https://codeberg.org/unobtanium/criterium/src/branch/main/src/sql/schema_macro.rs

Huge Thank You goes to @steffo@a.junimo.party :drgn_heart:

Each repetition in the transcriber must contain at least one metavariable to decide how many times to expand it.

The optional comma could just be eaten by a $(…),* $(,)?

Or am I missing something? (I don't write a lot of macros.)

    enum Mimetype = "mimetype" {
        Charset = "charset"
    }

but this would give a weird error

    enum Mimetype = "mimetype" {
        Charset = "charset",
    }

Given that I can almost 1:1 copy this into criterium (licensed LGPL-3.0-only): May I? If yes, what name do you want in the copyright header?

pub trait Table {
    fn sql_safe_table_name(&self) -> &'static str;
}

pub trait Field {
    fn sql_safe_field_name(&self) -> &'static str;
}

macro_rules! sql_schema {
    {
        $schema_name:ident,
        $(
            enum $table_name:ident = $table_value:literal {
                $( $field_name:ident = $field_value:literal ),*
            }
        )*
    } => {
        pub enum $schema_name {
            $( $table_name ),*
        }

        impl Table for $schema_name {
            fn sql_safe_table_name(&self) -> &'static str {
                match self {
                    $( $schema_name::$table_name => $table_value ),*
                }
            }
        }

        $(
            // it's not possible to concatenate things to identifiers without the use of a proc macro
            // so we just re-use $table_name
            pub enum $table_name {
                $( $field_name ),*
            }

            impl Field for $table_name {
                fn sql_safe_field_name(&self) -> &'static str {
                    match self {
                        $( $table_name::$field_name => $field_value ),*
                    }
                }
            }
        )*
    }
}

sql_schema! {
    BaseTable,
    enum MimeParameter = "mime_parameter" {
        Key = "key",
        MimeParameterId = "mime_parameter_id"
    }
    enum Mimetype = "mimetype" {
        Charset = "charset"
         // …
    }
}

you can use cargo expand to see what it generates

The Declaration for my example would be:

sql_schema!{
    BaseTable
    enum MimeParameter = "mime_parameter" {
         Key = "key",
         MimeParameterId = "mime_parameter_id",
         // …
    }
    enum Mimetype = "mimetype" {
         // …
    }
    enum Origin = "origin" {
        // …
    }
    // …
}

shouldn't be an issue because in one case they're enums names and in the other they're enum variants, and the two can be disambiguated

I've noticed, that I forgot to link a file, this one is where everything gets tied together:

https://codeberg.org/unobtanium/unobtanium/src/branch/main/lib-unobtanium/src/database/schemas.rs

like

Key,
MimeParameterId,
MimetypeId,
Value,

And now that you'Re asking I actually have an example implementation (generated by a lua script):

• https://codeberg.org/unobtanium/unobtanium/src/branch/main/lib-unobtanium/src/database/tables.rs
• https://codeberg.org/unobtanium/unobtanium/src/branch/main/lib-unobtanium/src/database/fields.rs