[SR-13173] Foundation.JSONEncoder + Swift 5.2.4 + .allowFragments difference between macOS and Linux

[ktoso]

Previous ID	SR-13173
Radar	rdar://problem/65213214
Original Reporter	@ktoso
Type	Bug
Status	Resolved
Resolution	Done

Environment

Ubuntu, Swift 5.2.4-RELEASE

Additional Detail from JIRA

Votes	1
Component/s	Foundation
Labels	Bug, Codable
Assignee	None
Priority	Medium

md5: 4e72ea41a8582e0940c613e2d3fc8e5f

Issue Description:

I'm aware and very happy that this was fixed on master and will be fixed in Swift 5.3: #2713 ( https://bugs.swift.org/browse/SR-12275 https://bugs.swift.org/browse/SR-6163 ).

Things are not in sync between corelibs foundation and foundation on 5.2.4 though, which causes us a bunch of painful workaround and headaches - is there a chance that the patch will also apply to any 5.2.x if/when there's going to be one?

macOS, swift 5.2.4, good:

Welcome to Apple Swift version 5.2.4 (swift-5.2.4-RELEASE).
 1> import Foundation
 3> JSONDecoder().decode(Int.self, from: "23".data(using: .utf8)!)
$R1: Int = 23

ubuntu, swift 5.2.4, bad:

Welcome to Swift version 5.2.4 (swift-5.2.4-RELEASE).
1> import Foundation
3> let s = JSONDecoder().decode(Int.self, from: "42".data(using: .utf8)!)
s: Int = 0 // oh oh...

–

Things are correct on Swift 5.3, however we're not really ready to require users to bump to that version, so we're stuck with building manually looking ahead at the bytes if it maybe it a top level value and trying to handle it "manually" today...

[ktoso]

@swift-ci create

[ktoso]

PRed a backport: #2840

[ktoso]

This was fixed in 5.2.5