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Trying out Rust's proc macros by building a very basic ORM
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| use proc_macro::TokenStream; | |
| use quote::quote; | |
| use syn::{ | |
| parse_macro_input, Data::Struct, DataStruct, DeriveInput, Field, Fields::Named, FieldsNamed, | |
| Path, Type, TypePath, | |
| }; | |
| #[derive(Debug)] | |
| struct DBModel { | |
| name: String, | |
| fields: Vec<DBField>, | |
| } | |
| #[derive(Debug)] | |
| struct DBField { | |
| name: String, | |
| ty: String, | |
| } | |
| fn get_db_field(field: &Field) -> Option<DBField> { | |
| let ident = match &field.ident { | |
| Some(id) => Some(format!("{}", id)), | |
| None => { | |
| return None; | |
| } | |
| }; | |
| let ty_ident = match &field.ty { | |
| Type::Path(TypePath { | |
| path: Path { segments, .. }, | |
| .. | |
| }) => segments.first().map(|s| format!("{}", s.ident)), | |
| _ => { | |
| return None; | |
| } | |
| }; | |
| let db_field = DBField { | |
| name: ident.unwrap(), | |
| ty: ty_ident.unwrap(), | |
| }; | |
| println!("Field: {} - Type: {}", db_field.name, db_field.ty); | |
| Some(db_field) | |
| } | |
| #[proc_macro_derive(DBModel)] | |
| pub fn derive(input: TokenStream) -> TokenStream { | |
| let DeriveInput { ident, data, .. } = parse_macro_input!(input as DeriveInput); | |
| let fields = match data { | |
| Struct(DataStruct { | |
| fields: Named(FieldsNamed { ref named, .. }), | |
| .. | |
| }) => named, | |
| _ => panic!("Uhhh wat"), | |
| }; | |
| let db_model = DBModel { | |
| name: ident.to_string().to_lowercase(), | |
| fields: fields.iter().filter_map(get_db_field).collect(), | |
| }; | |
| println!("DBModel: {} - Fields: {:?}", db_model.name, db_model.fields); | |
| let fields: Vec<String> = db_model.fields.iter().map(|f| f.name.to_string()).collect(); | |
| let columns = fields.join(","); | |
| let input_fields = fields | |
| .iter() | |
| .map(|_| "?".to_string()) | |
| .collect::<Vec<String>>() | |
| .join(","); | |
| let select_string = format!("select {} from {};", &columns, &db_model.name); | |
| let insert_string = format!( | |
| "insert into {} ({}) values({});", | |
| &db_model.name, &columns, &input_fields | |
| ); | |
| let result = quote! { | |
| impl #ident { | |
| pub fn select() -> ::std::string::String { | |
| ::std::string::String::from(#select_string) | |
| } | |
| pub fn insert(&self) -> ::std::string::String { | |
| ::std::string::String::from(#insert_string) | |
| } | |
| } | |
| }; | |
| result.into() | |
| } |
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| #![allow(dead_code)] | |
| use micromacros::DBModel; | |
| #[derive(DBModel)] | |
| pub struct Book { | |
| id: u64, | |
| title: String, | |
| pages: u64, | |
| author: String, | |
| } | |
| #[test] | |
| fn gen_select() { | |
| let select_sql = Book::select(); | |
| assert_eq!("select id,title,pages,author from book;", select_sql); | |
| } | |
| #[test] | |
| fn gen_insert() { | |
| let book = Book { | |
| id: 1728, | |
| title: "My Story".to_string(), | |
| pages: 1337, | |
| author: "Jms Dnns".to_string(), | |
| }; | |
| let insert_sql = book.insert(); | |
| assert_eq!( | |
| "insert into book (id,title,pages,author) values(?,?,?,?);", | |
| insert_sql | |
| ); | |
| } |
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