feat!: Expose on_delete and on_update fields for ForeignKey field

[ElijahAhianyo]

Related issue or discussion

Fixes #540

Description

The code example below:

#[model]
#[derive(Debug, Clone)]
pub struct Customer {
    #[model(primary_key)]
    id: Auto<i64>,
}

#[model]
#[derive(Debug, Clone)]
pub struct Product {
    #[model(primary_key)]
    id: Auto<i64>,
}

#[model]
#[derive(Debug, Clone)]
pub struct Order {
    #[model(primary_key)]
    id: Auto<i64>,
    #[model(foreign_key(on_delete = "cascade"))]
    customer: ForeignKey<Customer>,
    #[model(foreign_key(on_delete = "cascade", on_update = "set_none"))]
    product: Option<ForeignKey<Product>>,
}

Generates the migration file below:

#[derive(Debug, Copy, Clone)]
pub(super) struct Migration;
impl ::cot::db::migrations::Migration for Migration {
    const APP_NAME: &'static str = "playground";
    const MIGRATION_NAME: &'static str = "m_0002_auto_20260519_011613";
    const DEPENDENCIES: &'static [::cot::db::migrations::MigrationDependency] = &[
        ::cot::db::migrations::MigrationDependency::migration("playground", "m_0001_initial"),
    ];
    const OPERATIONS: &'static [::cot::db::migrations::Operation] = &[
        ::cot::db::migrations::Operation::create_model()
            .table_name(::cot::db::Identifier::new("playground__product"))
            .fields(
                &[
                    ::cot::db::migrations::Field::new(
                            ::cot::db::Identifier::new("id"),
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::TYPE,
                        )
                        .set_null(
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::NULLABLE,
                        )
                        .auto()
                        .primary_key(),
                ],
            )
            .build(),
        ::cot::db::migrations::Operation::create_model()
            .table_name(::cot::db::Identifier::new("playground__customer"))
            .fields(
                &[
                    ::cot::db::migrations::Field::new(
                            ::cot::db::Identifier::new("id"),
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::TYPE,
                        )
                        .set_null(
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::NULLABLE,
                        )
                        .auto()
                        .primary_key(),
                ],
            )
            .build(),
        ::cot::db::migrations::Operation::create_model()
            .table_name(::cot::db::Identifier::new("playground__order"))
            .fields(
                &[
                    ::cot::db::migrations::Field::new(
                            ::cot::db::Identifier::new("id"),
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::TYPE,
                        )
                        .set_null(
                            <cot::db::Auto<i64> as ::cot::db::DatabaseField>::NULLABLE,
                        )
                        .auto()
                        .primary_key(),
                    ::cot::db::migrations::Field::new(
                            ::cot::db::Identifier::new("customer"),
                            <cot::db::ForeignKey<
                                crate::Customer,
                            > as ::cot::db::DatabaseField>::TYPE,
                        )
                        .set_null(
                            <cot::db::ForeignKey<
                                crate::Customer,
                            > as ::cot::db::DatabaseField>::NULLABLE,
                        )
                        .foreign_key(
                            <crate::Customer as ::cot::db::Model>::TABLE_NAME,
                            <crate::Customer as ::cot::db::Model>::PRIMARY_KEY_NAME,
                            ::cot::db::ForeignKeyOnDeletePolicy::Cascade,
                            ::cot::db::ForeignKeyOnUpdatePolicy::Cascade,
                        ),
                    ::cot::db::migrations::Field::new(
                            ::cot::db::Identifier::new("product"),
                            <Option<
                                cot::db::ForeignKey<crate::Product>,
                            > as ::cot::db::DatabaseField>::TYPE,
                        )
                        .set_null(
                            <Option<
                                cot::db::ForeignKey<crate::Product>,
                            > as ::cot::db::DatabaseField>::NULLABLE,
                        )
                        .foreign_key(
                            <crate::Product as ::cot::db::Model>::TABLE_NAME,
                            <crate::Product as ::cot::db::Model>::PRIMARY_KEY_NAME,
                            ::cot::db::ForeignKeyOnDeletePolicy::Cascade,
                            ::cot::db::ForeignKeyOnUpdatePolicy::SetNone,
                        ),
                ],
            )
            .build(),
    ];
}

#[derive(::core::fmt::Debug)]
#[::cot::db::model(model_type = "migration")]
struct _Customer {
    #[model(primary_key)]
    id: cot::db::Auto<i64>,
}
#[derive(::core::fmt::Debug)]
#[::cot::db::model(model_type = "migration")]
struct _Order {
    #[model(primary_key)]
    id: cot::db::Auto<i64>,
    #[model(foreign_key(on_delete = "cascade"))]
    customer: cot::db::ForeignKey<crate::Customer>,
    #[model(foreign_key(on_delete = "cascade", on_update = "set_none"))]
    product: Option<cot::db::ForeignKey<crate::Product>>,
}
#[derive(::core::fmt::Debug)]
#[::cot::db::model(model_type = "migration")]
struct _Product {
    #[model(primary_key)]
    id: cot::db::Auto<i64>,
}

Type of change

• Bug fix
• New feature
• Documentation
• Refactor / cleanup
• Performance improvement
• Other (describe above)

[github-actions]

Bencher Report

Branch	elijah/fk-on-delete-on-update
Testbed	github-ubuntu-latest

Click to view all benchmark results

Benchmark	Latency	Benchmark Result microseconds (µs) (Result Δ%)	Upper Boundary microseconds (µs) (Limit %)
empty_router/empty_router	📈 view plot 🚷 view threshold	5,722.60 µs (-6.37%) Baseline: 6,111.63 µs	7,723.65 µs (74.09%)
json_api/json_api	📈 view plot 🚷 view threshold	996.86 µs (-7.30%) Baseline: 1,075.40 µs	1,324.49 µs (75.26%)
nested_routers/nested_routers	📈 view plot 🚷 view threshold	934.14 µs (-5.98%) Baseline: 993.60 µs	1,204.82 µs (77.53%)
single_root_route/single_root_route	📈 view plot 🚷 view threshold	900.52 µs (-5.83%) Baseline: 956.27 µs	1,168.37 µs (77.07%)
single_root_route_burst/single_root_route_burst	📈 view plot 🚷 view threshold	17,079.00 µs (-3.43%) Baseline: 17,685.14 µs	21,147.11 µs (80.76%)

🐰 View full continuous benchmarking report in Bencher

[codecov]

Codecov Report

❌ Patch coverage is 97.74011% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cot-codegen/src/model.rs	96.99%	3 Missing and 1 partial ⚠️

Flag	Coverage Δ
rust	90.36% <97.74%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cot-cli/src/migration_generator.rs	89.61% <100.00%> (+0.52%)	⬆️
cot-macros/src/lib.rs	94.84% <ø> (ø)
cot/src/db.rs	86.83% <ø> (ø)
cot-codegen/src/model.rs	95.57% <96.99%> (+0.88%)	⬆️

... and 1 file with indirect coverage changes

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[seqre]

LGTM