from_*(ptr, len) deprecation

[lrasinen]

From 3.9.1 release notes:

Passing iterator pairs or pointer/length pairs to parsing functions (basic_json::parse, basic_json::accept, basic_json::sax_parse, basic_json::from_cbor, basic_json::from_msgpack, basic_json::from_ubjson, basic_json::from_bson) via initializer lists is deprecated. Instead, pass the elements individually without braces.

However, the pointer/length overload is marked as deprecated at least for the from_* functions:

    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_cbor(ptr, ptr + len))
    JSON_HEDLEY_WARN_UNUSED_RESULT
    static basic_json from_cbor(const T* ptr, std::size_t len, ...

Is this an error in the release notes or is the deprecation in error?

[nlohmann]

You mean the version number?

[lrasinen]

My understanding of the release note wording is that e.g. from_cbor({ptr, len}) is deprecated, but that from_cbor(ptr, len) is the recommended alternative. But the second form is also deprecated.

[gregmarr]

The recommended alternative is not from_cbor(ptr, len) but from_cbor(ptr, ptr + len, ...).

[gregmarr]

@nlohmann Probably good to update the deprecation notice to include that one as well, as it's not really covered by the current note.

[lrasinen]

Agreed. My experience with this was something like this:

• I got some binary data in ptr/len format
• Went looking at the API whether that's supported directly
• Found Doxygen docs, which do not show the deprecation status
• Was baffled at compile warning
• Went looking at the release notes which were unclear

I can (and do) use the ptr/ptr+len overload instead (although the ptr/len combo is quite convenient when applicable).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[nlohmann]

Sorry for not reacting earlier. In order to clean the API after a lot of experimenting with how to cope with different input types, we decided that the overload that takes two iterators is the one we would like to proceed with.

The release notes are indeed misleading. They should read:

This release deprecates passing iterator pairs or pointer/length pairs to parsing functions (basic_json::parse, basic_json::accept, basic_json::sax_parse, basic_json::from_cbor, basic_json::from_msgpack, basic_json::from_ubjson, basic_json::from_bson) via initializer lists. Instead, pass two iterators; for instance, call basic_json::from_cbor(ptr, ptr+len) instead of basic_json::from_cbor({ptr, len}).

@lrasinen @gregmarr Do you agree with the new wording of the last sentence?

[lrasinen]

I'm quite happy with suggested wording, thanks.

[nlohmann]

I adjusted the release notes of version 3.8.0, 3.9.0, and 3.9.1.