[SR-6163] JSONDecoder cannot decode RFC 7159 JSON

[swift-ci]

Previous ID	SR-6163
Radar	rdar://problem/38549586
Original Reporter	mikkelam (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	23
Component/s	Foundation
Labels	Bug, Codable
Assignee	@itaiferber
Priority	Medium

md5: 7ea104c1b9f4df36ef6d428fc2c7cfd0

is duplicated by:

• SR-7213 Allow JSONEncoder to Encode Top-Level Fragments

relates to:

• SR-12275 JSONEncoder on Linux can't encode number JSON fragments

Issue Description:

For example

22

Is valid RFC 7159 JSON. This can be parsed using the JSONSerializer like so

let json = "22".data(using: .utf8)!

if let value = (try? JSONSerialization.jsonObject(with: json, options: .allowFragments)) as? Int {
    print(value) // 22
}

But there is no way to use the allowFragments option for JSONDecoder.

[itaiferber]

@swift-ci Create

[itaiferber]

As is discussed in https://forums.swift.org/t/top-level-t-self-encoded-as-number-json-fragment/11001, if we choose to, we can resolve this either on the JSONEncoder/JSONDecoder side, or on the JSONSerialization side (for encoding).

[swift-ci]

Comment by Vasily Anisimov (JIRA)

Hello! Any progress on this issue?

[itaiferber]

Yes, work has been ongoing internally, but I can't speak to the specifics here.

[benrimmington]

This appears to be resolved with the latest macOS and iOS.

JSONEncoder and JSONDecoder now support top-level "primitive" types (strings, numbers, booleans) by default.

But I can't see any relevant changes in the implementation or unit tests.

[swift-ci]

Comment by Andrey Yakushev (JIRA)

Looks like @benrimmington is right. Rechecked right now: tests are successful with Xcode 11 on iOS 13.1 and fail on iOS 10.3.1.

[swift-ci]

Comment by Chris Ballinger (JIRA)

As @benrimmington said, it looks like the open source release of Swift's Darwin JSONEncoder/JSONDecoder has not been updated to reflect this change, and doesn't match the stdlib that is being shipped with iOS 13:

• https://github.com/apple/swift/blob/6d8e5f19ecba7f3aef7701263b28e0afb46e868f/stdlib/public/Darwin/Foundation/JSONEncoder.swift#L273

• https://github.com/apple/swift/blob/6d8e5f19ecba7f3aef7701263b28e0afb46e868f/stdlib/public/Darwin/Foundation/JSONEncoder.swift#L1208

I guess Apple is shipping a private fork and forgot to upstream the fix?

[swift-ci]

Comment by Chris Ballinger (JIRA)

I made a small PR that updates the open source stdlib to match the behavior of the one shipping with iOS 13: swiftlang/swift#28818

[benrimmington]

Darwin:

• apple/swift#30615 (master)

• apple/swift#30616 (swift-5.2-branch)

Other platforms:

• apple/swift-corelibs-foundation#2713

[swift-ci]

Comment by Diogo Tridapalli (JIRA)

It's fixed on Xcode 11.4.

[benrimmington]

SR-12275 has been resolved.