[Issue 17553] std.json invalid utf8 sequence

Jun 26, 2017

Vladimir Panteleev

June 26, 2017

Posted by Vladimir Panteleev

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Vladimir Panteleev

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https://issues.dlang.org/show_bug.cgi?id=17553

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dlang-bugzilla@thecybershad
                   |                            |ow.net
         Resolution|---                         |INVALID

--- Comment #1 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> ---
As far as Phobos (and some parts of the language itself) are concerned, D strings are expected to be UTF-encoded, i.e. contain a valid stream of UTF characters. Your program elides that assumption by using a cast - the normal way to read text data into a string is the readText function, which does UTF validation. When using readText, reading a file which does not contain valid UTF will result in an exception being thrown.

As for JSON encoding - although most of JSON transformations concern themselves with just the ASCII part, the JSON standard does forbid encoding Unicode control characters, which may appear in a valid D string but must not appear in a JSON-encoded one. This includes the high control characters (code points 0x80 to 0x9F); so, the encoding code must check for these code points when constructing the JSON string. Although they could in theory be special cased, the most straight-forward way to do it is to look at the input string as a range of Unicode code points (dchars), i.e. rely on auto-decoding, which is what the current implementation does.

In any case, JSON strings are certainly not meant to store binary data - even if the example "worked" (for a certain definition of "work"), the resulting JSON object will not be in any particular encoding. Even though the JSON syntax is restricted to ASCII characters, JSON itself is not - it is Unicode aware, and contains instructions on how to properly encode and decode Unicode characters, so it can't be used for storing arbitrary binary data.

If you have a specific use case in mind which is in line with the JSON spec and how D deals with Unicode and strings, please reopen; otherwise, there is no actionable defect presented in this issue.

--

https://issues.dlang.org/show_bug.cgi?id=17553 Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|INVALID |--- Summary|std.json invalid utf8 |std.json should not do UTF |sequence |decoding when encoding JSON --- Comment #2 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> --- RFC 7159 specifies that Unicode control characters don't need escaping, so actually we can avoid auto-decoding when encoding JSON. --

https://issues.dlang.org/show_bug.cgi?id=17553 --- Comment #3 from github-bugzilla@puremagic.com --- Commit pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/5031ff1446f58a4a76e16d76aa80329d1981cb32 Fix Issue 17553 - std.json should not do UTF decoding when encoding JSON --

https://issues.dlang.org/show_bug.cgi?id=17553 --- Comment #4 from github-bugzilla@puremagic.com --- Commit pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/5031ff1446f58a4a76e16d76aa80329d1981cb32 Fix Issue 17553 - std.json should not do UTF decoding when encoding JSON --

https://issues.dlang.org/show_bug.cgi?id=17553 --- Comment #5 from github-bugzilla@puremagic.com --- Commit pushed to dmd-cxx at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/5031ff1446f58a4a76e16d76aa80329d1981cb32 Fix Issue 17553 - std.json should not do UTF decoding when encoding JSON --

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