5aa520eac0
# Objective `#[derive(Reflect)]` derives `Typed` impls whose `type_info` methods contain useless calls to `with_custom_attributes` and `with_docs`, e.g.: ``` ::bevy::reflect::NamedField:🆕:<f32>("x") .with_custom_attributes( ::bevy::reflect::attributes::CustomAttributes::default() ) .with_docs(::core::option::Option::None), ``` This hurts compile times and makes the `cargo expand` output harder to read. It might also hurt runtime speed, depending on whether the compiler can optimize away the no-op methods. Avoiding this will help with #19873. ## Solution Check if the attributes/docs are empty before appending the method calls. ## Testing I used `cargo expand` to confirm the useless calls are no longer produced. `-Zmacro-stats` outputs tells me this reduces the size of the `Reflect` impls produced for `bevy_ui` from 1_544_696 bytes to 1_511_214 bytes, a 2.2% drop. Only a small improvement, but it's a start.
84 lines
2.4 KiB
Rust
84 lines
2.4 KiB
Rust
//! Contains code related to documentation reflection (requires the `documentation` feature).
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use bevy_macro_utils::fq_std::FQOption;
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use proc_macro2::TokenStream;
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use quote::{quote, ToTokens};
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use syn::{Attribute, Expr, ExprLit, Lit, Meta};
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/// A struct used to represent a type's documentation, if any.
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///
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/// When converted to a [`TokenStream`], this will output an `Option<String>`
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/// containing the collection of doc comments.
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#[derive(Default, Clone)]
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pub(crate) struct Documentation {
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docs: Vec<String>,
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}
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impl Documentation {
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/// Create a new [`Documentation`] from a type's attributes.
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///
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/// This will collect all `#[doc = "..."]` attributes, including the ones generated via `///` and `//!`.
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pub fn from_attributes<'a>(attributes: impl IntoIterator<Item = &'a Attribute>) -> Self {
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let docs = attributes
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.into_iter()
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.filter_map(|attr| match &attr.meta {
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Meta::NameValue(pair) if pair.path.is_ident("doc") => {
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if let Expr::Lit(ExprLit {
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lit: Lit::Str(lit), ..
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}) = &pair.value
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{
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Some(lit.value())
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} else {
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None
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}
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}
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_ => None,
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})
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.collect();
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Self { docs }
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}
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/// The full docstring, if any.
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pub fn doc_string(&self) -> Option<String> {
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if self.docs.is_empty() {
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return None;
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}
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let len = self.docs.len();
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Some(
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self.docs
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.iter()
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.enumerate()
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.map(|(index, doc)| {
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if index < len - 1 {
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format!("{doc}\n")
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} else {
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doc.to_owned()
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}
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})
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.collect(),
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)
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}
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/// Is the collection empty?
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pub fn is_empty(&self) -> bool {
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self.docs.is_empty()
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}
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/// Push a new docstring to the collection
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pub fn push(&mut self, doc: String) {
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self.docs.push(doc);
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}
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}
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impl ToTokens for Documentation {
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fn to_tokens(&self, tokens: &mut TokenStream) {
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if let Some(doc) = self.doc_string() {
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quote!(#FQOption::Some(#doc)).to_tokens(tokens);
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} else {
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quote!(#FQOption::None).to_tokens(tokens);
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}
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}
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}
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