Add options to configure how traits are rendered in Rust

[lorisleiva]

This PR adds the following TraitOptions configuration object to the Rust renderer allowing users to tweak how traits are rendered in their clients.

export type TraitOptions = {
    /** The default traits to implement for all types. */
    baseDefaults?: string[];
    /**
     * The default traits to implement for data enums only — on top of the base defaults.
     * Data enums are enums with at least one non-unit variant.
     */
    dataEnumDefaults?: string[];
    /**
     * The mapping of feature flags to traits.
     * For each entry, the traits will be rendered within a
     * `#[cfg(feature = "feature_name", derive(Traits))]` attribute.
     */
    featureFlags?: Record<string, string[]>;
    /** The complete trait overrides of specific types. */
    overrides?: Record<string, string[]>;
    /**
     * The default traits to implement for scalar enums only — on top of the base defaults.
     * Scalar enums are enums with no variants or only unit variants.
     */
    scalarEnumDefaults?: string[];
    /** The default traits to implement for structs only — on top of the base defaults. */
    structDefaults?: string[];
    /** Whether or not to use the fully qualified name for traits, instead of importing them. */
    useFullyQualifiedName?: boolean;
};

The default values for these options are:

export const DEFAULT_TRAIT_OPTIONS: Required<TraitOptions> = {
    baseDefaults: [
        'borsh::BorshSerialize',
        'borsh::BorshDeserialize',
        'serde::Serialize',
        'serde::Deserialize',
        'Clone',
        'Debug',
        'Eq',
        'PartialEq',
    ],
    dataEnumDefaults: [],
    featureFlags: { serde: ['serde::Serialize', 'serde::Deserialize'] },
    overrides: {},
    scalarEnumDefaults: ['Copy', 'PartialOrd', 'Hash', 'num_derive::FromPrimitive'],
    structDefaults: [],
    useFullyQualifiedName: false,
};

See readme changes for more details.

[changeset-bot]

🦋 Changeset detected

Latest commit: 91cb4c8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@codama/renderers-rust	Patch
@codama/renderers	Patch

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[febo]

Looks great! Couple of micro nits on the comments/docs.

[buffalojoec]

Post-humous review here!

I love the change. I think it's going to make working with the generated types a lot easier and less restrictive. A couple of thoughts from my side:

• Technically speaking, what these configs are representing are traits that are derived on the types. There's nothing stopping developers from implementing traits on generated types in a file outside of the generated dir. I guess this would just be a naming nit then.
• Some traits often rely on other traits being implemented on the type as well. for example, bytemuck's Pod requires Copy. I think it's okay to not really worry about this hiccup, since devs can just add the trait necessary and regenerate.
• Some traits like bytemuck's Pod also require #[repr(C)]. Even without bytemuck, some types may want to use this (like enums). Should we include a config for repr?

[buffalojoec]

I think there's a case to be made for the default being zero traits and zero scalar enum configurations, but I don't feel too strongly about it.

[lorisleiva]

We had to keep them like that in order to avoid introducing breaking changes. This produces code in the exact same way we were before. But I think these are sensible defaults for most clients, right?

[buffalojoec]

Sure, it doesn't really hurt to just let people change the base defaults anyway, and avoid the breaking change.

[buffalojoec]

micro-micro-nit:

Suggested change

	Using the `traitOptions` attribute, you may configure the default traits that will be applied to every Rust type. These default traits can be configured using 4 different attributes:
	Using the `traitOptions` attribute, you may configure the default traits that will be applied to every generated Rust type. These default traits can be configured using 4 different attributes:

[buffalojoec]

Slick, I like it!

[buffalojoec]

I like this even more!

[lorisleiva]

Some traits like bytemuck's Pod also require #[repr(C)]. Even without bytemuck, some types may want to use this (like enums). Should we include a config for repr?

@buffalojoec Would this be a blocker for you right now on some programs? If not, let's wait until more people ask for it. Otherwise, we can brainstorm a new representation option inside this traitOptions object asap.

[buffalojoec]

Some traits like bytemuck's Pod also require #[repr(C)]. Even without bytemuck, some types may want to use this (like enums). Should we include a config for repr?

@buffalojoec Would this be a blocker for you right now on some programs? If not, let's wait until more people ask for it. Otherwise, we can brainstorm a new representation option inside this traitOptions object asap.

Nope, not a blocker for me. I think if anyone tries to use the new trait configs to set up bytemuck traits then they'll hit the repr problem, but we can wait for that yep.

[Dodecahedr0x]

Hello, I'm trying to use Codama with a pinocchio+bytemuck program and I'm hitting this issue of the generated code not having the #[repr(C)]