"ignore struct length" flag

[Ponywka]

In some scenarios, it is necessary to ignore the structure length.

One such example is Tarantool. Due to the specifics of the Lua language, a structure that has an empty value at the end (for example, {0, nil, 1, 2, nil}) is truncated to the last non-nil value and becomes {0, nil, 1, 2}.

More details are available in the Tarantool documentation.

Despite this behavior, the official Go module github.com/tarantool/go-tarantool/v2 still uses the github.com/vmihailenco/msgpack module in the decoder (see here), which reports an error in such cases:
msgpack: number of fields in array-encoded struct has changed.

This PR introduces an option to ignore this error and also fixes decoding when the number of fields differs from what is defined in the struct.

[xe-nvdk]

Hi @Ponywka, this looks useful for Tarantool compatibility. This repo has been unmaintained for ~3 years so PRs have been sitting without review.

We maintain an active fork at github.com/Basekick-Labs/msgpack (v6) that's a drop-in replacement. We don't have this flag yet but it's a reasonable addition — if you're interested, we'd welcome a PR to the fork. Happy to review.

[Ponywka]

@xe-nvdk

We maintain an active fork at github.com/Basekick-Labs/msgpack (v6) that's a drop-in replacement. We don't have this flag yet but it's a reasonable addition — if you're interested, we'd welcome a PR to the fork. Happy to review.

I will do it later when I get off work