1use proc_macro::TokenStream;
  2
  3use quote::quote;
  4use syn::{
  5    Data, DeriveInput, Field, Fields, ItemEnum, ItemStruct, Type, parse_macro_input, parse_quote,
  6};
  7
  8/// Derives the `MergeFrom` trait for a struct.
  9///
 10/// This macro automatically implements `MergeFrom` by calling `merge_from`
 11/// on all fields in the struct.
 12///
 13/// # Example
 14///
 15/// ```ignore
 16/// #[derive(Clone, MergeFrom)]
 17/// struct MySettings {
 18///     field1: Option<String>,
 19///     field2: SomeOtherSettings,
 20/// }
 21/// ```
 22#[proc_macro_derive(MergeFrom)]
 23pub fn derive_merge_from(input: TokenStream) -> TokenStream {
 24    let input = parse_macro_input!(input as DeriveInput);
 25
 26    let name = &input.ident;
 27    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
 28
 29    let merge_body = match &input.data {
 30        Data::Struct(data_struct) => match &data_struct.fields {
 31            Fields::Named(fields) => {
 32                let field_merges = fields.named.iter().map(|field| {
 33                    let field_name = &field.ident;
 34                    quote! {
 35                        self.#field_name.merge_from(&other.#field_name);
 36                    }
 37                });
 38
 39                quote! {
 40                    #(#field_merges)*
 41                }
 42            }
 43            Fields::Unnamed(fields) => {
 44                let field_merges = fields.unnamed.iter().enumerate().map(|(i, _)| {
 45                    let field_index = syn::Index::from(i);
 46                    quote! {
 47                        self.#field_index.merge_from(&other.#field_index);
 48                    }
 49                });
 50
 51                quote! {
 52                    #(#field_merges)*
 53                }
 54            }
 55            Fields::Unit => {
 56                quote! {
 57                    // No fields to merge for unit structs
 58                }
 59            }
 60        },
 61        Data::Enum(_) => {
 62            quote! {
 63                *self = other.clone();
 64            }
 65        }
 66        Data::Union(_) => {
 67            panic!("MergeFrom cannot be derived for unions");
 68        }
 69    };
 70
 71    let expanded = quote! {
 72        impl #impl_generics crate::merge_from::MergeFrom for #name #ty_generics #where_clause {
 73            fn merge_from(&mut self, other: &Self) {
 74                use crate::merge_from::MergeFrom as _;
 75                #merge_body
 76            }
 77        }
 78    };
 79
 80    TokenStream::from(expanded)
 81}
 82
 83/// Registers the setting type with the SettingsStore. Note that you need to
 84/// have `gpui` in your dependencies for this to work.
 85#[proc_macro_derive(RegisterSetting)]
 86pub fn derive_register_setting(input: TokenStream) -> TokenStream {
 87    let input = syn::parse_macro_input!(input as DeriveInput);
 88    let type_name = &input.ident;
 89
 90    quote! {
 91        settings::private::inventory::submit! {
 92            settings::private::RegisteredSetting {
 93                settings_value: || {
 94                    Box::new(settings::private::SettingValue::<#type_name> {
 95                        global_value: None,
 96                        local_values: Vec::new(),
 97                    })
 98                },
 99                from_settings: |content| Box::new(<#type_name as settings::Settings>::from_settings(content)),
100                id: || std::any::TypeId::of::<#type_name>(),
101            }
102        }
103    }
104    .into()
105}
106
107// Adds serde attributes to each field with type Option<T>:
108// #serde(default, skip_serializing_if = "Option::is_none", deserialize_with = "settings::deserialize_fallible")
109#[proc_macro_attribute]
110pub fn with_fallible_options(_args: TokenStream, input: TokenStream) -> TokenStream {
111    fn apply_on_fields(fields: &mut Fields) {
112        match fields {
113            Fields::Unit => {}
114            Fields::Named(fields) => {
115                for field in &mut fields.named {
116                    add_if_option(field)
117                }
118            }
119            Fields::Unnamed(fields) => {
120                for field in &mut fields.unnamed {
121                    add_if_option(field)
122                }
123            }
124        }
125    }
126
127    fn add_if_option(field: &mut Field) {
128        match &field.ty {
129            Type::Path(syn::TypePath { qself: None, path })
130                if path.leading_colon.is_none()
131                    && path.segments.len() == 1
132                    && path.segments[0].ident == "Option" => {}
133            _ => return,
134        }
135        let attr = parse_quote!(
136            #[serde(default, skip_serializing_if = "Option::is_none", deserialize_with="crate::fallible_options::deserialize")]
137        );
138        field.attrs.push(attr);
139    }
140
141    if let Ok(mut input) = syn::parse::<ItemStruct>(input.clone()) {
142        apply_on_fields(&mut input.fields);
143        quote!(#input).into()
144    } else if let Ok(mut input) = syn::parse::<ItemEnum>(input) {
145        for variant in &mut input.variants {
146            apply_on_fields(&mut variant.fields);
147        }
148        quote!(#input).into()
149    } else {
150        panic!("with_fallible_options can only be applied to struct or enum definitions.");
151    }
152}