WIP: Generate docs from macros.

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Which issue does this PR close?

Closes #.

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

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@Omega359 @alamb I tried to play with custom attributes to wrap up the documentation on top of the what @Omega359 already built. I'm experimenting with just 2 fields(description and examples) and the attribute has to be placed on top of the struct.

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pre macros needed to have Documentation structure already precreated

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here we put the documentation

[alamb]

This looks quite cool ❤️

One thing I would be interested in seeing is if/how a multi line description and example would look. I have had trouble with multi-line macro / docs in the past

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and the test shows it applied

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WDYT should we move in this direction?

[Omega359]

I find this intriguing and technically very interesting! I do have a few questions:

• What are you goals with this? I am assuming cleaner looking/easier to create docs. If so I would wonder how it would help in cases were there is significant amounts of docs vs boilerplate such as in the to_date udf.
• Can it be made to handle n arguments?
• Is it possible to generate rustdoc with this approach?
• I noticed that this approach creates a Documentation object on every call. It's obviously pretty minor but it would be nice if it could be static.

To me in general while I find this quite interesting I wonder if the benefit outweighs the added complexity of the code generation. To be clear I am absolutely not against this approach - I just have a few concerns.

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I find this intriguing and technically very interesting! I do have a few questions:

• What are you goals with this? I am assuming cleaner looking/easier to create docs. If so I would wonder how it would help in cases were there is significant amounts of docs vs boilerplate such as in the to_date udf.
• Can it be made to handle n arguments?
• Is it possible to generate rustdoc with this approach?
• I noticed that this approach creates a Documentation object on every call. It's obviously pretty minor but it would be nice if it could be static.

To me in general while I find this quite interesting I wonder if the benefit outweighs the added complexity of the code generation. To be clear I am absolutely not against this approach - I just have a few concerns.

Thanks @Omega359
The idea is to reuse your current approach but make it on the level of custom Rust attribute instead of having the documentation directly in the code. So the steps can look like:

• Move Documentation structure to pre-macros crate
• generate the code from macros instead of having it statically
• we can have it static everything will be the same as its now, the only difference is the code will be created through the macros.

I'm planning to play with to_date function as it covers also multiline comments as @alamb mentioned

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@alamb @Omega359 please have a look on real example to_date (I still need to include argements to be called with the builder). As you can see it is the same approach as before, the only difference the documentation is set by attributes rather than code, but it generates documentation builders as before.

Btw multiline seems to be working

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I copied all Documentation structures here, added Test so as not to break everything