lasantosr/model-mapper

just did a deep dive on this before deciding whether to add it to a project. read through the source, traced the macro output by hand, went through all the examples.

the nested container hints are the standout feature. opt(iter(opt)) mapping Option<Vec<Option<i32>>> to Option<Vec<Option<i64>>> in one annotation is genuinely useful and nothing else i found handles it as cleanly.

the custom function escape hatch is well thought out too. when From can't express what you need, it generates a named method instead of trying to force a trait impl. that's the right instinct.

two things gave me pause. TryFrom is hardcoded to anyhow::Error with no way to configure it, which is a real constraint if your codebase uses a different error type. and there's no actual test suite, just example files with asserts in main(). for a proc-macro that generates code invisibly, i'd want more coverage before fully trusting it.

going to try it on a smaller layer first and see how it holds up.