ff0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 20
44 libswiftCore.dylib             0x193369bd0 _KeyedDecodingContainerBox.decode<A>(_:forKey:) + 40
45 libswiftCore.dylib             0x19331edbc KeyedDecodingContainer.decode<A>(_:forKey:) + 40
46 MapboxDirections               0x105b12b6c $s16MapboxDirections8RouteLegC4fromACs7Decoder_p_tKcfc + 1412
47 MapboxDirections               0x105b125d8 $s16MapboxDirections8RouteLegC4fromACs7Decoder_p_tKcfC + 56
48 MapboxDirections               0x105b14f2c $s16MapboxDirections8RouteLegCSeAASe4fromxs7Decoder_p_tKcfCTW + 24
49 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
50 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
51 libswiftFoundation.dylib       0x1bc6ca8cc _JSONUnkeyedDecodingContainer.decode<A>(_:) + 756
52 libswiftFoundation.dylib       0x1bc6cce94 protocol witness for UnkeyedDecodingContainer.decode<A>(_:) in conformance _JSONUnkeyedDecodingContainer + 12
53 libswiftCore.dylib             0x1933717b0 Array<A>.init(from:) + 384
54 libswiftCore.dylib             0x193371f10 protocol witness for Decodable.init(from:) in conformance <A> [A] + 28
55 libswiftCore.dylib             0x19337197c protocol witness for Decodable.init(from:) in conformance <A> [A] + 20
56 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
57 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
58 libswiftFoundation.dylib       0x1bc6c7d4c _JSONKeyedDecodingContainer.decode<A>(_:forKey:) + 560
59 libswiftFoundation.dylib       0x1bc7139d0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 36
60 libswiftFoundation.dylib       0x1bc6c9ff0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 20
61 libswiftCore.dylib             0x193369bd0 _KeyedDecodingContainerBox.decode<A>(_:forKey:) + 40
62 libswiftCore.dylib             0x19331edbc KeyedDecodingContainer.decode<A>(_:forKey:) + 40
63 MapboxDirections               0x105af8ef0 $s16MapboxDirections0B6ResultC4fromACs7Decoder_p_tKcfc + 908
64 MapboxDirections               0x105b10800 $s16MapboxDirections5RouteC4fromACs7Decoder_p_tKcfC + 56
65 MapboxDirections               0x105afa730 $s16MapboxDirections0B6ResultCSeAASe4fromxs7Decoder_p_tKcfCTW + 24
66 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
67 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
68 libswiftFoundation.dylib       0x1bc6ca8cc _JSONUnkeyedDecodingContainer.decode<A>(_:) + 756
69 libswiftFoundation.dylib       0x1bc6cce94 protocol witness for UnkeyedDecodingContainer.decode<A>(_:) in conformance _JSONUnkeyedDecodingContainer + 12
70 libswiftCore.dylib             0x1933717b0 Array<A>.init(from:) + 384
71 libswiftCore.dylib             0x193371f10 protocol witness for Decodable.init(from:) in conformance <A> [A] + 28
72 libswiftCore.dylib             0x19337197c protocol witness for Decodable.init(from:) in conformance <A> [A] + 20
73 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
74 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
75 libswiftFoundation.dylib       0x1bc6c7d4c _JSONKeyedDecodingContainer.decode<A>(_:forKey:) + 560
76 libswiftFoundation.dylib       0x1bc7139d0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 36
77 libswiftFoundation.dylib       0x1bc6c9ff0 protocol witness for KeyedDecodingContainerProtocol.decode<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 20
78 libswiftCore.dylib             0x19336374c KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) + 208
79 libswiftFoundation.dylib       0x1bc6ca23c protocol witness for KeyedDecodingContainerProtocol.decodeIfPresent<A>(_:forKey:) in conformance _JSONKeyedDecodingContainer<A> + 32
80 libswiftCore.dylib             0x193369f3c _KeyedDecodingContainerBox.decodeIfPresent<A>(_:forKey:) + 40
81 libswiftCore.dylib             0x193363d50 KeyedDecodingContainer.decodeIfPresent<A>(_:forKey:) + 40
82 MapboxDirections               0x105b1cabc $s16MapboxDirections13RouteResponseV4fromACs7Decoder_p_tKcfC + 2932
83 MapboxDirections               0x105b1d9d4 $s16MapboxDirections13RouteResponseVSeAASe4fromxs7Decoder_p_tKcfCTW + 12
84 libswiftCore.dylib             0x19343d914 dispatch thunk of Decodable.init(from:) + 16
85 libswiftFoundation.dylib       0x1bc6d2f8c __JSONDecoder.unbox_(_:as:) + 3276
86 libswiftFoundation.dylib       0x1bc6bdab0 JSONDecoder.decode<A>(_:from:) + 888
87 libswiftFoundation.dylib       0x1bc786680 dispatch thunk of JSONDecoder.decode<A>(_:from:) + 20
88 MapboxDirections               0x105ae2f9c $s16MapboxDirections0B0C9calculate_17completionHandlerSo20NSURLSessionDataTaskCAA12RouteOptionsC_yAA0bJ0C7options_AA0B11CredentialsV11credentialst_s6ResultOyAA0I8ResponseVAA0B5ErrorOGtctFy10Foundation0G0VSg_So13NSURLResponseCSgs0P0_pSgtcfU_yycfU2_ + 1400
89 MapboxDirections               0x105aea1d4 $s16MapboxDirections0B0C15calculateRoutes8matching17completionHandlerSo20NSURLSessionDataTaskCAA12MatchOptionsC_yAA0bL0C7options_AA0B11CredentialsV11credentialst_s6ResultOyAA13RouteResponseVAA0B5ErrorOGtctFy10Foundation0I0VSg_So13NSURLResponseCSgs0S0_pSgtcfU_yycfU2_TATm + 44
90 MapboxDirections               0x105ae2a14 $sIeg_IeyB_TR + 28
91 libdispatch.dylib              0x1859aa9a8 _dispatch_call_block_and_release + 24
92 libdispatch.dylib              0x1859ab524 _dispatch_client_callout + 16
93 libdispatch.dylib              0x18599165c _dispatch_root_queue_drain + 640
94 libdispatch.dylib              0x185991cd0 _dispatch_worker_thread2 + 112
95 libsystem_pthread.dylib        0x1859fcb38 _pthread_wqthread + 212
96 libsystem_pthread.dylib        0x1859ff740 start_wqthread + 8

[1ec5]

Thanks! I agree that we need additional safety on the client-side here.

[1ec5]

Cherry-picked to the master and main branches in 4d7ea73.

[1ec5]

Added to the changelog in 0c97fed.