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[SR-9749] The encodedOffset of String.Index has been changed to either UTF-8 or UTF-16. #52180

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norio-nomura opened this issue Jan 24, 2019 · 5 comments

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@norio-nomura
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norio-nomura commented Jan 24, 2019

Previous ID SR-9749
Radar rdar://problem/47605131
Original Reporter @norio-nomura
Type Bug
Status Resolved
Resolution Done
Environment

swift-DEVELOPMENT-SNAPSHOT-2019-01-23-a
swift-5.0-DEVELOPMENT-SNAPSHOT-2019-01-23-a

Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Bug
Assignee @milseman
Priority Medium

md5: 66ece592c380ddd277127ea29c649351

Issue Description:

The problem is:

  1. Before merging [String] Use a UTF-8 representation for native strings #20315, The encodedOffset of String.Index was specified as UTF-16 offset, and it actually worked as expected.

    /// The offset into a string's UTF-16 encoding for this index.
    @inlinable // FIXME(sil-serialize-all)
    public var encodedOffset : Int {

    https://github.com/apple/swift/pull/20315/files#diff-8ec9c169d4bc3c678838b4067481979eL130

    /// Creates a new index at the specified UTF-16 offset.
    ///
    /// - Parameter offset: An offset in UTF-16 code units.
    @inlinable // FIXME(sil-serialize-all)
    public init(encodedOffset offset: Int) {

    https://github.com/apple/swift/pull/20315/files#diff-8ec9c169d4bc3c678838b4067481979eL106

  2. A lot of codes were written that expect that behavior (including swift-corelibs-foundation)
    e.g. codes using encodedOffset in Swift on GitHub can be found: https://github.com/search?l=Swift&q=encodedOffset&type=Code

  3. However, the change is not written in changelog etc., and it is understood only from the description of UTF-16 deleted from each documentation comment. In fact, swift-corelibs-foundation did not recognize that change was necessary, which caused SR-9454.

I think that some countermeasures are necessary:

  • [MUST] Behavior changes should be documented (eg within changelog).

  • [MAY] Some code change
    Mark init(encodedOffset:) and encodedOffset as deprecated
    or
    Introduce new property exposing encode information(UTF-8 or UTF-16) to String

/cc: @milseman

@milseman
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Mannequin

milseman mannequin commented Jan 25, 2019

#22108

Will need release-noting as well.

@norio-nomura
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norio-nomura commented Jan 25, 2019

I am very happy that it seems to be adopting the best solution (I did not write on the issue) that I imagined! 😃

@norio-nomura
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norio-nomura commented Feb 12, 2019

Another example to fix an issue caused by wrong usage of encodedOffset.
apple/swift-corelibs-foundation#1894

@milseman
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Mannequin

milseman mannequin commented Apr 10, 2019

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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