[json][review] Scott Determan review

From: Scott Determan (scott.determan_at_[hidden])
Date: 2020-09-23 15:02:29

I recommend ACCEPTING the proposed json library.

  - What is your evaluation of the design?

Design is very good. The parser interfaces and object building interfaces
meet my needs. I especially want to call out the pmr support and it's
support for either sharing or transferring ownership of resources. It's
unfortunate that this required a non-standard string class, but I think
supporting shared ownership is worth it.

I also like the use of tag_invoke for customization points. Apart from
libunifex, this is the first library I've seen that uses this mechanism. I
think this is the right way to do customization points.

  - What is your evaluation of the implementation?

I looked at the value, storage_ptr, and object classes. It appears to be a
very high quality implementation. However, I did this only as a sanity
check, I did not spend much time looking at the implementation. The
benchmarking numbers also point to a high quality implementation.

  - What is your evaluation of the documentation?

 Documentation is very good. Message for Vinnie: One minor nit caught my
eye: My understanding is when implementing a tag_invoke customization point
it should be a hidden friend because it improves compile times by keeping
overload sets smaller. If that is best practice (and it may not be; I'm not
a tag_invoke expert), then the examples in the documentation should follow
this.

  - What is your evaluation of the potential usefulness of the library?

It covers a widely useful range of json functionality and I expect this
library to be widely used. If accepted I intend on using it immediately.

  - Did you try to use the library? With which compiler(s)? Did you have
any problems?

Yes: gcc 10.2 and clang 10.0.1; Linux; No problems.

  - How much effort did you put into your evaluation? A glance? A quick
reading? In-depth study?

 Read the documentation, browsed the code, wrote some toy programs. Spent
about half a day on it.

  - Are you knowledgeable about the problem domain?

As a library consumer, I am familiar with nlohmann_json as well as the
custom json library used in my current work project. I am not familiar with
the problem domain from a library writer point of view.