[−][src]Crate proc_macro_roids

Traits and functions to make writing proc macros more ergonomic.

The roids name is chosen because, although these functions make it easy to perform certain operation, they may not necessarily be a good idea =D!

Makes writing procedural macros much easier:

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro2::Span;
use proc_macro_roids::{DeriveInputStructExt, FieldExt, IdentExt};
use quote::quote;
use syn::{parse_macro_input, DeriveInput, Ident};

/// Derives a `Super` enum with a variant for each struct field:
///
/// ```rust,edition2018
/// use std::marker::PhantomData;
/// use super_derive::Super;
///
/// #[derive(Super)]
/// pub struct Man<T> {
///     #[super_derive(skip)]
///     name: String,
///     power_level: u64,
///     marker: PhantomData<T>,
/// }
/// ```
///
/// Generates:
///
/// ```rust,ignore
/// pub enum SuperMan {
///     U64(u64),
/// }
/// ```
#[proc_macro_derive(Super, attributes(super_derive))]
pub fn system_desc_derive(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as DeriveInput);
    let enum_name = ast.ident.prepend("Super");
    let fields = ast.fields();
    let relevant_fields = fields
        .iter()
        .filter(|field| !field.is_phantom_data())
        .filter(|field| !field.contains_tag("super_derive", "skip"));

    let variants = relevant_fields
        .map(|field| {
            let type_name = field.type_name();
            let variant_name = type_name.to_string().to_uppercase();
            let variant_name = Ident::new(&variant_name, Span::call_site());
            quote! {
                #variant_name(#type_name)
            }
        })
        .collect::<Vec<_>>();

    let token_stream2 = quote! {
        pub enum #enum_name {
            #(#variants,)*
        }
    };

    token_stream2.into()
}

Examples

Append additional #[derive(..)]s.

This works for function-like or attribute proc macros.

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro_roids::DeriveInputDeriveExt;
use quote::quote;
use syn::{parse_macro_input, parse_quote, DeriveInput};

#[proc_macro_attribute]
pub fn copy(_args: TokenStream, item: TokenStream) -> TokenStream {
    // Example input:
    //
    // #[derive(Debug)]
    // struct Struct;
    let mut ast = parse_macro_input!(item as DeriveInput);

    // Append the derives.
    let derives = parse_quote!(Clone, Copy);
    ast.append_derives(derives);

    // Example output:
    //
    // #[derive(Debug, Clone, Copy)]
    // struct Struct;
    TokenStream::from(quote! { #ast })
}

Append named fields.

This works for structs with named fields or unit structs.

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro_roids::FieldsNamedAppend;
use quote::quote;
use syn::{parse_macro_input, parse_quote, DeriveInput, FieldsNamed};

/// Example usage:
///
/// ```rust
/// use macro_crate::append_cd;
///
/// #[append_cd]
/// struct StructNamed { a: u32, b: i32 }
/// ```
#[proc_macro_attribute]
pub fn append_cd(_args: TokenStream, item: TokenStream) -> TokenStream {
    // Example input:
    //
    // struct StructNamed { a: u32, b: i32 }
    let mut ast = parse_macro_input!(item as DeriveInput);

    // Append the fields.
    let fields_additional: FieldsNamed = parse_quote!({ c: i64, d: usize });
    ast.append_named(fields_additional);

    // Example output:
    //
    // struct StructNamed { a: u32, b: i32, c: i64, d: usize }
    TokenStream::from(quote! { #ast })
}

Append unnamed fields (tuples).

This works for structs with unnamed fields or unit structs.

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro_roids::FieldsUnnamedAppend;
use quote::quote;
use syn::{parse_macro_input, parse_quote, DeriveInput, FieldsUnnamed};

/// Example usage:
///
/// ```rust
/// use macro_crate::append_i64_usize;
///
/// #[append_i64_usize]
/// struct StructUnit;
/// ```
#[proc_macro_attribute]
pub fn append_i64_usize(_args: TokenStream, item: TokenStream) -> TokenStream {
    // Example input:
    //
    // struct StructUnit;
    let mut ast = parse_macro_input!(item as DeriveInput);

    // Append the fields.
    let fields_additional: FieldsUnnamed = parse_quote!((i64, usize));
    ast.append_unnamed(fields_additional);

    // Example output:
    //
    // struct StructUnit(i64, usize);
    TokenStream::from(quote! { #ast })
}

Get newtype inner Field.

This works for structs with unnamed fields or unit structs.

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro_roids::DeriveInputNewtypeExt;
use quote::quote;
use syn::{parse_macro_input, parse_quote, DeriveInput, Type};

#[proc_macro_derive(Deref)]
pub fn derive_deref(item: TokenStream) -> TokenStream {
    // Example input:
    //
    // #[derive(Deref)]
    // struct Newtype(u32);
    let mut ast = parse_macro_input!(item as DeriveInput);

    // Get the inner field.
    let inner_field = ast.inner_type();

    // Implement `Deref`
    let type_name = &ast.ident;
    let token_stream_2 = quote! {
        #ast

        impl std::ops::Deref for #type_name {
            type Target = #inner_type;
            fn deref(&self) -> &Self::Target {
                &self.0
            }
        }
    }
    TokenStream::from(token_stream_2)
}

Ident concatenation.

use proc_macro_roids::IdentExt;
use proc_macro2::Span;
use syn::Ident;

let one = Ident::new("One", Span::call_site());
assert_eq!(Ident::new("OneSuffix", Span::call_site()), one.append("Suffix"));
assert_eq!(Ident::new("PrefixOne", Span::call_site()), one.prepend("Prefix"));

let two = Ident::new("Two", Span::call_site());
assert_eq!(Ident::new("OneTwo", Span::call_site()), one.append(&two));
assert_eq!(Ident::new("TwoOne", Span::call_site()), one.prepend(&two));

Accessing struct fields.

use proc_macro_roids::DeriveInputStructExt;
use syn::{parse_quote, DeriveInput, Fields};

let ast: DeriveInput = parse_quote! {
    struct Named {}
};

if let Fields::Named(..) = ast.fields() {
    // do something
}

Inspecting Fields.

use proc_macro_roids::FieldExt;
use syn::{parse_quote, Fields, FieldsNamed};

let fields_named: FieldsNamed = parse_quote! {{
    #[my_derive(tag_name)]
    pub name: PhantomData<T>,
}};
let fields = Fields::from(fields_named);
let field = fields.iter().next().expect("Expected field to exist.");

assert_eq!(field.type_name(), "PhantomData");
assert!(field.is_phantom_data());
assert!(field.contains_tag("my_derive", "tag_name"));

Traits

DeriveInputDeriveExt	Functions to make it ergonomic to work with `struct` ASTs.
DeriveInputNewtypeExt	Functions to make it ergonomic to work with newtype `struct` ASTs.
DeriveInputStructExt	Functions to make it ergonomic to work with `struct` ASTs.
FieldExt	Functions to make it ergonomic to inspect `Field`s and their attributes.
FieldsNamedAppend	Indicates this type may have `FieldsNamed` appended to it.
FieldsUnnamedAppend	Indicates this type may have `FieldsUnnamed` appended to it.
IdentExt	Convenience methods on `Ident`s.

Functions

ident_concat	Returns an `Ident` by concatenating `String` representations.
meta_list_contains	Returns whether the `MetaList` contains the specified `NestedMeta`.
nested_meta_to_ident	Returns the `Ident` of a nested meta. If it is a literal, `None` is returned.