Feature Request: `<Before|After><Insert|Update|Delete>Hook`

[tamaro-skaljic]

Instead of

• telling all my colleagues to always remember to call a custom insert, update or delete helper function which uses ctx.db.<table> .<action>() or .<index>().<action>() and does something before and/or afterwards (in server module code) rather than using ctx.db directly (because the logic executed before/after it in the helper function is crucial for e.g. referential integrity, authorization, etc.),

I want to

• hook into SpacetimeDBs `<insert|update|upsert|delete> functionality so that SpacetimeDB makes sure that it's happening.

Proposed API:

// Position table struct omitted…

/// Before Insert Hooks allow validating or changing rows before insertion
#[spacetimedb::hook(
    moment = before,
    action = insert,
    table = position,
)]
pub fn before_position_insert(
    ctx: &TxContext,
    new_position: Position,
) -> Result<Position, impl Display>;

/// After Insert Hooks allow to react on row insertions
#[spacetimedb::hook(
    moment = after,
    action = insert,
    table = position,
)]
pub fn after_position_insert(
    ctx: &TxContext,
    new_position: &Position,
) -> Result<(), impl Display>;

/// Before Update Hooks allow validating or changing rows before modification
#[spacetimedb::hook(
    moment = before,
    action = update,
    table = position,
)]
pub fn before_position_update(
    ctx: &TxContext,
    old_position: &Position,
    new_position: Position,
) -> Result<Position, impl Display>;

/// After Update Hooks allow to react on row modifications
#[spacetimedb::hook(
    moment = after,
    action = update,
    table = position,
)]
pub fn after_position_update(
    ctx: &TxContext,
    old_position: &Position,
    new_position: &Position,
) -> Result<(), impl Display>;

/// Before Delete Hooks allow validating before deletion
#[spacetimedb::hook(
    moment = before,
    action = delete,
    table = position,
)]
pub fn before_position_delete(
    ctx: &TxContext,
    old_positions: &Vec<Position>,
) -> Result<(), impl Display>;

/// After Delete Hooks allow to react on row deletions
#[spacetimedb::hook(
    moment = after,
    action = delete,
    table = position,
)]
pub fn after_position_delete(
    ctx: &TxContext,
    old_positions: Vec<Position>,
) -> Result<(), impl Display>;

Currently implemented in https://github.com/tamaro-skaljic/SpacetimeDSL/blob/main/docs/DOCUMENTATION.md#hooks-system

[cloutiertyler]

This is related to middleware as well.