google-cloud-spanner-derive 0.2.0

//! # google-cloud-spanner-derive
//!
//! Procedural macro for [google-cloud-spanner](../spanner).
//!
//! ## Quick Start
//!
//! ### Table derive
//!
//! `#[derive(Table)]` generates the implementation for following traits.
//! * `TryFromStruct`
//! * `ToStruct`
//! * `TryFrom<Row>`
//!
//! ```
//! use time::OffsetDateTime;
//! use google_cloud_spanner::client::{Client,Error};
//! use google_cloud_spanner::mutation::insert_struct;
//! use google_cloud_spanner::reader::AsyncIterator;
//! use google_cloud_spanner::statement::Statement;
//! use google_cloud_spanner_derive::Table;
//!
//! #[derive(Table)]
//! pub struct UserCharacter {
//!     pub user_id: String,
//!     pub character_id: i64,
//!     // #[spanner(name=...) is used when the column name does not appear in camel case of the field name
//!     #[spanner(name="LevelX")]
//!     pub level: i64,
//!     #[spanner(commitTimestamp)]
//!     pub updated_at: OffsetDateTime,
//! }
//!
//! impl Default for UserCharacter {
//!     fn default() -> Self {
//!         Self {
//!             user_id: Default::default(),
//!             character_id: Default::default(),
//!             level: Default::default(),
//!             updated_at: OffsetDateTime::UNIX_EPOCH,
//!         }
//!     }
//! }
//!
//! async fn run(client: &Client) -> Result<Vec<UserCharacter>, Error> {
//!     let user = UserCharacter {
//!         user_id: "user_id".to_string(),
//!         ..Default::default()
//!     };
//!     client.apply(vec![insert_struct("UserCharacter", user)]).await?;
//!
//!     let mut tx = client.read_only_transaction().await?;
//!     let stmt = Statement::new("SELECT * From UserCharacter Limit 10");
//!     let mut reader = tx.query(stmt).await?;
//!     let mut result = vec![];
//!     while let Some(row) = reader.next().await? {
//!         result.push(row.try_into()?);
//!     }
//!     Ok(result)
//! }
//!```
//!
//! Here is the generated implementation.
//!```
//! use time::OffsetDateTime;
//! use google_cloud_spanner::statement::{ToStruct, ToKind, Kinds, Types};
//! use google_cloud_spanner::row::{Struct, TryFromValue, TryFromStruct, Row, Error as RowError};
//! use google_cloud_spanner::value::CommitTimestamp;
//! use std::convert::TryFrom;
//!
//! pub struct UserCharacter {
//!     pub user_id: String,
//!     pub character_id: i64,
//!     pub level: i64,
//!     pub updated_at: OffsetDateTime,
//! }
//!
//! impl ToStruct for UserCharacter {
//!     fn to_kinds(&self) -> Kinds {
//!         vec![
//!             ("UserId", self.user_id.to_kind()),
//!             ("CharacterId", self.character_id.to_kind()),
//!             ("LevelX", self.level.to_kind()),
//!             ("UpdatedAt", self.updated_at.to_kind()),
//!         ]
//!     }
//!
//!    fn get_types() -> Types {
//!        vec![
//!           ("UserId", String::get_type()),
//!            ("CharacterId", i64::get_type()),
//!            ("LevelX", i64::get_type()),
//!            ("UpdatedAt", CommitTimestamp::get_type()),
//!        ]
//!    }
//! }
//!
//! impl TryFromStruct for UserCharacter {
//!    fn try_from_struct(s: Struct<'_>) -> Result<Self, RowError> {
//!        Ok(UserCharacter {
//!            user_id: s.column_by_name("UserId")?,
//!            character_id: s.column_by_name("CharacterId")?,
//!            level: s.column_by_name("LevelX")?,
//!            updated_at: s.column_by_name("UpdatedAt")?,
//!        })
//!    }
//! }
//!
//! impl TryFrom<Row> for UserCharacter {
//!    type Error = RowError;
//!    fn try_from(s: Row) -> Result<Self, RowError> {
//!        Ok(UserCharacter {
//!            user_id: s.column_by_name("UserId")?,
//!            character_id: s.column_by_name("CharacterId")?,
//!            level: s.column_by_name("LevelX")?,
//!            updated_at: s.column_by_name("UpdatedAt")?,
//!        })
//!    }
//! }
//!```
//!
//! ### Query derive
//!
//! `#[derive(Query)]` generates the implementation for following traits.
//! * `TryFrom<Row>`
//!
//!```
//! use google_cloud_spanner::transaction::Transaction;
//! use google_cloud_spanner::reader::AsyncIterator;
//! use google_cloud_spanner::client::{Client, Error};
//! use google_cloud_spanner::statement::Statement;
//! use google_cloud_spanner_derive::{Table, Query};
//!
//! #[derive(Table, Default)]
//! pub struct UserCharacter {
//!     pub user_id: String,
//!     pub character_id: i64,
//! }
//!
//! #[derive(Table, Default)]
//! pub struct UserItem {
//!     pub user_id: String,
//!     pub item_id: i64,
//! }
//!
//! #[derive(Query, Default)]
//! pub struct UserBundle {
//!    pub user_id: String,
//!    pub user_characters: Vec<UserCharacter>,
//!    #[spanner(name="Items")]
//!    pub user_items: Vec<UserItem>
//! }
//!
//! async fn run(user_id: &str, tx: &mut Transaction) -> Result<Option<UserBundle>, Error> {
//!    let mut stmt = Statement::new("
//!        SELECT
//!            UserId,
//!            ARRAY(SELECT AS STRUCT * FROM UserCharacter WHERE UserId = @UserId) AS UserCharacters,
//!            ARRAY(SELECT AS STRUCT * FROM UserItem WHERE UserId = @UserId) AS Items,
//!        From User WHERE UserID = @UserID",
//!    );
//!    stmt.add_param("UserID", &user_id);
//!    let mut reader = tx.query(stmt).await?;
//!    match reader.next().await? {
//!        Some(row) => Ok(Some(row.try_into()?)),
//!        None => Ok(None)
//!    }
//! }
//! ```

use proc_macro::TokenStream;

use quote::{quote, ToTokens};
use syn::{parse_macro_input, ItemStruct};

mod column;
mod query;
mod symbol;
mod table;

#[proc_macro_derive(Table, attributes(spanner))]
pub fn table(input: TokenStream) -> TokenStream {
    let item = parse_macro_input!(input as ItemStruct);
    let table = table::generate_table_methods(item.clone());
    let query = query::generate_query_methods(item);
    wrap_in_dummy_mod(quote! {
        #table
        #query
    })
}

#[proc_macro_derive(Query, attributes(spanner))]
pub fn query(input: TokenStream) -> TokenStream {
    let item = parse_macro_input!(input as ItemStruct);
    let query = query::generate_query_methods(item);
    wrap_in_dummy_mod(query)
}

fn wrap_in_dummy_mod(item: impl ToTokens) -> TokenStream {
    //reference https://github.com/diesel-rs/diesel/blob/94599bdc86692900c888974bb4a03568799978d3/diesel_derives/src/util.rs
    let wrapped = quote! {
        #[allow(unused_imports)]
        const _: () = {
            use google_cloud_spanner::statement::{ToStruct, ToKind, Kinds, Types};
            use google_cloud_spanner::row::{Struct, TryFromValue, TryFromStruct, Row, Error as RowError};
            use google_cloud_spanner::value::CommitTimestamp;
            use std::convert::TryFrom;

            #item
        };
    };
    wrapped.into()
}