Add #[derive(ormlite::Enum)] Procedural Macro

[eboody]

This pull request introduces a new procedural macro, #[derive(ormlite::Enum)], to simplify the process of creating enums compatible with ormlite and SQLx. This macro automates the implementation of various traits for enums, such as:

• std::fmt::Display
• std::str::FromStr
• std::convert::TryFrom
• sqlx::Encode
• sqlx::Decode
• sqlx::Type

By deriving ormlite::Enum, developers can focus on defining their enums while ensuring they are ready to use with ormlite and SQLx without boilerplate code.

---

Example Usage

Before this feature, developers needed to manually implement traits for each enum:

use std::str::FromStr;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum MyEnum {
    VariantOne,
    VariantTwo,
}

impl std::fmt::Display for MyEnum { /* Implementation omitted */ }
impl std::str::FromStr for MyEnum { /* Implementation omitted */ }
// Other trait implementations...

With #[derive(ormlite::Enum)], the code becomes:

#[derive(ormlite::Enum)]
pub enum MyEnum {
    VariantOne,
    VariantTwo,
}

---

Features

• Automatically generates implementations for:
  • Display for string representations
  • FromStr for parsing strings into enum variants
  • SQLx traits (Encode, Decode, Type) for seamless database integration
• Supports snake_case conversion of enum variant names to strings.

---

Technical Details

Macro Implementation:

• Built using the proc-macro crate with dependencies on syn, quote, and proc-macro2.
• Ensures enums are safe and ergonomic for database operations.
• Internally, variants are converted to and from their snake_case string representations.

---

Impact

• Developer Experience: Reduces boilerplate code for ormlite/database-ready enums.
• Performance: Implements traits efficiently, matching manual implementations.

---

How to Use

1. Annotate enums with #[derive(ormlite::Enum)]:

   #[derive(ormlite::Enum)]
   pub enum Status {
      Active,
      Inactive,
   }

2. Use them in your ormlite::Models:

   #[derive(ormlite::Model)]
   struct Article {
      status: Status
   }

Next Steps

1. Create tests
2. Review the implementation and provide feedback.
3. Publish updated documentation for ormlite to include the new macro.
4. Tag a new release after merging.

---

Acknowledgments

Special thanks to everyone involved in designing and refining this crate! It's beautifully simple. 🎉

Closes #37

[eboody]

ok! how is this looking @kurtbuilds ?

[eboody]

bump!

[kurtbuilds]

let me get the master tests fixed this wekeend, then i'll tackle this. busy time personally as i'm moving apartments, so feel free to bump again if i don't get to it.

[eboody]

sound good! no rush dude and congrats on the move

[eboody]

bump!

[eboody]

should i keep bumping? @kurtbuilds

[eboody]

@kurtbuilds the builds are going to continue to fail until that test is addressed. i think it started happening when that builder-struct-add-derive pr was merged but i might be wrong!

should i take a stab at addressing it?

[kurtbuilds]

Thank you for the pings!

I'm fixing the test now, it's from an experimental feature I added around a month ago. I'm actually reverting that feature b/c it didn't behave as desired, and then I'll merge this in.

[eboody]

amazing! thanks @kurtbuilds

once thats addressed my other PRs should pass too

[kurtbuilds]

publishing as 0.22.8.

Thank you again!