[SR-6729] URLQueryItem - Fails in Set Comparison

[swift-ci]

Previous ID	SR-6729
Radar	None
Original Reporter	sndmn (JIRA User)
Type	Bug

Environment

ubuntu 14.04

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Standard Library | |Labels | Bug, Linux | |Assignee | None | |Priority | Medium | md5: f2ff69b31de4428de85b37325a8afa2b

Issue Description:

On linux, comparison of URLQueryItems when within a Set fails intermittently. The issues seems to be Set related instead of URLQueryItem related, since comparing them directly always works as expected, but when placed into a Set the comparison fails about 40% of the time on linux. MacOS works as expected.

Below is a code Snippet, illustrating the problem.

```

let u1 = URLQueryItem(name: "intField", value: "1")

let u2 = URLQueryItem(name: "intField", value: "1")

let queryItems1 = [ u1 ]

let queryItems2 = [ u2 ]

assert(u1 == u2, "Individually: Works as expected")

assert(queryItems1, queryItems2, "Within an Array: Works as expected")

assert(Set(queryItems1) == Set(queryItems2), "Within a Set: Fails intermittently")

```

[belkadan]

cc @moiseev

[ee21ea02-9d7a-4385-8c3c-ad21e8e490a8]

Sounds AnyHashable-related. @lorentey has been working with hashed collections recently.

[lorentey]

This looks like a problem with NSURLQueryItem in open-source Foundation: it overrides isEqual but not hash, so it inherits NSObject's hash value implementation that is based on object identity. This violates the requirement that object equality implies hashValue equality, leading to all sorts of issues with Set/Dictionary.

The snippet below should print true, true, but on Linux, it currently prints true, false.

import Foundation
let a = URLQueryItem(name: "intField", value: "1")
let b = URLQueryItem(name: "intField", value: "1")
print(a == b, a.hashValue == b.hashValue)

NSURLComponents seems to have the same issue.

cc @phausler

[phausler]

yup, that should definitely be defined (and is currently not), the objc version uses the name hash with the value hash (which seems like what we should be doing in swift).

Looks like a good starter bug.