Added implementation of NSString init(contentsOfFile:usedEncoding:)

[andybest]

I have added an implementation for init(contentsOfFile:usedEncoding:)

After discussion on the mailing list, it was determined that the original implementation:

1. Checks extended file attributes for "com.apple.TextEncoding", and uses the encoding there.
2. If that doesn't exist, it checks the first few bytes of the data for a Byte Order Mark (BOM).
3. If there is no BOM present, just try to decode as UTF8.

I also noticed that the init(contentsOf:usedEncoding:) initializer only looked for UTF16 BOMs, so I have updated the implementation for that too.

I have added some tests for the BOM detection, and updated the status document accordingly.

[parkera]

This seems more like a fatal error than an NSError here.

[andybest]

Which one, the bridging? I was going by other code that handled the same thing- I can convert to a fatal error if that's preferred.

[parkera]

@swift-ci please test

[parkera]

Looks pretty good, thanks for taking this one.

[pushkarnk]

Foundation/NSString.swift:1396:24: error: use of unresolved identifier 'getxattr'
        let bufCount = getxattr(path, attrName, nil, 0, 0, 0)
                       ^~~~~~~~

[andybest]

I forgot to add include GLibc to my commit. I'll add it and fix the merge conflicts

[andybest]

Ok, looks like the module map for Glibc doesn't include sys/xattr.h, so I've enabled the xattr check only for MacOS for now. I will add the include to the modulemap in the Swift project and do a PR over there to get it included, then I will make a separate PR here to re-enable this functionality under Linux.

I believe this PR should be ready to go here, in any case :)

Would it be possible to re-test this PR?

[ianpartridge]

Hi @andybest did you open a PR against the Glibc modulemap? Just wondering where we're up to with this PR 😃

[alblue]

@swift-ci please test

[andybest]

@ianpartridge Apologies, I've been away and haven't had the chance- I will sort this out today :)

EDIT: I have now submitted the PR against the Glibc modulemap :)

[andybest]

By the way, this PR can be merged as-is, since there is an '#if os(' block around the missing functionality which can removed later

[ianpartridge]

@swift-ci please test

[alblue]

There were test failures on this run:

Test Case 'TestNSString.test_FromContentsOfFileUsedEncodingUTF32LEBOM' started at 2017-07-28 22:48:00.244
TestFoundation/TestNSString.swift:381: error: TestNSString.test_FromContentsOfFileUsedEncodingUTF32LEBOM : failed - URL for NSString-UTF32-LE-data.txt is nil
Test Case 'TestNSString.test_FromContentsOfFileUsedEncodingUTF32LEBOM' failed (0.0 seconds)
Test Case 'TestNSString.test_FromContentsOfFileUsedEncodingUTF32BEBOM' started at 2017-07-28 22:48:00.244
TestFoundation/TestNSString.swift:400: error: TestNSString.test_FromContentsOfFileUsedEncodingUTF32BEBOM : failed - URL for NSString-UTF32-BE-data.txt is nil

Did those files get added correctly?

[spevans]

Do the tests in the PR pass in Xcode? I noticed the tests for the UTF16 LE/BE were failing the other day and I was wondering if this fixes them as well?

[alblue]

This pull request seems to duplicate info in pull #928. Can you rebase and resubmit if necessary?

#928

[alblue]

This pull request has gone stale, closing. Please rebase and reopen if desired. See also #928