Our tool will have two modules with a data structure. The first is the src/schema.rs module, which contains a table! macro call that declares the fields of every table. In our case, this module contains the following declaration:

table! {
    users (id) {
        id -> Text,
        name -> Text,
        email -> Text,
    }
}

This file was automatically generated by the diesel setup command. When you run a setup, it creates a diesel.toml configuration file with the following contents:

# For documentation on how to configure this file,
# see diesel.rs/guides/configuring-diesel-cli
[print_schema]
file = "src/schema.rs"

As you can see, the config has a schema module reference. A schema.rs file is also generated, and will be updated on every compilation. The table! macro creates the required declaration of DSL for the tables used.