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Detect XN-Labels case-insensitively #636
Detect XN-Labels case-insensitively #636
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Punycode is relatively complex and I do believe that coercing the entire label into lowercase does have implications on the output string. Take the following (playground link) which borrows from Wikipedia's Punycode::Examples table
Here we have a label which has an ASCII literal embedded in it (the
O
ando
) which ends up coming out of the other end raw.There was a problem hiding this comment.
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Thanks @christopher-henderson. Your suggestion of creating reusable IDNA functions is definitely cleaner than my original proposal. I went ahead and incorporated your suggested implementation with some small changes.
In regard to case-sensitivity, the two lints that currently use ToUnicode won't have different results if the label is downcased (https://datatracker.ietf.org/doc/html/rfc3492#appendix-A), but the reusable functions definitely should preserve casing as you pointed out as returning a downcased U-label would be surprising API behavior.
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That appendix, however, is not mandatory.
And besides, the link to the Go playground code snippet clearly shows that this particular implementation does in fact get different answers in some cases depending on the casing.
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@christopher-henderson Regarding
and
The point of that is that the mixed case preservation is the optional aspect, and purely a presentational decision. The appendix describes how one can preserve cases in the encoded string, in order to have it reflected in the display, but the underlying functions are insensitive.
With respect to host names (i.e. those for A and AAAA), we unambiguously know that they are case insensitive.
I may be misreading the comments here, but it should be unambiguous that