113 lines
3.5 KiB
Rust
113 lines
3.5 KiB
Rust
use crate::utils::{DeriveType, HashMap};
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use crate::utils::{SingleFieldData, State};
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use proc_macro2::TokenStream;
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use quote::quote;
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use syn::{parse::Result, DeriveInput};
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/// Provides the hook to expand `#[derive(FromStr)]` into an implementation of `FromStr`
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pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
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let state = State::new(input, trait_name, trait_name.to_lowercase())?;
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if state.derive_type == DeriveType::Enum {
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Ok(enum_from(input, state, trait_name))
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} else {
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Ok(struct_from(&state, trait_name))
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}
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}
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pub fn struct_from(state: &State, trait_name: &'static str) -> TokenStream {
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// We cannot set defaults for fields, once we do we can remove this check
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if state.fields.len() != 1 || state.enabled_fields().len() != 1 {
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panic_one_field(trait_name);
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}
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let single_field_data = state.assert_single_enabled_field();
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let SingleFieldData {
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input_type,
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field_type,
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trait_path,
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casted_trait,
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impl_generics,
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ty_generics,
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where_clause,
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..
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} = single_field_data.clone();
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let initializers = [quote! { #casted_trait::from_str(src)? }];
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let body = single_field_data.initializer(&initializers);
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quote! {
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#[automatically_derived]
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impl #impl_generics #trait_path for #input_type #ty_generics #where_clause {
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type Err = <#field_type as #trait_path>::Err;
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#[inline]
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fn from_str(src: &str) -> derive_more::core::result::Result<Self, Self::Err> {
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derive_more::core::result::Result::Ok(#body)
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}
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}
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}
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}
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fn enum_from(
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input: &DeriveInput,
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state: State,
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trait_name: &'static str,
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) -> TokenStream {
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let mut variants_caseinsensitive = HashMap::default();
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for variant_state in state.enabled_variant_data().variant_states {
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let variant = variant_state.variant.unwrap();
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if !variant.fields.is_empty() {
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panic!("Only enums with no fields can derive({trait_name})")
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}
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variants_caseinsensitive
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.entry(variant.ident.to_string().to_lowercase())
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.or_insert_with(Vec::new)
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.push(variant.ident.clone());
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}
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let input_type = &input.ident;
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let input_type_name = input_type.to_string();
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let mut cases = vec![];
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// if a case insensitive match is unique match do that
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// otherwise do a case sensitive match
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for (ref canonical, ref variants) in variants_caseinsensitive {
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if variants.len() == 1 {
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let variant = &variants[0];
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cases.push(quote! {
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#canonical => #input_type::#variant,
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})
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} else {
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for variant in variants {
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let variant_str = variant.to_string();
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cases.push(quote! {
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#canonical if(src == #variant_str) => #input_type::#variant,
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})
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}
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}
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}
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let trait_path = state.trait_path;
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quote! {
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impl #trait_path for #input_type {
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type Err = derive_more::FromStrError;
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#[inline]
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fn from_str(src: &str) -> derive_more::core::result::Result<Self, Self::Err> {
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Ok(match src.to_lowercase().as_str() {
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#(#cases)*
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_ => return Err(derive_more::FromStrError::new(#input_type_name)),
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})
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}
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}
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}
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}
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fn panic_one_field(trait_name: &str) -> ! {
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panic!("Only structs with one field can derive({trait_name})")
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}
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