getters_by_type/lib.rs
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//!
//! This crate provides [`GettersByType`](derive.GettersByType.html) derive macro for structs, which implements a getter method for each type they contain.
//!
//! The generated methods start with the prefix `get_fields_` and end with a transcription of the type they refer.
//!
//! Example using `GettersByType` :
//!
//! ```rust
//! use getters_by_type::GettersByType;
//! #[derive(GettersByType)]
//! struct Foo {
//! first: i32,
//! second: i32,
//! third: i32,
//! }
//!
//! let object = Foo { first: 6, second: 12, third: 24 };
//!
//! // Let's sum all the i32 fields with a fold expression:
//! assert_eq!(object.get_fields_i32().iter().fold(0, |acc, x| **x + acc), 42);
//! ```
//!
//! As you notice, the getter methods return an array containing references to all the fields of the same type.
//! In that example, the return type of the method `get_fields_i32` would be `[&i32; 3]`.
//!
//! This crate also provides a `mut` version [`GettersMutByType`](derive.GettersMutByType.html) which also adds a mut version for those methods.
//!
//! In this case, the generated methods start with the prefix `get_mut_fields_` instead.
//!
//! Example using `GettersMutByType` :
//!
//!
//! ```rust
//! use getters_by_type::GettersMutByType;
//!
//! #[derive(Default)]
//! struct Updater {}
//! impl Updater {
//! fn update(&mut self) {/*...*/}
//! }
//!
//! #[derive(GettersMutByType, Default)]
//! struct Foo {
//! first: Updater,
//! second: Updater,
//! /*...*/
//! onehundredth: Updater,
//! }
//!
//! let mut object = Foo::default();
//!
//! // Let's update all the Updater fields
//! for updater in object.get_mut_fields_updater().iter_mut() {
//! updater.update();
//! }
//! ```
//!
//! In this example, the return type of the method `get_mut_fields_updater` would be `[&mut Updater; 3]`.
//! There is no dynamic memory allocation happening within the getter methods, as they just return a fixed array with references.
//! There isn't also unsafe code being generated.
//! For more documentation and examples, see each respective documentation section.
extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::{Span, TokenTree};
use quote::quote;
use std::collections::HashMap;
/// The `GettersByType` macro automatically generates an `impl` for the given struct,
/// implementing a getter method for each different type contained within the struct.
///
/// The generated methods start with the prefix `get_fields_` and end with a transcription of the type they refer.
///
/// Example:
///
/// ```rust
/// use getters_by_type::GettersByType;
/// #[derive(GettersByType)]
/// struct Foo {
/// a: String,
/// b: String,
/// }
///
/// // Would generete:
///
/// impl Foo {
/// fn get_fields_string(&self) -> [&String; 2] {
/// [&self.a, &self.b]
/// }
/// }
/// ```
///
/// As you notice, the chars of all the types (`String` in this case) go
/// to the method signature in lowercase form.
///
/// It works the same with generic, reference and other types, with the following exceptions:
/// 1. Characters `<` `>` `(` `)` `[` `]` `,` `;` always get converted to `_`.
/// 2. Return type arrow `->` and reference character `&` get ignored completely.
/// 3. Pointer types `*const` and `*mut` get converted o `ptr_const_` and `ptr_mut_` respectively.
///
/// Also, reference types and non-reference types will be covered by the same
/// method, as the methods are always returning references in the first place.
///
/// Example for fn, generic and reference types (more examples for other types later):
///
/// ```rust
/// use getters_by_type::GettersByType;
/// #[derive(GettersByType)]
/// struct Foo {
/// a: Result<i32, i32>,
/// b: Result<i32, Result<i32, i32>>,
/// c: fn(usize) -> f32,
/// d: &'static bool,
/// e: bool,
/// }
///
/// // Would generate:
///
/// impl Foo {
/// fn get_fields_result_i32_i32_(&self) -> [&Result<i32, i32>; 1] {
/// [&self.a]
/// }
/// fn get_fields_result_i32_result_i32_i32__(&self) -> [&Result<i32, Result<i32, i32>>; 1] {
/// [&self.b]
/// }
/// fn get_fields_fn_usize___f32(&self) -> [&fn(usize) -> f32; 1] {
/// [&self.c]
/// }
/// fn get_fields_bool(&self) -> [&bool; 2] {
/// [&self.d, &self.e]
/// }
/// }
/// ```
///
/// Other examples of types to method signature conversions here:
///
/// ```rust
/// use getters_by_type::GettersByType;
/// #[derive(GettersByType)]
/// struct Foo<'a> {
/// a: &'a str,
/// b: Box<Fn(i32) -> f32>,
/// c: &'a Vec<&'a Option<&'a i32>>,
/// d: Result<i32, Result<i32, Result<i32, &'static str>>>,
/// e: Option<Option<Option<Option<Option<fn(usize)>>>>>,
/// f: (i32, i32),
/// g: [i32; 2],
/// h: &'a [&'a Option<&'a i32>],
/// i: *const i32,
/// j: *mut i32,
/// k: Box<dyn Bar>,
/// }
/// trait Bar {}
/// impl Bar for i32 {}
/// let vector = vec!();
/// let number_1 = 1;
/// let mut number_2 = 2;
/// let o = Foo {
/// a: "",
/// b: Box::new(|_| 0.0),
/// c: &vector,
/// d: Ok(0),
/// e: None,
/// f: (0, 0),
/// g: [0, 0],
/// h: vector.as_slice(),
/// i: &number_1,
/// j: &mut number_2,
/// k: Box::new(0),
/// };
/// // from type: &'a str
/// o.get_fields_str();
/// // from type: Box<Fn(i32) -> f32>
/// o.get_fields_box_fn_i32_f32_();
/// // from type: &'a Vec<&'a Option<&'a i32>>
/// o.get_fields_vec_option_i32__();
/// // from type: Result<i32, Result<i32, Result<i32, &'static str>>>
/// o.get_fields_result_i32_result_i32_result_i32_str___();
/// // from type: Option<Option<Option<Option<Option<fn(usize)>>>>>
/// o.get_fields_option_option_option_option_option_fn_usize______();
/// // from type: (i32, i32)
/// o.get_fields__i32_i32_();
/// // from type: [i32; 2]
/// o.get_fields__i32_2_();
/// // from type: &'a [&'a Option<&'a i32>]
/// o.get_fields__option_i32__();
/// // from type: *const i32
/// o.get_fields_ptr_const_i32();
/// // from type: *mut i32
/// o.get_fields_ptr_mut_i32();
/// // from type: Box<dyn Bar>
/// o.get_fields_box_dyn_bar_();
/// ```
///
/// Method visibility is inherited directly from the struct visibility,
/// so if the struct is public, all the methods generated by `GettersByType`
/// will be public too. There is no fine-grained control for fields visibility.
///
/// There are still some types not implemented. Those are the following:
///
/// * `TraitObject` is partially implemented, `Box<dyn Trait>` works, but `&dyn Trait` doesn't.
/// * `Never`
/// * `ImplTrait`
/// * `Group`
/// * `Infer`
/// * `Macro`
/// * `Verbatim`
///
/// Hopefully, they will get implemented in next releases.
///
#[proc_macro_derive(GettersByType)]
pub fn getters_by_type(input: TokenStream) -> TokenStream {
ImplContext::new(input, "GettersByType", false).transform_ast()
}
/// The `GettersMutByType` macro automatically generates an `impl` for the given struct,
/// implementing a getter method for each different type contained within the struct.
///
/// The generated methods start with the prefix `get_mut_fields_` and end with a transcription of the type they refer.
///
/// Example:
///
/// ```rust
/// use getters_by_type::GettersMutByType;
/// #[derive(GettersMutByType)]
/// struct Foo {
/// a: String,
/// b: String,
/// }
///
/// // Would generete:
///
/// impl Foo {
/// fn get_mut_fields_string(&mut self) -> [&mut String; 2] {
/// [&mut self.a, &mut self.b]
/// }
/// }
/// ```
///
/// This is the mutable version of `GettersByType`.
/// The same rules are applying, so check the [GettersByType derive](derive.GettersByType.html) documentation first.
///
/// There is one important difference, thought. There are some fields with types that
/// can't be made mutable. I.e. types with immutable references. When that's the case,
/// the field gets ignored completely.
///
/// Example:
///
/// ```rust
/// use getters_by_type::GettersMutByType;
/// #[derive(GettersMutByType)]
/// struct Foo<'a> {
/// a: &'a String,
/// b: String,
/// }
///
/// let string = String::new();
/// let mut o = Foo {
/// a: &string,
/// b: "".into(),
/// };
///
/// assert_eq!(o.get_mut_fields_string().len(), 1); // instead of 2
/// ```
#[proc_macro_derive(GettersMutByType)]
pub fn getters_mut_by_type(input: TokenStream) -> TokenStream {
ImplContext::new(input, "GettersByMutType", true).transform_ast()
}
struct ImplContext {
ast: syn::DeriveInput,
derive_name: &'static str,
with_mutability: bool,
}
impl ImplContext {
fn new(input: TokenStream, derive_name: &'static str, with_mutability: bool) -> ImplContext {
ImplContext {
ast: syn::parse(input).expect("Could not parse AST."),
derive_name,
with_mutability,
}
}
fn transform_ast(&self) -> TokenStream {
let fields_by_type = match self.ast.data {
syn::Data::Struct(ref class) => self.read_fields(&class.fields),
_ => panic!(
"The type '{}' is not a struct but tries to derive '{}' which can only be used on structs.",
self.ast.ident, self.derive_name
),
};
let mut methods = Vec::<TokenTree>::new();
for (type_pieces, fields_sharing_type) in fields_by_type.into_iter() {
let return_type = MethodReturnType {
ty: fields_sharing_type.ty,
name: make_type_name_from_type_pieces(type_pieces),
};
methods.extend(self.make_method_tokens("get_fields", &return_type, false, fields_sharing_type.immutable_fields));
if self.with_mutability {
methods.extend(self.make_method_tokens("get_mut_fields", &return_type, true, fields_sharing_type.mutable_fields));
}
}
let (ty, generics) = (&self.ast.ident, &self.ast.generics);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let tokens = quote! {
impl #impl_generics #ty #ty_generics
#where_clause
{
#(#methods)
*
}
};
tokens.into()
}
fn read_fields<'a>(&self, fields: &'a syn::Fields) -> HashMap<Vec<TypePart<'a>>, FieldsSharingType<'a>> {
let mut fields_by_type = HashMap::<Vec<TypePart>, FieldsSharingType>::new();
for field in fields.iter() {
if let Some(ref ident) = field.ident {
let info = get_info_from_type(&field.ty);
match make_idents_from_type(&field.ty) {
Ok(type_pieces) => {
let fields_by_type = fields_by_type.entry(type_pieces).or_insert_with(|| FieldsSharingType::new(info.ty));
if info.is_mutable && self.with_mutability {
fields_by_type.mutable_fields.push(ident);
}
fields_by_type.immutable_fields.push(ident);
}
Err(err) => {
eprintln!("[WARNING::{}] Field '{}' of struct '{}' not covered because: {}", self.derive_name, ident, self.ast.ident, err);
}
}
}
}
fields_by_type
}
fn make_method_tokens(&self, method_prefix: &str, return_type: &MethodReturnType, mutability: bool, field_idents: Vec<&syn::Ident>) -> proc_macro2::TokenStream {
let count = field_idents.len();
let method_name = syn::Ident::new(&format!("{}_{}", method_prefix, return_type.name), Span::call_site());
let (vis, return_type) = (&self.ast.vis, &return_type.ty);
if mutability {
quote! {
#vis fn #method_name(&mut self) -> [&mut #return_type; #count] {
[#(&mut self.#field_idents),*]
}
}
} else {
quote! {
#vis fn #method_name(&self) -> [&#return_type; #count] {
[#(&self.#field_idents),*]
}
}
}
}
}
struct MethodReturnType<'a> {
ty: &'a syn::Type,
name: String,
}
struct FieldsSharingType<'a> {
immutable_fields: Vec<&'a syn::Ident>,
mutable_fields: Vec<&'a syn::Ident>,
ty: &'a syn::Type,
}
impl<'a> FieldsSharingType<'a> {
fn new(ty: &'a syn::Type) -> FieldsSharingType {
FieldsSharingType {
immutable_fields: vec![],
mutable_fields: vec![],
ty,
}
}
}
struct TypeInfo<'a> {
is_mutable: bool,
ty: &'a syn::Type,
}
#[derive(Hash, PartialEq, Eq)]
enum TypePart<'a> {
Ident(&'a syn::Ident),
Integer(u64),
Separator(&'static str),
}
impl<'a> TypePart<'a> {
fn to_string(&self) -> String {
match self {
TypePart::Ident(i) => i.to_string(),
TypePart::Separator(s) => s.to_string(),
TypePart::Integer(i) => i.to_string(),
}
}
}
fn get_info_from_type(ty: &syn::Type) -> TypeInfo {
let (ty, is_mutable) = match ty {
syn::Type::Reference(ref reference) => (&*reference.elem, reference.mutability.is_some()),
_ => (ty, true),
};
TypeInfo { is_mutable, ty }
}
fn make_idents_from_type<'a>(ty: &'a syn::Type) -> Result<Vec<TypePart<'a>>, &'static str> {
let mut type_pieces = Vec::<TypePart<'a>>::with_capacity(8);
fill_type_pieces_from_type(&mut type_pieces, ty)?;
Ok(type_pieces)
}
fn fill_type_pieces_from_type<'a>(type_pieces: &mut Vec<TypePart<'a>>, ty: &'a syn::Type) -> Result<(), &'static str> {
match ty {
syn::Type::Path(ref path) => fill_type_pieces_from_type_path(type_pieces, &path.path),
syn::Type::Reference(ref reference) => fill_type_pieces_from_type(type_pieces, &reference.elem),
syn::Type::BareFn(ref function) => {
type_pieces.push(TypePart::Separator("fn("));
fill_type_pieces_from_array_of_inputs(type_pieces, &function.inputs, ",", |type_pieces, arg| fill_type_pieces_from_type(type_pieces, &arg.ty))?;
type_pieces.push(TypePart::Separator(")"));
fill_type_pieces_from_return_type(type_pieces, &function.output)?;
Ok(())
}
syn::Type::Slice(slice) => {
type_pieces.push(TypePart::Separator("["));
fill_type_pieces_from_type(type_pieces, &slice.elem)?;
type_pieces.push(TypePart::Separator("]"));
Ok(())
}
syn::Type::Array(array) => {
type_pieces.push(TypePart::Separator("["));
fill_type_pieces_from_type(type_pieces, &array.elem)?;
type_pieces.push(TypePart::Separator(";"));
match &array.len {
syn::Expr::Lit(lit) => match &lit.lit {
syn::Lit::Int(int) => type_pieces.push(TypePart::Integer(int.value())),
_ => return Err("syn::Lit::* are not implemented yet."),
},
_ => return Err("syn::Expr::* are not implemented yet."),
}
type_pieces.push(TypePart::Separator("]"));
Ok(())
}
syn::Type::Tuple(tuple) => {
type_pieces.push(TypePart::Separator("("));
fill_type_pieces_from_array_of_inputs(type_pieces, &tuple.elems, ",", fill_type_pieces_from_type)?;
type_pieces.push(TypePart::Separator(")"));
Ok(())
}
syn::Type::Paren(paren) => {
type_pieces.push(TypePart::Separator("("));
fill_type_pieces_from_type(type_pieces, &paren.elem)?;
type_pieces.push(TypePart::Separator(")"));
Ok(())
}
syn::Type::Ptr(ptr) => {
type_pieces.push(TypePart::Separator("ptr_"));
if ptr.const_token.is_some() {
type_pieces.push(TypePart::Separator("const_"));
}
if ptr.mutability.is_some() {
type_pieces.push(TypePart::Separator("mut_"));
}
fill_type_pieces_from_type(type_pieces, &ptr.elem)?;
Ok(())
}
syn::Type::ImplTrait(_) => Err("syn::Type::ImplTrait can not be implemented."), // ImplTrait is not valid outside of functions and inherent return types, so can't be implemented.
syn::Type::TraitObject(trait_object) => {
if trait_object.dyn_token.is_some() {
type_pieces.push(TypePart::Separator("dyn_"));
}
fill_type_pieces_from_array_of_inputs(type_pieces, &trait_object.bounds, "+", |type_pieces, bound| match bound {
syn::TypeParamBound::Trait(trait_bound) => fill_type_pieces_from_type_path(type_pieces, &trait_bound.path),
syn::TypeParamBound::Lifetime(_) => Ok(()),
})
}
syn::Type::Never(_) => Err("syn::Type::Never is not implemented yet."),
syn::Type::Group(_) => Err("syn::Type::Group is not implemented yet."),
syn::Type::Infer(_) => Err("syn::Type::Infer is not implemented yet."),
syn::Type::Macro(_) => Err("syn::Type::Macro is not implemented yet."),
syn::Type::Verbatim(_) => Err("syn::Type::Verbatim is not implemented yet."),
}
}
fn fill_type_pieces_from_type_path<'a>(type_pieces: &mut Vec<TypePart<'a>>, path: &'a syn::Path) -> Result<(), &'static str> {
for segment in path.segments.iter() {
type_pieces.push(TypePart::Ident(&segment.ident));
fill_type_pieces_from_path_arguments(type_pieces, &segment.arguments)?;
}
Ok(())
}
fn fill_type_pieces_from_path_arguments<'a>(type_pieces: &mut Vec<TypePart<'a>>, arguments: &'a syn::PathArguments) -> Result<(), &'static str> {
match arguments {
syn::PathArguments::AngleBracketed(ref angle) => {
type_pieces.push(TypePart::Separator("<"));
fill_type_pieces_from_array_of_inputs(type_pieces, &angle.args, ",", |type_pieces, arg| match arg {
syn::GenericArgument::Type(ref ty) => fill_type_pieces_from_type(type_pieces, ty),
syn::GenericArgument::Lifetime(_) => Ok(()),
syn::GenericArgument::Binding(_) => Ok(()),
syn::GenericArgument::Constraint(_) => Ok(()),
syn::GenericArgument::Const(_) => Ok(()),
})?;
type_pieces.push(TypePart::Separator(">"));
}
syn::PathArguments::None => {}
syn::PathArguments::Parenthesized(ref paren) => {
type_pieces.push(TypePart::Separator("("));
fill_type_pieces_from_array_of_inputs(type_pieces, &paren.inputs, ",", fill_type_pieces_from_type)?;
type_pieces.push(TypePart::Separator(")"));
fill_type_pieces_from_return_type(type_pieces, &paren.output)?;
}
}
Ok(())
}
fn fill_type_pieces_from_return_type<'a>(type_pieces: &mut Vec<TypePart<'a>>, output: &'a syn::ReturnType) -> Result<(), &'static str> {
match output {
syn::ReturnType::Default => Ok(()),
syn::ReturnType::Type(_, ref arg) => fill_type_pieces_from_type(type_pieces, &**arg),
}
}
fn fill_type_pieces_from_array_of_inputs<'a, T, U>(
type_pieces: &mut Vec<TypePart<'a>>,
inputs: &'a syn::punctuated::Punctuated<T, U>,
separator: &'static str,
action: impl Fn(&mut Vec<TypePart<'a>>, &'a T) -> Result<(), &'static str>,
) -> Result<(), &'static str> {
if !inputs.is_empty() {
for arg in inputs {
action(type_pieces, arg)?;
match type_pieces[type_pieces.len() - 1] {
TypePart::Separator(_s) if _s == separator => {}
_ => type_pieces.push(TypePart::Separator(separator)),
}
}
match type_pieces[type_pieces.len() - 1] {
TypePart::Separator(_s) if _s == separator => type_pieces.truncate(type_pieces.len() - 1),
_ => {}
}
}
Ok(())
}
fn make_type_name_from_type_pieces(type_pieces: Vec<TypePart>) -> String {
type_pieces
.into_iter()
.map(|piece| piece.to_string())
.collect::<String>()
.to_lowercase()
.chars()
.map(|c| match c {
'<' | '>' | '(' | ')' | '[' | ']' | '-' | ',' | ';' => '_',
_ => c,
})
.collect()
}