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use darling::ast::{self, Style};
use darling::{FromDeriveInput, FromField, ToTokens};
use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, DeriveInput, Ident};
#[proc_macro_derive(FromRowTokioPostgres, attributes(from_row))]
pub fn derive_from_row_tokio_postgres(input: TokenStream) -> TokenStream {
derive_from_row(input, quote::format_ident!("tokio_postgres"))
}
#[proc_macro_derive(FromRowPostgres, attributes(from_row))]
pub fn derive_from_row_postgres(input: TokenStream) -> TokenStream {
derive_from_row(input, quote::format_ident!("postgres"))
}
fn derive_from_row(input: TokenStream, module: Ident) -> TokenStream {
let derive_input = parse_macro_input!(input as DeriveInput);
match try_derive_from_row(&derive_input, module) {
Ok(result) => result,
Err(err) => err.write_errors().into(),
}
}
fn try_derive_from_row(input: &DeriveInput, module: Ident) -> Result<TokenStream, darling::Error> {
let from_row_derive = DeriveFromRow::from_derive_input(input)?;
from_row_derive.generate(module)
}
#[derive(Debug, FromDeriveInput)]
#[darling(
attributes(from_row),
forward_attrs(allow, doc, cfg),
supports(struct_named)
)]
struct DeriveFromRow {
ident: syn::Ident,
generics: syn::Generics,
data: ast::Data<(), FromRowField>,
}
impl DeriveFromRow {
fn generate(self, module: Ident) -> Result<TokenStream, darling::Error> {
let ident = &self.ident;
let (impl_generics, ty_generics, where_clause) = self.generics.split_for_impl();
let fields = self
.data
.take_struct()
.ok_or_else(|| darling::Error::unsupported_shape("enum").with_span(&self.ident))?;
let fields = match fields.style {
Style::Unit => {
return Err(darling::Error::unsupported_shape("unit struct").with_span(&self.ident))
}
Style::Tuple => {
return Err(darling::Error::unsupported_shape("tuple struct").with_span(&self.ident))
}
Style::Struct => fields.fields,
};
let from_row_fields = fields
.iter()
.map(|f| f.generate_from_row(&module))
.collect::<syn::Result<Vec<_>>>()?;
let try_from_row_fields = fields
.iter()
.map(|f| f.generate_try_from_row(&module))
.collect::<syn::Result<Vec<_>>>()?;
let original_predicates = where_clause.clone().map(|w| &w.predicates).into_iter();
let mut predicates = Vec::new();
for field in fields.iter() {
let target_ty = &field.target_ty()?;
let ty = &field.ty;
predicates.push(if field.flatten {
quote! (#target_ty: postgres_from_row::FromRow)
} else {
quote! (#target_ty: for<'a> #module::types::FromSql<'a>)
});
if field.from.is_some() {
predicates.push(quote!(#ty: std::convert::From<#target_ty>))
} else if field.try_from.is_some() {
predicates.push(quote!(#ty: std::convert::From<#target_ty>))
}
}
Ok(quote! {
impl #impl_generics postgres_from_row::FromRow for #ident #ty_generics where #(#original_predicates),* #(#predicates),* {
fn from_row(row: &#module::Row) -> Self {
Self {
#(#from_row_fields),*
}
}
fn try_from_row(row: &#module::Row) -> std::result::Result<Self, #module::Error> {
Ok(Self {
#(#try_from_row_fields),*
})
}
}
}
.into())
}
}
#[derive(Debug, FromField)]
#[darling(attributes(from_row), forward_attrs(allow, doc, cfg))]
struct FromRowField {
ident: Option<syn::Ident>,
ty: syn::Type,
#[darling(default)]
flatten: bool,
try_from: Option<String>,
from: Option<String>,
}
impl FromRowField {
fn target_ty(&self) -> syn::Result<proc_macro2::TokenStream> {
if let Some(from) = &self.from {
Ok(from.parse()?)
} else if let Some(try_from) = &self.try_from {
Ok(try_from.parse()?)
} else {
Ok(self.ty.to_token_stream())
}
}
fn generate_from_row(&self, module: &Ident) -> syn::Result<proc_macro2::TokenStream> {
let ident = self.ident.as_ref().unwrap();
let str_ident = ident.to_string();
let field_ty = &self.ty;
let target_ty = self.target_ty()?;
let mut base = if self.flatten {
quote!(<#target_ty as postgres_from_row::FromRow>::from_row(row))
} else {
quote!(#module::Row::get::<&str, #target_ty>(row, #str_ident))
};
if self.from.is_some() {
base = quote!(<#field_ty as std::convert::From<#target_ty>>::from(#base));
} else if self.try_from.is_some() {
base = quote!(<#field_ty as std::convert::TryFrom<#target_ty>>::try_from(#base).expect("could not convert column"));
};
Ok(quote!(#ident: #base))
}
fn generate_try_from_row(&self, module: &Ident) -> syn::Result<proc_macro2::TokenStream> {
let ident = self.ident.as_ref().unwrap();
let str_ident = ident.to_string();
let field_ty = &self.ty;
let target_ty = self.target_ty()?;
let mut base = if self.flatten {
quote!(<#target_ty as postgres_from_row::FromRow>::try_from_row(row)?)
} else {
quote!(#module::Row::try_get::<&str, #target_ty>(row, #str_ident)?)
};
if self.from.is_some() {
base = quote!(<#field_ty as std::convert::From<#target_ty>>::from(#base));
} else if self.try_from.is_some() {
base = quote!(<#field_ty as std::convert::TryFrom<#target_ty>>::try_from(#base)?);
};
Ok(quote!(#ident: #base))
}
}